VACUUM FURNACES TECHNICAL CONTENT Archives

Pit LPC: A Modern Take on High Throughput Heat Treat

Producing durable, wear-resistant gears for the wind turbine industry requires exacting control of carbon diffusion. Modern low pressure carburizing (LPC) is pushing the boundaries of control and consistency. This technology fine tunes carbon diffusion into the surface of components, and applied in a new pit-style vacuum furnace, it also delivers temperature uniformity, stronger gears, and shorter cycle times for large, complex components, all while eliminating oxidation and direct CO₂ emissions. In this Technical Tuesday installment, Tom Hart, director of sales for North America at SECO/WARWICK Corporation, examines how modern LPC technology in a pit-style vacuum furnace is reshaping high-volume carburizing for today’s in-house heat treaters.

This informative piece was first released in Heat Treat Today’s November 2025 Annual Vacuum Heat Treating print edition.

The Need To Carburize

Carburizing is a thermochemical treatment that finds applications across the automotive, aviation, and energy industries, particularly in power transmission systems. The widespread use of this process across many industries stems from its ability to improve mechanical properties by enriching the surface of steel with carbon.

Consider the wind turbine industry, growing with a CAGR (compound annual growth rate) of 6.2% from 2024 to 2033 (GlobeNewswire 2024). Carburizing plays a key role in the production of gears and pinions. These components, often made of alloy steels, such as 18CrNiMo7-6, 4320, 4820, and 9310 (GearSolutions 2009, Jantara 2019), must meet high strength and quality requirements. Carburized layers, often over 4 mm thick, provide resistance to wear and dynamic loads, which is important given the turbine’s expected service life of at least twenty years.

In practice, however, gears often require servicing after five to seven years (Jantara 2019), with their failures generating long downtimes and high costs (Perumal and Rajamani 2014).

Figure 1a: Pit-LPC in a hardening cell (model)

The carburizing process, combined with hardening (usually in oil) and tempering, increases:

Surface hardness: improving abrasian resistance
Core ductility: protecting against cracks
Fatigue strength: extending the life of the part, which translates into lower operating costs

Alternative technologies, such as nitriding or surface hardening, offer other benefits (e.g., reduced deformation), but have limitations, such as thinner hardened layers, relatively long nitriding process times, or difficulties with complex geometry for surface hardening.

Pit Meets Vacuum LPC

Traditional atmospheric carburizing, despite its established position, has reached its limits in process performance expectations. In response to market needs, LPC (low pressure carburizing) technology is being increasingly implemented to enable precise process control, reduced emissions, and improved energy efficiency. More specifically, a pit furnace with vacuum heat treatment capabilities, aka the Pit-LPC, has been designed and developed to carburize thick layers on very large and/or long parts. This furnace combines the advantages of LPC technology with the ability to integrate existing hardening cells, facilitating the modernization of older installations.

While a vacuum furnace opening to an air atmosphere is a feature previously reserved for atmospheric furnaces, this innovative pit furnace has ceramic insulation and a dedicated heating system to leverage this capability. The chamber door can therefore be opened at process temperature in an air atmosphere for the direct transfer of the charge to the hardening tank. Additionally, the furnace is equipped with a closed circuit forced cooling system, which significantly shortens the charge cooling time from the carburizing temperature to the hardening temperature, increasing efficiency and shortening the production cycle.

Furthermore, the furnace allows for the process to be carried out at temperatures of 1925°F (1050°C) and higher, significantly shortening carburizing time and reducing production costs, even while maintaining a safe level of grain growth (e.g., 1800°F (980°C)).

Benefits of LPC technology designed in a pit furnace include:

Reduced process time due to higher operating temperatures
Elimination of internal oxidation (IGO) in the carburizing process
Highly uniform carburized layer
Low process gas consumption
No direct CO₂ emissions and fire risk
Ready for operation without lengthy conditioning
Computer-aided process support

Additionally, the furnace design increases work safety and comfort in its elimination of open flames, risks of explosion, and the need for constant atmospheric monitoring.

Figure 2. SimVac program window with an example LPC process simulation

This new pit furnace is compatible with SimVac software, developed by Lodz University of Technology and SECO/WARWICK, which enables the simulation and optimization of LPC parameters, reducing the need for process tests. SimVac Plus is a simulation software that includes a vacuum carburizing module (Figure 2). The program can be used either as a standalone tool for designing processes based on the desired carburized layer requirements or to visualize the effect of a given boost/diffusion sequence in the form of a carbon profile.

Testing the Furnace Characteristics and Technical Parameters

The furnace was designed to meet the highest requirements for heat treatment equipment. The basic technical parameters are as follows:

Working space / charge weight: 71″ diameter x 118″ deep / 17,600 lb (1,800 mm x 3,000mm deep / 8,000 kg)
Operating temperature: up to 2010°F (1100°C)
Heating power: 360 kW, three independent zones
Vacuum level: 10⁻² torr
Carburizing gas: acetylene

Temperature Uniformity

Temperature distribution tests were conducted in the furnace, with 12 load thermocouples arranged according to the diagram shown in Figure 2. Measurements were taken at several temperatures under vacuum conditions. The purpose of the tests was to confirm compliance with the Class 1 ±5°F (3°C) requirements of the AMS2750 standard.

Figures 3a-d. Location of the TUS load thermocouples and the results in vacuum at temperatures of 1550°F (840°C), 1800 °F (980°C), and 1925°F (1050°C)

The results presented in Figure 3 indicate that the furnace provides above-average temperature uniformity, which is particularly important for a large workspace with 71″ diameter x 118″ deep (1,800 mm diameter × 3,000 mm deep) and the processing of large-sized components with thick layers. The temperature difference (ΔT) between the extreme thermocouples, measured at 1550°F (840°C), 1800 °F (980°C), and 1925°F (1050°C), did not exceed 3.5°F (2°C). This means that the furnace meets the Class 1 requirements of the AMS2750 standard by a wide margin.

Operational Dynamics

Additionally, to evaluate the furnace’s operational dynamics, heating and cooling tests were performed on an empty device with samples. Figure 4a shows the heating curve; the furnace reaches a temperature of 1800°F (980°C) in 60 minutes. The furnace’s high energy efficiency has a heat loss of just 32 kW under these circumstances.

Figure 4b shows teh curve of cooling forced by nitrogen at atmospheric pressure, measured in three zones and on samples with diameters of 1″ (25 mm) and 4″ (100 mm). The temperature drops from 1800°F (980°C) to 575°F (300°C) in 60 minutes; reaching 210°F (100°C) takes only two hours, whereas natural cooling would take several days.

Vacuum tests show that the furnace reaches operating vacuum of 10⁻¹ hPa in under 30 minutes and has a leakage rate of 10⁻³ mbar·l/s, which meets the industry standard for vacuum furnaces.

Test of Atmosphere vs. Vacuum Carburizing Processes

To obtain a carburized layer 0.145–0.160″ (3.7–4.0 mm) thick for 52.3 HRC (550HV1), two tests were compared: one in the PEGAT atmosphere furnace (Figure 5a) and another in the Pit-LPC vacuum furnace (Figure 5b). In both cases, the charge consisted of seven gears made of 18CrNiMo7-6 material, with a total weight of approximately 6.5 tons and a surface area of 280 ft² (26 m²). The process consisted of three stages:

Stage I: heating to the carburizing temperature and soaking
Stage II: actual carburizing with cooling to the hardening temperature and holding
Stage III: hardening in an external quenching tank — identical in both processes

Table A. Atmosphere vs. Vacuum Carburizing Process Comparison

Figure 5a. Essential process data and schematic flow of the carburizing process in a PEGAT atmosphere furnace

The LPC process, which consists of saturation and diffusion segments (Figure 6) allows for the precise control of carbon distribution. As the process progresses, the duration of the diffusion segments is extended, ensuring uniform saturation of the material.

Figure 6. Vacuum carburizing process trends in the Pit-LPC

After carburizing and hardening, all components were tempered at 355°F (180°C) for three hours.

Metallurgical Results: Gears & Samples Destructive Testing

Table B. Chemical Composition of 18CrNiMo7-6 (according to EN10084)

Gears and samples made of 18CrNiMo7-6 steel were used for destructive testing, in accordance with the EN 10084 standard. Six cylindrical samples were placed throughout the workspace — inside and outside the part — to assess carburization uniformity.

Tests conducted:

Vickers microhardness (HV1): performed on a Struers Durascan 70 device, allowing for the determination of hardness profiles and carburized layer depth (ECD) — a load of 9.81 N (HV1).
Surface and core hardness (Rockwell): measurements were performed on a Wilson Wolpert TESTOR tester with a load of 1470.1 N. At least five measurements were taken for each sample.
Microstructure: assessed on a Nikon LV150 optical microscope after nital etching.
Internal oxidation (IGO): analyzed on the unetched surface of the microsection.

Figures 7a-f. Microhardness profiles after the full process (carburizing, hardening, and tempering)

Figure 7 shows the microhardness profiles for the tested samples. For each sample, microhardness paths were inspected in three cross-sections. Based on this, the effective ECD layer thickness obtained on each sample was determined, as presented in Table C.

Table C. Thickness of the Carburized Layer Read from the Microhardness Charts (effective case depth average is 0.145–0.160″ (3.7–4.0 mm) at 52.3 HRC (550 HV1))

Average ECD values obtained for the samples ranged from 0.148 to 0.154″ (3.77 to 3.91 mm).

Surface and core hardness values for all samples were consistent and typical of carburized layers (Table D). Surface hardness ranged from 61.0 to 63.2 HRC and core hardness from 39.9 to 40.7 HRC. Interestingly, samples located on the inner side of the wheel achieved slightly higher surface hardness values (caused by retained austenite and cooling intensity).

Table D. Measured values of surface hardness and core hardness

Microstructure images of low-tempered martensite, along with retained austenite, were identified, ranging from 17 to 20% (Figure 8). The amount of retained austenite was determined using NIS-Elements software. No variation in structure was observed depending on sample location.

Figure 8a. Exemplary post-processing microstructure pictures of sample 1 surface. Magnifications x100 (left) and x500 (right). Nital etching 2%. Martensite with residual austenite (approx. 18%).

The presence of intergranular oxidation (IGO) was also inspected, averaging 5.5 μm throughout the tested samples. For comparison, intergranular oxidation in the atmospheric process averages above 15 μm. In the new LPC pit furnace, internal oxidation only occurs during unloading and transfer of the charge to the hardening tank, whereas in the atmospheric furnace, the presence of oxygen in the carburizing atmosphere is also significant, significantly increasing the IGO value.

The level of hardening deformation after the process conducted in the new LPC pit furnace and the atmosphere furnace is comparable due to the use of the same hardening tank in both devices and the absence of the carburizing process.

Comparison of Process Economics

Economic aspects play a key role in modern heat and thermochemical processing. Therefore, the consumption of basic utilities was compared for the reference processes (described in Chapter 5), resulting in a 0.152″ (3.8 mm) thick hardened layer. The analysis included a Pit-LPC and a PEGAT-type atmospheric furnace, both with identical workspace and the same charge. In addition, the LPC process was simulated at 1900°F (1040°C). The results are summarized in Table E.

Table E. Comparison of utility consumption and costs

The results show that the new LPC furnace model consumes significantly less electricity by approximately 57%, which translates into a lower carbon footprint, especially when energy is derived from fossil fuels. Nitrogen consumption is comparable, with a slight advantage for the Pit-LPC (savings of up to 10%).

The largest differences are found in carburizing gases. The atmospheric furnace consumes 9,900 ft³ (280 m³) of methane — approximately 440 lb (200 kg) and an additional 4.4–13.2 lb (2–6 kg) of propane per process. In the LPC furnace, acetylene consumption is reduced to 39.2 lb (17.8 kg) because carburizing gas only flows during the boost phase.

Importantly, the LPC process does not generate direct CO₂ emissions, unlike an atmospheric furnace, which emits approximately 1325 lb (600 kg) of CO₂ per cycle. Cooling water consumption in the new LPC furnace is also reduced by over 45%.

The presented comparison of utility consumption in the two types of furnaces directly translates into the economic aspects of using these devices and conducting production processes. For cost comparison purposes, the following unit utility costs were assumed, as presented in Table F:

Table F. Unit costs of energy factors and technological gases according to European averages

In summary, the total utility costs for the process conducted in the Pit-LPC at 1800°F (980°C) are 53% lower compared to an atmospheric furnace conducted at 1700°F (925°C). At a temperature of 1925°F (1040°C), savings reach 60%. These savings are primarily due to lower energy and process gas consumption. Furthermore, the lack of CO₂ emissions eliminates the need to pay emission fees.

The efficiency of this furnace is almost twice as much at 1795°F (980°C) and three times as much at 1925°F (1040°C) compared to an atmospheric furnace.

Summary

The new Pit-LPC vacuum furnace combines the design features of a top-loaded pit and performs carburizing using vacuum technology instead of atmospheric technology. Bringing higher processing temperatures than traditional atmospheric furnaces to the market, as well as the ability to open hot in an air atmosphere, this technology proves that direct transfer of the charge to the hardening tank is possible in vacuum furnaces.

Another key development, this design significantly shortens carburizing time compared to atmosphere furnaces since the furnace can operate under vacuum, inert gas (nitrogen, argon), air, and carburizing gases, at temperatures up to 2010°F (1100°C).

Since this new pit furnace design does not require the use a retort or atmosphere mixer, which are the most vulnerable components inside a traditional atmospheric furnace, the furnace operates with greater reliability and lower costs. Furthermore, an efficient and robust vacuum pumping system provides the vacuum environment and operational readiness in less than 30 minutes. Time is also saved by the integrated closed-loop gas cooling system that shortens cooling time: dropping temperatures from 1800°F (980°C) to 1545°F (840°C) in 30 minutes for a full charge and to 210°F (100°C) in two hours for an empty furnace, operations which would take several hours and days respectively in atmosphere furnaces.

The advanced thermal insulation and a uniform heating element layout ensure high energy efficiency and precise temperature uniformity in the working space, yielding additional cost and energy savings.

This carburizing process is based on FineCarb LPC technology and supported by the SimVac simulator, enabling precise carbon profile shaping and achieving layers 0.148–0.154″ (3.77–3.91 mm) thick with high repeatability.

With the ability to operate at temperatures up to 1925°F (1050°C), the new LPC pit-styled furnace significantly shortens process time, reduces utility consumption, and lowers operating costs by up to 50%, while increasing productivity by a factor of x2 to x3. One of these furnaces can replace two to three atmosphere furnaces of the same size.

Finally, the furnace operates in a safe and non-flammable atmosphere, emits no direct CO₂, and reduces energy consumption, making it an environmentally friendly solution.

Conclusions

The Pit-LPC furnace is a modern alternative to the traditional atmosphere furnace and offers a number of advantages in terms of quality, efficiency, safety, economy, and ecology. Providing an innovative solution for vacuum carburizing and meeting stringent carburization layer thickness guidelines, this design is a viable option to fully replace traditional atmospheric pit furnaces operating in a carburizing atmosphere.

References

GlobeNewswire. 2024. “Wind Turbine Market to Reach $115.2 Billion Globally by 2033 at 6.2% CAGR: Allied Market Research.” GlobeNewswire, September 18, 2024. https://www.globenewswire.com/news-release/2024/09/18/2948365/0/en/Wind-Turbine-Market-to-Reach-115-2-Billion-Globally-by-2033-at-6-2-CAGR-Allied-Market-Research.html

GearSolutions. 2009. “Carburizing Wind-Turbine Gears.” Gear Solutions, May 1, 2009. https://gearsolutions.com/features/carburizing-wind-turbine-gears/

Jantara, Valter Luiz Jr. 2019. “Wind Turbine Gearboxes: Failures, Surface Treatments and Condition Monitoring.” In Non-Destructive Testing and Condition Monitoring Techniques for Renewable Energy Industrial Assets, edited by Mayorkinos Papaelias, Fausto Pedro García Márquez, and Alexander Karyotakis. Amsterdam: Elsevier.

Perumal, S., and G. P. Rajamani. 2014. “Improving the Hardness of a Wind Turbine Gear Surface by Nitriding Process.” Applied Mechanics and Materials 591: 19–22.

Rolinski, Edward. 2016. “Modern Nitriding Techniques for Gear Applications.” Gear Solutions, March 16, 2016. https://gearsolutions.com/departments/hot-seat-modern-nitriding-techniques-for-gear-applications/

About The Author:

Tom Hart
Director of Sales for North America
SECO/WARWICK Corporation

Tom Hart joined SECO/WARWICK in 2011 as a sales engineer and has been in the precision manufacturing industry for over 16 years. His responsibilities have him caring for SECO/WARWICK’s clients and their various process and heat treatment equipment needs. Tom received his manufacturing engineering degree from Edinboro University of Pennsylvania, has authored numerous white papers, and is recognized throughout the heat treatment industry as a go-to-guy for thermal processing.

For more information: Contact Tom at Tom.Hart@SecoWarwick.com.

Pit LPC: A Modern Take on High Throughput Heat Treat Read More »

Heat Treat Radio #127: The Case for Modular Vacuum Heat Treating

November 20, 2025 / HARDENING TECHNICAL CONTENT, HEAT TREAT RADIO, MANUFACTURING HEAT TREAT TECH, QUENCHING TECHNICAL CONTENT, VACUUM FURNACES TECHNICAL CONTENT

In this episode of Heat Treat Radio, host Doug Glenn invites Dennis Beauchesne of ECM USA to explore the technology, benefits, scalability, and sustainability of modular heat treating systems. Together, they discuss how shared utilities, automated transfers, and adaptable heating cells can replace multiple standalone furnaces without compromising quality or precision. Learn how these systems streamline and simplify operations for future expansion — one cell at a time.

Below, you can watch the video, listen to the podcast by clicking on the audio play button, or read an edited transcript.

Heat Treat Today · Heat Treat Radio #127: The Case for Modular Vacuum Heat Treating

The following transcript has been edited for your reading enjoyment.

Introduction

Doug Glenn: I am very privileged to have with me today, Dennis Beauchesne from ECM USA. We’re going to be talking about modular heat treating systems, which is a growing category of equipment.

ECM Synergy Center (00:50)

Doug Glenn: Tell me about ECM’s Synergy Center, which is where you are at right now, on the shop floor.

The ECM Flex 600TG vacuum furnace located in the ECM Synergy Center Source: ECM USA

Dennis Beauchesne: I’m standing here in the middle of our Synergy Center. It’s about a 5,000-square-foot facility that is dedicated to proving out client parts for testing various processes, mostly LPC, but we also do a number of other processes here. We have a full metallurgical lab, 3D microscope, a number of tools, including a CMM that we can do before and after heat treat distortion testing for clients that want to know how much their parts move.

It’s a dedicated center just for clients to use. We also use the center for pre-completion of installations, final testing, and training, such as training on maintenance, understanding the software, and how everything works together.

Doug Glenn: It’s proof of process plus much more — helping clients’ proof of process.

Dennis Beauchesne: Absolutely. That’s a big part of convincing people that this process is for them and that it works on their part. We can send them ten different reports of an exact same material and part, but they want to know what their part will do.

What is Modular Heat Treating? (02:50)

Doug Glenn: On a very basic, rudimentary level, what is modular heat treating and how does it differ from what might be considered standard or normal heat treating?

Dennis Beauchesne: A modular heat treat system is one that works together to have more than one furnace working in the same platform. You may have a shop that has five or six vacuum furnaces separated — they each have their own door, vacuum system, electrical supply, quench motors…those types of components. Or you may have a series of batch IQ furnaces for carburizing; those systems are one off, which means they are individual, independent systems.

In a modular system, you try to utilize those facilities for the use of multiple heating chambers. Instead of having one vacuum furnace with one set of pumps and one gas quench motor, what we would do is have three to eight heating cells that would be utilizing one quench, depending on the process timing; that’s all done with an internal transfer car and we try to utilize one vacuum system. It’s much smaller than what you would have for three, four, or even eight cells.

If you had oil or high pressure gas quenching, which is what’s dominating right now in the modular heat treat business, you could supply basically six batch IQ hot zones to one oil quench.

The savings then are huge simply by removing five or six other quench tanks in front of this system, as well as leveraging the floor space (and the number of pits you have to dig). Other advantages including utility savings and utilizing equipment across a number of heating chambers.

Doug Glenn: This modular approach is basically separate chambers that are dedicated to doing whatever that chamber is doing, and they are all in some way interconnected. For standard units, you would heat up, pre-process, do the actual process itself, cool down, all in the same chamber. In a modular unit, you move from chamber to chamber to do each of those separate steps.

Dennis Beauchesne: Yes, I refer to it as a continuous batch.

Doug Glenn: Continuous batch. We were talking before we actually hit the record button with your colleague there, Allison DeAngelo, who just got done visiting the Heat Treat Boot Camp. We were talking about different types of furnaces, and we started talking about continuous vacuum, which of course, is almost a misnomer — a vacuum can’t be continuous because you have to open it up and break the vacuum to get stuff out. Anyhow, we talked about it basically being a batch, right? A batch furnace that’s continuous, a continuous batch furnace.

Benefits of Modular Heat Treating (06:35)

Now that we have a basic understanding of what these modular systems are, why would companies want to move from the standard type of heat treating system to a modular system?

Dennis Beauchesne: Manpower. If you are running five or six vacuum furnaces, you are going to need a number of people to open the doors, put new loads in, those kinds of tasks. With a modular system, you only have one entry or one exit area. Therefore, you are only going to load once every 15-20 minutes, and the system is going to take over and control that load going through the system.

In addition, especially in a carburizing atmosphere situation, you can have every load be a different case depth — a different process in each cell — and then the next load that goes in that same cell can be totally different from the one before. For instance, if you had a batch IQ, you typically use the same carbon potential, and you are typically going to run the next load almost identical to the one before. In contrast, with the modular system, each cell can run a different process every load.

It’s also easier to integrate automation if you are doing capacity increases.

Throughput Comparison (08:00)

Doug Glenn: What is the comparison of throughput between a standard unit and a modular unit?

Dennis Beauchesne: The throughput comparison is interesting because you typically can use a little higher temperature for a carburizing and a little higher carbon potential, and of course that’s what we specialize in here with the modular systems. You can achieve about a 30-40% gain in your cycle time. That furnace is operating very close to 100% occupancy, because when that load is done, you are moving it out right into the gas quench. Then, the next load comes and goes right into it.

Doug Glenn: You are able to increase your throughput because you have basically 100% utilization of the equipment or very close to that. Comparatively, you don’t necessarily have that in the standard equipment.

Product Quality Comparison (09:15)

Doug Glenn: Do modular systems produce higher quality products?

Dennis Beauchesne: The quality of the parts coming out of the system is improved. A vacuum environment is a very clean environment, especially if we are considering atmosphere and low pressure carburizing — it’s in a vacuum. We typically do everything in high pressure gas quenching. However, even in oil quenching under vacuum, you are going to have a much cleaner part.

Also in low pressure carburizing, the carburizing is much more uniform throughout the part because we heat it to temperature under nitrogen before the part gets to austenitizing temperature to start attracting carbon. We make sure that the full part, that’s the tooth, the root, every piece of the part, is at temperature before we start adding carbon to the load, which makes a more uniform case depth, and therefore makes a stronger part.

Doug Glenn: Since each module, each chamber, is dedicated to doing what it is supposed to do, it seems like the consistency and the reliability of the parts being processed in a modular system have a much better chance of being higher quality.

Dennis Beauchesne: You do not have six different variable chambers or six different variable systems. You just have to look at monitoring the connection between those and understanding that the vacuum levels are all the same across the levels and across the cells. Each cell can meet a different temperature and run a different process, but those are consistent across the board.

Typical Dedicated Cells/Chambers (11:10)

Doug Glenn: What would be the typical dedicated cells/chambers of a modular system?

Dennis Beauchesne: It is dependent on the processes. They are most widely used for vacuum carburizing. For pre-oxidation and preheating, we usually use an air oven outside of the system, and we connect that with an external loader. Before the load goes into the modular system, the load will go through a regular air oven, be heated to around 700°F (400°C), and then the load will be moved in.

For sintering and those kinds of applications, there is a debind step or a preheat step that would be done in one cell. Some of the processes that can be done in a modular system include:

Low pressure carburizing
Low pressure carbon nitriding (LPC)
FNC (ferritic nitrocarburizing)
Nitriding
Debinding
Sintering
Neutral hardening

The most prominent process right now is LPC, and that is being used all over the world in these systems.

Advantages of a Modular Unit for Captive Heat Treaters (12:53)

Doug Glenn: Why would a modular unit be beneficial for a captive heat treater, someone who does their own in-house heat treating, which probably means they’ve got potentially high volume, low variability as far as their workloads?

Dennis Beauchesne: The modular unit has many different advantages. First of all, floor space. You are going to save a lot of floor space by not having multiple furnaces set up separately. You will also save utilities because you would not have as many vacuum pumps or electrical systems running these furnaces on their own. You will have some shared service and utilities in that fashion.

Doug Glenn: That would also likely lead to maintenance cost savings as well, correct?

Dennis Beauchesne: Yes, it all goes down the line. Anything that you have multiples of, you are going to have much less costs than on a joint system. The modular system might be a little larger than one singular unit, but there will be fewer of them.

For vacuum carburizing applications in a captive shop, the quality and cleanliness of the part is very, very important. Gas quenching lends itself to no oil in your plant, no washers necessary for a post-quench. Typically, there’s a washer before the process starts, but you do not have to have any wash to get the oil off of the parts with a modular unit — you do not have to reclaim the oil or the water from the washer. You would not have waste oil in your plant either or any oil on your plant floor. These are some of the reasons some of the larger captive shops have gone to the modular systems.

Also, safety: There are no open flames with a modular unit, no risks of fire on the systems. They are also easier to maintain. For a fully operational, let’s say, eight-cell system for high production, captive operation, it would only take about five hours to cool that whole system down if you had to go in and work on the whole system. In comparison, it’s going to take you three to four days sometimes to cool down a typical atmosphere, high-temperature furnace.

It also takes time to heat the system up again. In a modular system, it takes about an hour and a half to heat the system up again and then you are ready to start running. That means now you can schedule your downtime on weekends or holidays. You do not have to have staff present to run anything.

You also do not have to have a secondary equipment, like Endo generators running to feed the carburizing gas. The carburizing gas is using acetylene out of cylinders, it’s not a regenerative system. You do not need a separate piece of equipment to feed to the furnace.

Another benefit is CapEx expansion. Typically, captive heat treaters do not want to buy everything upfront because their volumes are going to increase over time. In the beginning, they typically only need one or two cells ready to do a small amount of production so they can prove out the production and prove out the system. Then they can start building the system with more cells and more capacity later on. Generally, it’s two to three days of downtime to add a cell to a system. It’s very convenient to do that with a modular system. All of the utilities are typically alongside the modular system so that you can easily add those or add a cell to it over a short period of time, and those cells can be ordered a year or two down the road whenever you might need that.

You also can order peripheral equipment, like extra temper ovens or additional automation. You can add a robotics system to the layout as well. That’s why captive shops are very interested.

Finally, workforce: It’s a little bit easier to get someone to work on a modular system. These systems are completely clean and white. The one located in our Synergy Center has been there for eight years. We use it every single day, and it’s a very clean aesthetic environment for someone to work in. These systems are also water cooled, which means not a lot of extra heat in the building around you to work in.

Advantages of a Modular Unit for Commercial Heat Treaters (17:59)

Doug Glenn: What are some advantages of modular units for commercial heat treating?

Dennis Beauchesne: On the commercial heat treat side, modular units are typically useful because you can get multiple processes out of similar cells and you can have a system that has oil and a gas quench.

You can have a lot of flexibility in that one system that you have in the plant. I’ve visited hundreds of captive and commercial heat treaters. They generally have a number of furnaces in one area of the plant, and a number of furnaces in another area of the plant. A modular system gives you all the capability in one machine and one tool: oil quenching, gas quenching, FNC, nitriding low pressure, carburizing, carbonitriding, and neutral hardening all in one piece of equipment.

Automation and Robotics with Modular Heat Treating (18:57)

Doug Glenn: What automation and robotics advantages are there with modular systems?

Dennis Beauchesne: This is the new trend. People that have modular systems are now considering, “How do I automate the system to get more production out of it?” And what we’ve been doing the last five years especially is implementing systems that use CFC fixtures.

CFC fixtures are very robust in the furnace but sensitive to being controlled outside. Therefore, what we try to do is have the CFC fixtures be utilized in an automation that no humans have to interact with it. We usually use robots for external loaders and internal loaders to move the fixtures through the process.

This causes you to have a lighter load, which means less heating time, less energy being consumed. Also, the fixtures last three to four times longer if they’re not damaged. But of course, all of these systems can be using regular alloy steel as well, and we can fixture different parts. You can use baskets, we are now doing bulk loading where we have parts that are filled into baskets and then processed. We are doing that with vacuum carbonizing as well, not just neutral hardening.

So it’s really interesting to see how the limits are being pushed, as well as the different materials that we are gas quenching now. I know 20-25 years ago, we were quenching some simple materials that were very high hardenability, and today we’re quenching a lot of less hardenability steels.

Doug Glenn: Is that primarily due to increase of pressure in the quench?

Dennis Beauchesne: It’s pressure, it’s flow, it’s the intensity of the gas going through the parts. It’s also heat removal as well — heat exchangers, removing the heat out of the load faster. We also have reversing gas quench motors to reverse the flow inside from top to bottom, bottom to top, in the middle of the cycle.

Sustainability of Modular Heat Treating (22:24)

Doug Glenn: Do these systems promote sustainability and greenness?

Dennis Beauchesne: Absolutely, especially when it comes to carburizing. These systems have been compared against typical atmosphere carburizing cycles, and only about 4% of the carburizing time has gas injection, when we are actually injecting acetylene and having hydrocarbons being used in the process.

If you took the same cycle times, seven or eight hours of a carburizing cycle, you are flowing Endo gas or nitrogen methanol in the system for that full time. In contrast in a vacuum carburizing system, it’s 4-5% of the time of the cycle that you’re injecting into the furnace. Ultimately, you only have about 10% of the CO₂ output that you would have in a typical atmosphere furnace.

As mentioned previously, there’s also no oil in your plant. You’re not reclaiming oil out of the water and the wash or off the floor or in your car when you leave your heat treat shop.

How Does the Modular Heat Treating System Work? (23:40)

Doug Glenn: Let’s talk through the process a little bit. You provided us with figures to aid in describing the process. We have included these. Describe how the system works.

Dennis Beauchesne: This animation is a plan view of one of our Flex systems. In the center, going left to right, is a tunnel section. This tunnel section is about an 8-foot diameter. It has an automated loader that moves down left to right or horizontally, and it transfers loads from each cell to another, in and out.

On the bottom left is a loading/unloading chamber. In that loading/unloading chamber, we remove the air once the load is put in there, and then we balance the vacuum on that cell to the tunnel’s vacuum. Then we’re capable of moving that load to an available heating cell, and that would be on the right of the system — on the top right or the bottom right of the tunnel, those are heating cells. Then recipe for that particular load will be loaded into that cell. While that load is processing, another load will be moving into the tunnel and into the other heating cell as well.

On the top left is the gas quench cell, which could be in this orientation or instead have an exit on the back as well. In this system, you could do neutral hardening, carbon nitriding, LPC, a number of the processes. This is a very valuable tool, especially in a commercial heat treat heat treat shop.

Doug Glenn: Is this whole unit, including all four chambers under vacuum? I noted there are separation doors on the purge and the entry chamber. Can this area be vacuum sealed?

Dennis Beauchesne: Yes. There are vacuum seals on the loading/unloading chamber on the bottom left and then the top left. The gas quench also has a seal from a pressure standpoint. The two heating chambers have a graphite door — we call it the flap door, and it just flaps and it doesn’t really seal actually against another face of graphite. It’s graphite-to-graphite. We pull vacuum out of there through the tunnel to create the central vacuum pressure in the system. We also pull vacuum from the cell itself, and we could also have a separate door on the front of the unit if the process necessitates that or if we feel that a door is needed there by a client.

In a normal state or a standard unit, there are no hot seals on the door, only vacuum seals on the loading/unloading chamber and the gas quench.

Doug Glenn: In the animation, your vacuum pumps are down in the bottom right, correct?

Dennis Beauchesne: Exactly, that’s a process pump.

Doug Glenn: What is located in the top left?

Dennis Beauchesne: On the top left, we have a gas quench tank. We want to ensure we have enough gas pressure and volume there to quench the load quickly. It’s very important to get the gas through the gas quench quickly.

ECM Flex 600TG vacuum furnace with two added heating cells / Source: ECM USA

Now, we have added two more additional heating cells and a central tunnel section. In essence, you just doubled the space, doubled the capacity of the unit, where you only added 50% of the space of what you had for capacity before.

We are still utilizing the same gas quench and the same loading/unloading cell. We only added utilities for the two heating cells, not for a whole gas quench or oil quench capability there; this can be added in a very short time.

Doug Glenn: Now I’m gonna go let this video roll here for a minute. There we go.

**ECM Flex 600TG vacuum furnace with four added heating cells for six heating cells total**

Dennis Beauchesne: So now we added another 50% capacity with two more heating cells (six heating cells total) and a tunnel section. Typically, what you want to do is to have the tunnel sized for about five years out for your capacity and then buy the cells as you need them and have it grow so then the tunnel is ready to implement.

We have just tripled the capacity of this installation, and we are only still using the same gas quench and the same loading/unloading cell. Generally, this system could go to eight cells and have just one gas quench, that’s our typical orientation.

Doug Glenn: It looks like we also added a discharge side here. Whereas before we were going in and out.

Dennis Beauchesne: Yes, this adds to the efficiency of the system because the load is already in the gas quench when it’s finishing, so it just exits out the back, out the door.

Doug Glenn: Now what do we have here?

**ECM Flex 600TG vacuum furnace processing different treatments in each cell. See animation above to watch the animation in motion.**

Dennis Beauchesne: We have the loads entering, and the loads will go to the first cell that is available (empty). Then that recipe would be downloaded for that cell, and then the next load will go to the next available heating cell and download that recipe into that cell. These could be two different loads.

One load could be for neutral hardening; one could be for carburizing. One could be for carburizing in a low case depth. The other one could be carburizing at a deeper case. In this case, we just see the gas quench on here, but this tunnel could also be outfitted with an oil quench as well, and you could have one load go into gas, quench one load, go into oil quench or both going to either.

Doug Glenn: This gives people a sense of what the process looks like.

Processes and Materials for the Modular System (30:29)

Doug Glenn: Are there any processes or materials that do not make sense to process them through one of these systems?

Dennis Beauchesne: If you are doing a lot of annealing and normalizing, those are longer cycles. There is some regulated cooling that occurs. This is not really the type of equipment investment that you would want to make for those processes. If you were going to use it for a few loads in your plant where you received parts that weren’t annealed or you wanted to try to anneal a part for a particular process before you went to full production, you could certainly use a modular system for that, but it’s not a cost effective methodology. Neither would we recommend preheating in the cell. However, it is very flexible for a number of other processes that we have mentioned.

The size of the part is also important to note. These systems are typically 24 inches wide and about 39 inches long and about 28 inches high. However, we will soon have a new system, the Flex Max, a 12-9-9 system. It’s a 36×48 unit that comes with an oil quench and is modular, like this. We can either do an oil quench or a slow cool cell on that system. So, we will have that capability of 36×48 in that modular system.

Other than that, restrictions on material? Very few there. Like I said, you would not want to do annealing and normalizing on a lot of parts, but you could do it in these units.

Doug Glenn: It sounds like the sweet spot is surface modification type applications, and some sintering is possible with dedicated chambers.

Dennis Beauchesne: Yes, sintering and brazing is also possible.

Doug Glenn: Does that include aluminum brazing?

Dennis Beauchesne: Not aluminum brazing, but some brazing applications.

Expenses with Modular Heat Treating Systems (33:03)

Doug Glenn: What would be considered capital expenses for this modular system?

Dennis Beauchesne: As far as capital expenses, it’s not a furnace-to-furnace comparison. Clients always ask how much our furnace is. But companies need to first take two steps back and take a look at their incoming material, how they would like to be able to modify that incoming material in their heat treat process to make sure that their outgoing quality is higher than it is today. That’s the kind of benefit that this type of modular system gives you — a better quality part, safety in your plant, and a better quality work environment with being able to turn the system off and not need additional personnel around.

These are all factors that have to be considered when thinking about the CapEx expenditure and investment. When we consider these factors, a modular system investment is a much better situation than looking at a furnace-to-furnace replacement, and that’s really the thought process that clients need to go through to understand the actual investment and value of the system.

Doug Glenn: What about the operational expenses?

Dennis Beauchesne: For instances, if you had a batch IQ sitting there, you would typically keep it running whether it has a load in it or not. With a modular system, you just shut off that cell that you’re not using. It does not take any more energy. If you are not working five days a week, you do not use it on the weekends — you shut it off. You do not use it during Christmas shutdown or any holiday shutdown, vacation shutdown. You’re able to shut it off and that means saving a lot of energy and labor by having it off.

Also, in the opposite way, you could run it lights out if you wanted, as well. You could stock up a number of loads on the automation before you leave, have the system operate it, run it, and have the load come back out before the morning. You could have it time start as well, if you wanted to start it on Monday at 5 AM, but you will not be there till 8 AM. You would come in and the furnace would be hot and ready to run a process.

There are a number of operational advances over the typical operational heat treat that’s out there today.

Doug Glenn: How does maintenance work with these systems? Say your heating element goes bad in cell number three, do I have to shut the whole system down to fix or can I fix number three and leave the rest of the system up and running?

Dennis Beauchesne: In this situation if you had a tunnel like we showed, you would typically shut off that cell; that is, if you knew that heating element was out or it wasn’t heating properly, you could shut off that cell, de-validate is what we call it, and then keep running the rest of the system until you had a window in your production that you could shut the whole system to get into that heating element.

If you had a system with doors on the front, it could be possible to go in the back while the system is operating. Then, it would be all based on your safety requirements for your plant and those kinds of things.

To do that, we have another system called the Jumbo, and it is much more flexible in the maintenance world. It has a vacuum car that moves down on rails and docks and mates with every heating cell on the system. In that line, the heating cell can actually be isolated from the rest of the line. You would just slide it back (It’s on wheels, it slides back about three feet away from the line), you put in a new piece of safety fence, and you continue to run your line. You can completely lock out/tag out that cell and work on it completely.

Doug Glenn: How would you approach a vacuum leak since the whole system is connected, right? I believe you mentioned these are graphite-on-graphite doors.

Dennis Beauchesne: You would want to fix the leak before you move on. Especially if it’s a bad leak. If it’s something that’s causing you to not maintain your process pressure, you certainly don’t want to do that, and that’s true with every vacuum piece of equipment.

ECM Modular Systems (38:55)

Doug Glenn: How many of these modular type systems does ECM have out in the marketplace?

Dennis Beauchesne: The Flex is the most popular modular system, which we discussed with the animation. We also have a number of Jumbos systems, and the unit in our Synergy Center is called a Nano, which has become more and more popular these days. The Nano has three different size chambers, but they’re typically smaller, 20x24x10 inch high size chamber. I explained a little bit about the Flex and the Jumbo is the same.

Out of those three systems, we have more than 350 modular systems, not just the heating cells, but more than 350 systems that are out in the marketplace today operating, running parts every day, running millions and millions of parts every week. Those systems are comprised of about 2,000 heating cells. As much as people hear about this being a new technology, it has actually been around about 30 years, and many companies have been using these systems and have replaced a number of pusher furnaces and those style furnaces for high-capacity installations especially.

Doug Glenn: Okay, that sounds good. I really appreciate your time.

About the Guest

Dennis Beauchesne
General Manager
ECM USA

Dennis Beauchesne joined ECM over 25 years ago and has since amassed extensive vacuum furnace technology experience with over 200 vacuum carburizing cells installed on high pressure gas quenching and oil quenching installations. Within the last 10 years, his expertise has expanded to include robotics and advanced automation with the heat treat industry high-demand for complete furnace system solutions. As General Manager of ECM USA, Dennis oversees customer supply, operations and metallurgical support for Canada, U.S., and Mexico for ECM Technologies. He has worked in the thermal transfer equipment supply industry for over 30 years.

For more information: Contact Dennis at DennisBeauchesne@ECM-USA.com.

Find heat treating products and services when you search on Heat Treat Buyers Guide.Com

Heat Treat Radio #127: The Case for Modular Vacuum Heat Treating Read More »

5 Things To Consider When Choosing a Refractory Lining

November 17, 2025 / Manufacturing Heat Treat Technical Content, VACUUM FURNACES TECHNICAL CONTENT

For heat treaters, choosing the right refractory lining is critical to keeping furnaces running safely and efficiently. Linings must endure extreme heat, stress, and chemical attack while balancing downtime, longevity, and cost. In this article, Plibrico Company Technical Services Group explains how refractory engineers carefully balance five critical factors to deliver solutions that meet today’s demanding production needs.

In refractory lining maintenance, recommendations for repairs and relines often consist of selecting a similar or equivalent material to replace the original. Sometimes that’s sufficient. Many refractory contractors and maintenance teams strive to use best practices by purchasing the same refractories that have worked on similar equipment in the past, but this carries the risk of assuming that nothing has changed in the process, production, or maintenance of the equipment over time. This assumption can be a dangerous bet because furnace equipment is made to meet the immediate demands of each thermal processor, and these demands often change depending on factors like production orders and maintenance capacities.

Choosing an appropriate refractory lining for an application isn’t always a straightforward decision. Many times, it is part science and part art. Making an effective choice requires knowledge of the industrial application process, refractory performance expectations, and potential refractory service failures. These factors must then be weighed against each other to find the right balance and best solution.

While there are a number of important criteria to consider, refractory engineers focus on five aspects to evaluate and choose a refractory material for each specific application: thermal, mechanical, chemical, logistics, and value — as well as connections among these aspects.

What is the best refractory material choice? To answer this question, each individual application requires an overall evaluation of the thermal processing furnace in relation to each of the five factors, and then a careful balance of each of these in finding the best solution that meets both the immediate and long-term needs of the thermal process.

Thermal Requirements: Temperature

For any high-temperature industrial process, the primary piece of information is the operating and maximum temperatures. The refractory lining chosen must meet the operating temperature requirements.

Refractory linings are designed to maintain physical properties at very high temperatures — 932°F and above. Refractories used to line thermal equipment must have proper insulating properties to reduce the steel skin temperatures to acceptable levels, usually well below 300°F. Multi-component linings employ a dense refractory material at the hot face with an insulating refractory or ceramic-fiber board or blanket behind it, well-known for achieving adequate cold-face temperatures with structural integrity for long thermal life.

Spalling and thermal shock are the most common thermal failure mechanisms in a refractory lining. These are due to crack formations caused by temperature cycling and high thermal loads. There’s more to learn about fracture mechanics thanks to expert research, but knowing the importance of this phenomenon is enough for the application specialist.

Refractory engineers working on refractory layer
Source: Plibrico

In recent years, many thermal processors have experienced increased production demands. Meeting that need means that their furnaces are operating at higher temperatures for increased output. Running furnaces harder and faster often has the unintended consequence of overheating the refractory to the point that phase changes in the refractory matrix start to occur, causing lower-temperature glassy phases to form, softening the refractory, and shortening life. Due to this, the refractory engineer often needs to consider a material with higher refractoriness to meet the performance needs of shock resistance and high thermal loading. This usually means a higher-alumina material.

Physical Properties: Mechanical

The vast majority of higher-performing refractories in service today have been developed to maximize a material’s physical properties to improve lining lifespan and keep furnaces running at their best performance. Much of the information on a product Technical Data Sheet is devoted to the physical properties of the material, such as cold crushing strength, hot/cold MOR, and abrasion resistance. All of these are based on well-defined ASTM standards to make valid comparisons among available choices.

Refractory linings experience all sorts of mechanical and thermal loads that lead to wear and eventual failure, requiring repair or replacement. Some of these include excessive expansion, thermal cycling fatigue, mechanical impact (dynamic loading), severe abrasion and erosion, pinch spalling, tensile loads, large hydraulic loads (such as in molten-metal containment furnaces), and creep (deformation at high temperatures over time). While a deeper discussion of each of these failure modes is beyond the scope of this article, knowing the type of potential refractory failures for each application becomes the solution in choosing the refractory to best address the failure mode present.

During a visual refractory inspection, the lining can often give clues about failures. Crack patterns, wall buckles, surface spalls, discolorations, and other visual differences occur in locations and manners that correspond with their failure type. Mechanical and thermal forces will find weak points and initiate cracking. Many times, these occur in typical geometric locations and patterns, such as sharp inside corners, archways, midpoints of a lining, and in circular patterns, indicating a particular failure system. These will usually indicate shock and expansion due to high thermal loads, inadequate expansion allowance, deficient material properties for the application, and/or improper anchoring.

Corrosion: Chemical

Chemical attacks on the refractory matrix have been a fundamental concern of ceramics engineers since the beginning of refractory development. Chemical reactions between the vessel’s contents and the refractory at high temperatures can cause a change in the structure of the refractory matrix, which can have a detrimental effect on the performance and life of the lining. Chemical or mineralogical changes due to reactions occurring within the refractory lining can cause excessive volume change of the crystal structure or reduction of the oxides in the lining, leading to a breakdown of the ceramic bonds in the cement. The most common examples of these are:

A reducing atmosphere of carbon monoxide reacting with the lining, such as in CO boilers

An H₂ reaction in the lining, which reduces silica in the refractory matrix at high temperatures

Molten slags, such as in coal-fired boilers

Alkali corrosion from ash in wood-burning furnace applications

Corundum growth in aluminum furnaces, especially those with aggressive alloys containing MgO

Installation: Logistics

In addition to the aforementioned elements, refractory construction contractors are faced with multiple logistical pressures to get their clients’ thermal processing equipment back on-line. This means that the choice of anchoring systems, installation methods, and bake-out becomes an important consideration.

The adage “time is money” is often a deciding influence when crafting a refractory solution. “Get it back up and running ASAP” is often the most pressing need communicated by the thermal processor. For example, while a brick lining often gives clients a highly durable option, bricking a job is very labor-intensive, requires high levels of experience, and usually takes a long time to complete. A cast-in-place lining may yield the best physical properties in service, but the time also needed for forming (or multiple formings), casting/pumping, then stripping may not be desirable. In other words, the required length of downtime may not justify these options.

Another example is the use of low-cement castables, which have superior properties. These have been around since the Plibrico Company first developed them, but they require more careful and longer bake-out. Gunning or shotcreting the lining could be a viable option if time or cost is a determining factor because forming is not required, and material can be placed at higher rates.

While a cast product theoretically produces the best physical properties in general, followed by shotcrete and gun mixes, time limits may require another method of installation. Other factors to consider may be to ram the lining using plastic, which requires no setting or moist cure requirements. With the advent of reduced bake-out refractories, such as Plibrico’s Fast Track castables and gun mixes, contractors can place material and fire several hours sooner. This saves time and money but often at a cost of reduced physical properties. Again, it is a balancing act.

Price: Value

Refractory linings are one of the most significant operational costs over the life of an industrial furnace. Therefore, when choosing a material for the application, price is always a very important factor. However, value is not only reducible to price; there is often more than one choice of materials to pick from.

The economics of each individual application can direct the engineer/specialist to recommend one solution over another. When we speak of price, the real driver is value. Everyone wants a refractory product installed that is good, fast, and inexpensive. However, it is often very difficult to achieve all three of these simultaneously. Value is the determination of the relative importance of each.

Conclusion

The question to be asked is this: What do refractory linings do? Their most basic function is to withstand very high temperatures; contain heat within a vessel; have adequate physical properties, such as strength; and resist chemical degradation or disintegration by aggressive atmospheres and corrosion by liquid slags and solids.

Choosing the right material solution for thermal processing applications requires balancing multiple aspects to determine a hierarchy of which aspect is most important. In many cases, there is no single answer to the problem. However, understanding the process, challenges, history, and root causes of refractory failures becomes the key to making the best decision to solve the problem.

For more information: For more information about choosing the best refractory lining, contact Plibrico Company at contact@plibrico.com or 312-337-9000

This informative piece was initially published in Industrial Heating. All content here presented is original from the author.

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Customize To Build Better Furnaces

November 11, 2025 / AEROSPACE HEAT TREAT TECHNICAL CONTENT, AUTOMOTIVE HEAT TREAT TECHNICAL CONTENT, VACUUM FURNACES TECHNICAL CONTENT

Custom furnace design isn’t just about performance upgrades — it’s about process reliability. Vacuum furnaces built for general use, however, often fall short in high-precision industries. This Technical Tuesday installment comes to us from Scott Herzing, vice president of Engineering at Paulo. Explore how purposeful furnace design, smarter controls, and targeted customization can transform vacuum heat treatment.

This informative piece was first released in Heat Treat Today’s November 2025 Annual Vacuum Heat Treating print edition.

The reliability and consistency of vacuum heat treatment processes depend heavily on furnace design and performance. Standard furnace configurations typically serve general heat treating applications adequately. However, for industries with extremely demanding requirements, such as aerospace, automotive, and power generation, small variations in furnace design can lead to substantial impacts on part quality, increasing risks and costs. Achieving exceptional process control and repeatability often requires custom furnace modifications tailored specifically to the unique requirements of each process.

Extensive customization of vacuum furnaces can initially seem costly and complex. It takes experience operating and refining vacuum furnaces to know which adjustments deliver the greatest impact. This article taps into the more than fifty years of heat treating wisdom from Paulo with six key factors that drive better furnace performance, enhance reliability, reduce downtime, and create measurable efficiency gains.

Why Customization Matters

Conventional vacuum furnace models offered by manufacturers are generally designed to meet broad market demands. This often results in equipment that effectively balances functionality, affordability, and ease of use for a wide range of applications. However, certain high-precision thermal processing applications, especially those involving aerospace components like single-crystal turbine blades demand much stricter temperature uniformity, controlled quenching rates, and near-perfect repeatability from cycle to cycle.

In these cases, standard configurations can introduce variability that compromises quality. A better path is a case-by-case approach, evaluating specific process risks and targets critical components for modification. Precision upgrades can be integrated where they have the greatest impact, achieving the required level of process control. This makes it possible to achieve near-zero scrap rates, dramatically boost reliability, and achieve repeatability that far exceeds industry norms.

Advanced Pressure and Cooling Control

Repeatable quench dynamics is a game-changer when it comes to part quality. Integrating advanced gas control capabilities that extend beyond basic pressure management can help you improve heat treating results. To do this, you need to precisely control the rate at which gas is introduced into the vessel using proportioning valves, not just the pressure setpoint. For controlled cooling cycles, systems also need to manage the fan start speed, allowing you to tailor the convective heat transfer to the geometry and mass of each part. This level of precision ensures consistent metallurgical results and protects part integrity.

Automation-Ready Resilience

In multi-furnace environments that rely on automation and minimal staffing, power-failure restart behavior cannot be left to chance. Adding dedicated PLC logic for restart allows the system to record the exact state at interruption, verify safe conditions on recovery (atmosphere, temperature, motion, interlocks), and automatically sequence a safe restart when criteria are met. This reduces scrap risk, protects equipment, and stabilizes throughput, especially when only a few operators are covering many furnaces.

Hot Zone Design and Material Selection

A major component directly influencing furnace reliability and overall performance is the hot zone. As the central area where thermal processing occurs, the hot zone repeatedly experiences extreme temperature fluctuations, making its design crucial to operational efficiency and product quality.

Standard vacuum furnaces use thinner insulation layers and lower-cost materials to control initial investment costs. However, advanced hot zones can dramatically outperform these standards by incorporating thicker insulation layers, strategically placed air gaps, and specialized insulation materials, such as high-quality molybdenum, graphite felt, or carbon-fiber-carbon (CFC) boards.

These advanced materials not only prolong hot zone life but also substantially reduce heat loss, minimizing energy consumption and improving thermal uniformity. The enhanced durability also results in fewer service interruptions, less downtime, and lower long-term maintenance costs, ultimately justifying the higher initial investment. At Paulo, this is how we’re able to reliably run around 29,000 cycles per year in over thirty furnaces at our Cleveland facility.

Additionally, the hot zone’s construction details, including how insulation and heating elements are attached, can significantly affect longevity and reliability. Standard fasteners or attachment mechanisms may perform well in general applications but frequently deteriorate under high-stress thermal cycling. High-performance fasteners specifically engineered for high-temperature stability reduce the risk of premature failure and minimize downtime.

Enhanced Sensor Integration

Furnace reliability and consistency rely heavily on the accuracy, quantity, and strategic placement of sensors within the furnace chamber. Manufacturers’ vacuum furnace designs typically include a limited number of sensors monitoring basic parameters, such as temperature, pressure, and vacuum levels. Increasing the number and distribution of sensors throughout the furnace interior allows for a more detailed and accurate understanding of conditions during processing. By placing multiple sensors at critical points within the hot zone and throughout key furnace components, operators can detect subtle differences in temperature distribution, heat flow, gas pressures, and quench rates that might otherwise go unnoticed. This enhanced sensor density provides the detailed data necessary for real-time process adjustments, early detection of equipment issues, and predictive maintenance interventions, significantly improving process reliability and part consistency.

In addition, the rich data captured by a denser sensor network improves traceability and enables rapid identification of root causes when process deviations occur, ultimately reducing the risk of quality issues and equipment downtime.

Centralizing Your Control System

One often-overlooked factor in achieving highly consistent heat treating results is the adaptability and responsiveness of furnace control systems. Modern furnace control architectures benefit from a centralized SCADA layer with deep PLC integration. By recording every PLC input (thermocouples, switches, interlocks, drives, flows, pressures), the system enables technicians to diagnose issues without walking out to the furnace and manually testing components. With complete signal histories available, furnace issues can often be diagnosed and resolved remotely in minutes, improving first-pass resolution and minimizing production disruption.

Integrated control software should do more than log data; it should actively protect quality:

Automated compliance control: Continuously track process parameters, alarm on deviations, and initiate quality quarantines when limits are exceeded to prevent suspect parts from re-entering the supply chain.
Element-health monitoring: Monitor heating-element resistance to detect early signs of a heating system issue. If an anomaly is detected, automatically stop the heating process to protect parts and prevent secondary furnace damage.

These safeguards shift intervention upstream and reduce reliance on manual inspection alone.

Extending Auxiliary Equipment Life with VFDs

Variable-frequency drives (VFDs) on pumping systems can substantially extend motor and bearing life by matching speed to process demand and reducing mechanical stress. When control logic conditions are met, slowing pumps lowers load, heat, and vibration, which are key contributors to premature failures.

Without VFDs: Bearings on 615 blowers typically require replacement every 1–2 years, and motor failures occur more frequently than acceptable.
With VFDs + logic-based speed reduction: Bearing-change intervals extend to 10–20 years, with no motor problems, reflecting a step-change in reliability and lifecycle cost.

This targeted upgrade is a practical, high-ROI improvement that also helps decrease unplanned downtime.

Practical Realities and Final Considerations

Extensive furnace customization offers clear advantages, but it is not always practical for every operation or budget. In many cases, targeted, incremental upgrades — such as refining hot-zone insulation and attachment methods, adding or repositioning select sensors, or phasing in improved control software and deeper data storage/analysis — deliver measurable gains in reliability and process quality without large upfront costs.

Another practical path is to partner with a commercial heat treater that has already engineered and validated these enhancements at an industrial scale. This option can accelerate access to higher levels of precision and repeatability without requiring capital investment, engineering bandwidth, and learning curve of doing it all in-house.

Ultimately, achieving reliable and repeatable heat treatment results involves careful consideration of furnace design and functionality, aligned closely with your process requirements and economic realities. While extensively customized furnaces represent the ideal for particularly demanding applications, understanding the targeted areas where smaller customizations can yield significant improvements empowers heat treaters across the industry.

About The Author:

Scott Herzing
Vice President of Engineering
Paulo

Scott Herzing is vice president of Engineering at Paulo. He leads the company’s metallurgical, project and automation engineering, fabrication, and lean technology groups. With over 27 years at Paulo, Scott applies his passion for leadership, engineering, and problem-solving to help customers achieve advanced heat treating outcomes.

For more information: Contact Scott Herzing at sherzing@paulo.com.

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Heat Treat Radio #123: Helium Leak Detection Tips for Vacuum Furnace Operators

July 24, 2025 / HEAT TREAT RADIO, Manufacturing Heat Treat Technical Content, VACUUM FURNACES TECHNICAL CONTENT, VACUUM PUMPS GAUGES VALVES NEWS

Helium leak detection is critical to ensure system integrity, product quality, and operational efficiency in vacuum processing. With 36 years of hands-on experience, Dave Deiwert of Tracer Gas Technologies joins host Doug Glenn on the most recent episode of Heat Treat Radio to share a wealth of knowledge on the evolution of leak detection technology, practical maintenance, and best practices for leak testing.

Listeners will gain practical insights into the best leak detection practices and how to troubleshoot challenges.

Below, you can watch the video, listen to the podcast by clicking on the audio play button, or read an edited transcript.

HTT · Heat Treat Radio #123: Helium Leak Detection Tips for Vacuum Furnace Operators

The following transcript has been edited for your reading enjoyment.

Introduction

Doug Glenn: Helium leak detection has come a long way, but not everyone has a brand new piece of equipment. So let’s talk about some of the shortcomings of older equipment and some of the improvements that you’re seeing.

Dave Deiwert: When I started in 1989, leak detectors pretty much had what were called oil diffusion pumps as the high vacuum pump. That’s the pump that creates the vacuum for the analyzer cell or mass spectrometer so they can separate helium from other gases. These diffusion leak detectors did not like to be shut down improperly or have power outages quite frequently.

You would hear stories of somebody that turned the power off of a leak detector without a proper shutdown or a power outage, and that could cause an oily mess from the diffusion pump, and maybe even crack the oil. So, you would end up having quite a maintenance event required on the leak detector before you could use it again.

In fact, these kinds of problems happened so frequently that in my young sales days when turbopump leak detectors first were introduced, as I would go in to show it to a potential client, one of the first questions was, “What happens if you have a power outage?”

I would have a little fun with that.

I’d say, “Well, let’s find out.” And I would pull the plug out of the wall, and they would say, “Oh, you can do that?” And of course you could. A turbo pump would just coast down towards a stop. Then we turn the power back on, and it’s back up.

Part of what compounded this problem with the diffusion pump is that it works by heating oil to jet mist oil vapor that goes to the top, and it’s condensed and directed back down. When power is lost, whether you turn the power off with an improper shutdown or a power outage, that pump is still hot for quite a while. It’s still trying to pump, and the backing pump, whether it’s a diffusion pump or a turbopump, is typically a rotary vane pump. With a power outage or power stop, those pumps will come to a stop very quickly. But those diffusion pumps and turbo pumps are not designed to exhaust atmosphere, so the backing pump or rotary pump comes to a stop pretty quickly, and now you have atmosphere potential on the exhaust of the diffusion pump.

The turbopump survives that much more nicely than a diffusion pump does. So the first major upgrade in the technology across the board with all the manufacturers was moving away from diffusion pumps to turbo pumps. If you buy a new leak detector from the ‘90s to today, it will very likely have a turbo pump no matter whom you buy it from and even if you buy a used one.

Size and Portability of Leak Detectors (00:06:09) 

Doug Glenn: How large were these original pieces of equipment? Did you have to wheel them around?

Dave Deiwert: The very first ones I worked with predominantly would be the size of a washer/dryer. They would typically have casters on so you can roll them around.

Turbopump Leak Detector
Source: LDS Vacuum Shopper

They took up more space and certainly took up a lot more energy. You could sometimes find what they would call portable leak detectors, but they would still have diffusion pumps in them, and they’d have less features because of how small they were versus the console leak detectors.

Doug Glenn: So now nowadays they use helium leak detectors.

Dave Deiwert: Most everybody’s gotten away from console leak detectors. You can find a couple companies that have a fairly large rolls-on-caster leak detector that still has turbo pumps, and higher performing backing/ruffing pumps. But the majority of leak detectors you’re going to find are more portable and smaller in size.

Doug Glenn: Are they close in size to a briefcase?

Dave Deiwert: They average 12 to 18 inches wide by 10 to 12 inches deep and 12 to 14 inches tall, approximately. So, much smaller than a washer/dryer.

Quite frequently, these leak detectors may be sold with a cart so that you don’t have to carry them from point A to point B. It can be a little laborious to still carry them. They weigh 40 lbs or more. So quite often, the first accessory purchased with the leak detector is a cart to roll it around.

Doug Glenn: So it’s a heavy piece of carry-on luggage essentially.

Dave Deiwert: Absolutely.

Maintenance: Old vs. New Leak Detectors (00:06:37) 

Doug Glenn: How would you compare the maintenance of those older units, assuming that you don’t lose power, versus maintenance of the newer units.

Dave Deiwert: A stereotypical experience from my field service days would be if you’re running a diffusion pump leak detector in a production environment, using it every day, then most likely you’re going to do what I call an overhaul of the leak detector. During this overhaul, you’re going to change your oils, change the filaments in the mass spectrometer, put on new valve seats, and clean the manifold.

Not everybody will do this. There are those that might go a year or two, especially if the leak detector is purely for troubleshooting, like if you have only a few furnaces. The leak detector may sit against the wall, and then you go get out to leak test a furnace. They may well get a couple of years of use out of a leak detector before needing to do any preventative maintenance or even a major overhaul.

With the new turbopump leak detectors, I think all the manufacturers now have models that most likely you’ll go multiple years without really doing anything other than changing oil in the backing pump, which you might do a couple times a year or so, keep an eye on the oil level, much more maintenance friendly and easier to do the troubleshooting and the service to it.

Filament Technology Improvements (00:08:10) 

Dave Deiwert: The next major upgrade in the leak detectors across the industry was the filament design.

The old diffusion pump leak detectors predominantly had tungsten filaments, which, if you’ve ever cracked or seen a cracked light bulb that had a tungsten element in it, you know that immediately you lose the function of the light bulb. And the same thing with the filaments that are tungsten in a mass spectrometer. If it gets a pressure burst, which is what I call the event when somebody disconnects the test port from the vacuum furnace while the leak detector is still in test, that allows a pressure burst into the leak detector and tungsten filament, and most likely you will burn out the filament. As a result, you will have a maintenance event for that.

As a rule of thumb, you will get 1,000 to 2,000 hours out of an old leak detector with tungsten filaments, but you’re going to get many thousands of hours out of a Yttria coated-iridium, which I think is used across the board in the industry today. In the case of

several years even, it greatly reduces your cost of ownership with the newer leak detectors.

Performance and Cost Comparison (00:09:12) 

Doug Glenn: Are there any other major differences between the old units and the new units?

Dave Deiwert: There are some extra benefits from the upgrades that we’ve talked about. The turbopumps will allow, at least modern leak detectors, us to test at a higher pressure (or less vacuum). You press “Start Leak Detector.” The test port pressure pumps down to some vacuum level. For diffusion pump leak detectors, they had to get down to typically less than 50 mTorr. Depending on the model, definitely significantly lower vacuum than the turbopump leak detectors. So, the turbopump ones with the gross leak testing capabilities, you’re probably looking at 18 to 20 torr. I think a couple of manufacturers claim they can get in the test pretty much right below atmosphere and start looking for very massive leaks.

The capabilities going to turbopump and Yttria-coated filaments has allowed manufacturers to greatly improve the performance and the robustness and reliability of the leak detectors.

Doug Glenn: In terms of cost comparison, are newer units more or less expensive than older units?

Weighing the costs and comparisons of different units

Dave Deiwert: When buying a leak detector in 1889 to early ‘90s, you’re probably looking at the low to mid-20s in price. You’re going to find they are a little higher than that now. With the market and inflation, you’re probably looking at upper 20s to low 30s for the most typical leak detectors that are purchased for the vacuum furnace industry. You can find some that are maybe two or three times that amount, but those are not needed for the industries that we’re talking about today.

Troubleshooting and Service Efficiency (00:11:00) 

Dave Deiwert: If the client, their suppliers, or people who work on the leak detectors from time to time service a diffusion pump leak detector, they may want to explore an idea to troubleshoot a problem. They may not be sure what the problem is yet.

First, you’re going to do a proper shutdown of the diffusion pump leak detector to protect the oil in the diffusion pump and the cleanliness of the leak detector. You may wait a good part of an hour for that diffusion pump to cool off before you can try the troubleshooting solution you’re going to investigate. Then you’re going to wait for another good hour for it to heat back up and be ready to confirm if what you have tried to do was successful.

With a turbopump leak detector, you turn a switch off to turn the power off, and within minutes you can test out the solution on the leak detector. So you greatly expedite your troubleshooting time.

What might have been almost always a full day event of troubleshooting and servicing a diffusion leak detector turns into less than a half day, possibly even an hour or two.

In every category, the newer leak detectors are very attractive. If clients or our viewers reach out to their suppliers or potential suppliers, there will most likely be some trade-in value for your old leak detector, which will also help offset the pain and suffering of spending money on a new leak detector.

Doug Glenn: Hopefully they’ll come pick it up, too.

Where to Connect Leak Detectors on Furnaces (00:14:11) 

Doug Glenn: In your column, you talk about how there’s some debate amongst users on where to hook up the leak detector on the furnace. Can you walk us through that a bit?

Dave Deiwert: I run into people who are very adamant that you hook up the leak detector in one of three places. And I’ve told salespeople that while we have our preferred location of where to hook to the leak detector, we should never visit a client and tell them they are doing it all wrong. As a field service engineer, I’ve confirmed that you can connect the leak detector at three most prominent locations, but the question is where is the most optimum place to connect it?

The first place is hooking the leak detector directly up to the furnace chamber, because that’s where they imagine the leaks might be. The next two locations might look like close cousins because they’re both in the series flow away from the chamber, through the pumps and out to the exhaust.

My preferred location is to connect it between the blower and the chamber. Or, if there’s

a diffusion pump, I would connect it between the blower and the diffusion pump.

The last place that you might see somebody connect it is between the blower and the backing pump or a roughing pump. They might do this to use the blower almost like a turbocharger to improve the signal to the leak detector. The disadvantage of doing that is most likely these vacuum pumps are very dirty single-stage roughing pumps. There are two concerns I have with this. One is the back stream of oil or hydrocarbons from that pump to the leak detector. And the second is the potential for back streaming, even of helium from the ballast port of the pump or the exhaust, depending on where the exhaust is terminated. If somebody exhausts the pump directly out of the building, then that’s not so much a concern. But if you connect it between the blower and the diffusion pump or the blower and the chamber, then you’re allowing the roots blower to be like an optically dense filter between the leak detector and that backing pump.

And for the two concerns that I mentioned earlier about either back streaming of helium from the leak testing or back streaming hydrocarbons from the vacuum/roughing pump, the optimal location would be to hook it up between the blower and the chamber, or if it’s a diffusion pump, between the blower and the diffusion pump. If you’re hooking it up between the diffusion pump and the roughing pump, you need to make sure that you pump down to your base pressure before you open up the valve from the leak detector to that point. You don’t want to potentially suck any diffusion pump oil into the into the leak detector.

Furnace Connection Points and Hardware (00:15:50)

Doug Glenn: Is there a feed through meant for leak detection built into the furnace, between the blower and the diffusion pump or roughing pump or on the chamber?

Dave Deiwert: There is almost always a connection point where I describe my preferred location, especially with furnaces manufactured in the last twenty years. On new furnaces sold today, it’ll be an NW25 flange, which will match up directly to the leak detector.

With the leak detectors in this industry, we’ll have an NW25 flange, which is a standard vacuum connection. You run a bellows hose from that leak detector to that point on the furnace.

I like to see a manual ball valve that’s always on the furnace at that point. You can put a blank cap on the exposed port on that valve, which can act like a dust cap. It’s always there. This facilitates doing a PM leak check, which we might talk a little bit more about later.

Now, sometimes you may go to hook it up between the blower and the furnace or the blower and the diffusion pump and there’s no connection there.

I’ve seen that, so you have to work with what you’re given. You might well see there’s a port between the blower and the backing roughing pump,

and you can use that. It’s just not the optimal place to put it.

If you put the leak detector directly on the chamber, typically there’s a small port that you can hook up to, now you’re going to be competing in what we call molecular flow with a much larger opening going to the blower. The lion’s share of helium is going to go out that large target to the blower, and you’re not going to get as much helium signal to the leak detector. So, putting the leak detector port basically right into the end of the flow, going to the blower lets you sample the flow going in that direction.

Doug Glenn: Right, which is going to be the bulk of it.

Dave Deiwert: Yes, and you’ll find a faster response time and faster cleanup and recovery of the leak rate signal when you stop spraying the helium by putting it in that location.

PM Leak Checks During Furnace Operation (00:18:05)

Doug Glenn: You briefly discussed conducting PM in the column. Can you walk us through conducting a PM leak check during a live operation of the furnace.

Dave Deiwert: First off, when you’re going to do a preventative maintenance (PM) leak check on the furnace, there are two scenarios. In the first scenario, you’re not running the furnace today. So, you roll the leak detector up and you look for leaks that you may not know are there when they’re smaller and less noticeable, so you can either mark them or repair them at your convenience before they get to be larger and more noticeable, maybe affecting quality of your process.

The second scenario is that you have a very long process. You might have enough time to do a leak check while the furnace is in process. Helium is an inert gas. If you pull a vacuum on your furnace to do some heat treating, and it’s going to be in that vacuum level for an hour or more, this may be plenty of time to do some leak testing. We definitely don’t want to compromise quality. But again, helium is an inert gas, and if you have an experienced person doing this PM leak check in an orderly fashion, it can be done safely.

Basically, you roll the leak detector up to that closed ball valve, and you would have to have the ball valve in place there if you’re doing this during a live process. So you connect the hose from the test part to this closed ball valve. You start the leak detector and put it in test. I suggest that after you put it in test, you ensure you have a good vacuum test level vacuum from the leak detector to the closed valve.

Because we don’t know initially if the vacuum level is different on the other side of the valve,

Heat Treat Radio #123 Host Doug Glenn and Dave Deiwert

I recommend momentarily stopping the test of the leak detector. I think all modern leak detectors have a standby mode so you’re not venting the test for a leak detector. You put it in standby, then you open the ball valve, and the leak detector computer can now see if the vacuum level changed to maybe potentially a level a little higher than what it wants to be at. That allows it to tell itself to pull some more vacuum along with the furnace before we actually open the test valve to the analyzer cell or the mass spectrometer.

If you’re in test, you open the ball valve, and somebody forgets that step, there can be a little vacuum differential and you may shock the leak detector and throw it out of test. This doesn’t hurt the leak detector. You just have to go and press test again. But by putting it into standby and then opening the ball valve, then putting it back into test, this saves you a step.

Once you put it into test, the next thing you’re going to make a note of is the background level of helium before you start spraying helium. I’m a big fan of people who leak test their furnace, or really anything no matter what market is, and take care of their furnaces purposefully.

If you don’t suspect any leaks or it’s a brand new furnace, you can hook your leak detector up and you put it in test, and before you spray any helium, make note of what I call the background helium signal. This is a result of any natural helium that’s in the furnace. There is five parts per million helium in the air we breathe. There’s going to be helium in the furnace, and take note of what that is.

Let’s say you notice you have two times ten minus nine background of helium on the display of the leak detector, and you haven’t sprayed any helium, you can make note of that.

So now you know you’re going to be looking for leaks for some delta change increase of that value. From there, it’s playing the hot and cold game as you pinpoint where the leak isas you spray helium.

You can do this potentially while a furnace is in process. You certainly want everybody to know what you’re doing and have an opportunity to discuss this because it could make people nervous, especially the quality manager or even the production manager. It’s something that should be talked about with the whole team to ensure everybody sees the value in it.

So we spray helium and make a note of anything we see. Next time we have an opportunity, when no production is going on, we can fix that leak at our convenience rather than wait until it might get worse.

Doug Glenn: Certainly we would want to consider whether that should be done with high-value items in the furnace.

Dave Deiwert: Yes, unless everybody is on board and understands, and you’re doing things purposely.

If you are doing a PM leak check on a sensitive process and quality of a product and you’re done testing, that manual ball valve needs to be closed before you do anything else to the leak detector. If you forget, and you press vent on the leak detector, it’s going to try to vent that whole furnace through the little vent valve of the leak detector, and that’s not going to be good.

This whole discussion point is that everybody on the team would need to buy into this idea and be very clear about what we’re going to do, how we’re going to do it.

I’m just suggesting it’s something that can be done, and if you confirm it works for you, it has value. It’s just another option for somebody to optimize the way they take care of their furnace.

Confirming Leak Location Before Repair (00:23:38) 

Doug Glenn: When you’re isolating a leak, how important is it to assume or not assume that you found the leak once you get a reading on the on the meter?

Dave Deiwert: I spend a lot of time on this topic in every class that I teach because nothing is more frustrating than thinking you have found the leak when you haven’t.

Let’s say you think have found the leak on some big 10-inch gate valve. Maybe it’s too heavy for one person you have to have someone to help you take this gate valve off the system. Once you take the gate valve off the system, you put a repair kit in there, clean everything, you put it back on the furnace, and everything’s assembled. You start to furnace back up and you do a leak check and realize you still have the same leak you thought you fixed. There may be other flanges you need to check, which might require more help.

You absolutely, beyond the shadow of doubt, can know that you have found the leak because every time helium is sprayed at that place where you think the leak is, you should get the same response, same response time, same peak leak rate.

If I spray the helium at point A, where I think the leak is at, and I stop spraying, I wait for the leak rate to go back to baseline, then I go back to spray it again. The more work that is involved, the more I’m going to want to duplicate that response and make sure that is where the leak is at.

Last thing you can do, just to be sure, is what I call the “x, y, z axis.” Try to spray helium left, right, up, down, back and forth, just to make sure you’re not getting a better response to something else nearby.

Doug Glenn: By better response, do you mean a higher measurement of helium that comes through or comes through more quickly?

Dave Deiwert: That’s correct. Now, you might have the problem where there are 2, 3, or 4 connections right in the same general area, and it’s difficult to pinpoint where I’m getting I think the same response, no matter where I’m spraying the helium. To remedy this, you can put a barrier between two fittings. This barrier could be plastic, tape, putty, your hand. Try to put some barrier between the two connections so when you spray on one side now, you’re not really getting the same response you were before and can pinpoint the location of the leak more accurately.

This is an important step before you repair or remove something. If you remove a NW25 flange and you’re wrong, there’s not a lot of pain and suffering. But I guarantee you 100%, you can prove to yourself with some patience and some diligence where the leak is before you do the work of disassembly and service.

Doug Glenn: It is better to invest a little time in detection than to repair something that doesn’t need to be repaired or find out later that you fixed the wrong piece.

Dave Deiwert: Absolutely.

Repair vs. Replace: Leak Source Components (00:26:44) 

Doug Glenn: Once you do find the leak and it’s through some sort of a device, whether it’s a feed through or a control or a valve, how do you decide whether to repair that item or replace it?

Dave Deiwert: If the device is something that you can disassemble, and if the manufacturer has a repair kit (a valve is a good example of that), I would recommend that you go ahead with a repair. You have already taken it apart, I would put the part in a repair kit, if you have one, to try to lengthen the time between now and the next time you look at it.

If it’s a piece that has no repair kit, then obviously you will need to repair it or replace it, depending on your skill level and what it is you’re looking at.

If you’re looking at thermocouple and the feed screws on it are leaking, you may be a little limited in what your options are. Can you apply a vacuum-friendly sealant to brush around the feed throughs to see if that would solve the problem? That may be an option. What is the cost of that thermocouple? If it’s a $20 item, I’m probably going to put another thermocouple on there. If it’s a $1,000 item, I might try brushing some vacuum-friendly sealant on and see if that takes care of the problem.

One time, I found a leaking rotary vane pump, back in my field service days.

These all have repair kits where you can replace all the gaskets, the vanes, everything. But I didn’t have one. This was early in my young career. I talked to the factory about getting one and they were going to send one. But I told the client that we had nothing to lose. Let’s open it up, see what we can find. So, we open that pump up, and it looked pretty bad inside, but we cleaned everything up, even the gaskets, put a little vacuum sealant on, and put it all back together. We made it leak tight, and we got it running again. If I had a repair kit, I’m already there, then let’s go ahead and put the repair kit in. But if you don’t have one, there’s nothing wrong with taking it apart and seeing if cleaning and

reassembly gets it going for you.

Rotary Vane Pump Field Advice (00:30:30) 

Dave Deiwert: I’m going to give a little free advice, no extra charge, to people talking about rotary vane pumps. In my career, I’ve come across quite a number of rotary pumps that were having an issue. I can count on one hand, however, how many times I wasn’t able to just clean it, put it back together, and get it going again with fresh oil. And both those times involved a shaft seal leak. So, if you don’t have a shaft seal leak, in my mind, you’ve got nothing to lose by taking a rotary vane pump apart, cleaning it, and putting some fresh oil back in it.

If you’re using solvents, when you take it apart, make sure those are solvents cleared back out of there

because solvents and oil don’t play very nice. You want to make sure that solvents have been removed and degassed from your pump. This may require that you put oil in it, run it for a little while, then flush it, and put some oil in to make sure you don’t have anything remaining behind.

A little willingness to get your hands dirty, open up the rotary vane pump, and a very good chance that you can get it going by just doing that.

Doug Glenn: All right, Dave. Appreciate the good advice and your expertise.

About the Guest

Dave Deiwert has over 35 years of technical experience in industrial leak detection gained from his time at Vacuum Instruments Corp., Agilent Vacuum Technologies (Varian Vacuum), Edwards Vacuum, and Pfeiffer Vacuum. He leverages this experience by providing leak detection and vacuum technology training and consulting services as the owner and president of Tracer Gas Technologies.

Learn more about Dave from Heat Treat Today’s July Digital Edition’s Meet the Consultant page.

For more information: Contact Dave at ddeiwert@tracergastechnologies.com

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Heat Treat Radio #123: Helium Leak Detection Tips for Vacuum Furnace Operators Read More »

How To Find Both Real and Virtual Vacuum Leaks

April 22, 2025 / Featured, HEAT TREATING EQUIPMENT, Manufacturing Heat Treat Technical Content, VACUUM FURNACES, VACUUM FURNACES TECHNICAL CONTENT

In this Technical Tuesday installment, Thomas Wingens, Founder & President, WINGENS CONSULTANTS; Dr. Dermot Monaghan, Managing Director, and Dr. Erik Cox, Manager of New Business Development, Gencoa, train readers for finding both real and evasive virtual vacuum leaks.

Leak detection is difficult enough with a “real” leak, but “virtual” leaks present their own challenges. To enhance cost savings and further process efficiencies, it’s essential to have leak sensor technology that can effectively monitor the vacuum chamber and pinpoint these problematic leaks.

This informative piece was first released in Heat Treat Today’s March 2025 Annual Aerospace Heat Treating print edition.

Uncontrolled impurities in a vacuum furnace can significantly affect the quality of vacuum heat treating and brazing processes. They can compromise the integrity of the processed material, leading to defects, reduced performance, and increased costs.

Real vs. Virtual Leaks

Real leaks are physical openings in the vacuum system that allow external gases to enter the chamber. These can be cracks, weld failures, improperly installed fittings, faulty seals from damaged or worn O-rings on doors, rotating assemblies, or other components of the vacuum furnace.

The impact on quality includes:

Oxidation and contamination: Real leaks introduce atmospheric gases (like oxygen, nitrogen, and moisture) into the vacuum chamber, which can lead to oxidation of the materials being treated or brazed, as well as other forms of contamination.
Inconsistent results: The presence of unwanted gases can interfere with the chemical processes required for proper heat treatment or brazing, leading to inconsistent metallurgical results.
Reduced mechanical properties: Contamination and oxidation can weaken the materials being processed, leading to defects and reduced mechanical properties of the final product.
Difficulties in achieving desired vacuum: Real leaks can prevent the system from reaching or maintaining the necessary vacuum levels, leading to longer cycle times or failed processes.

Figure 1. Pumping times based on residual water vapor

Real leaks are often easier to detect, especially larger leaks, which can be identified by hissing sounds or the inability of the furnace to pump down. They can be located using methods such as pressure rise tests, solvent detection, or helium leak detectors.

Virtual leaks, however, are much harder to detect as they are not physical openings but rather trapped volumes of gas within the vacuum system that slowly release over time. These trapped volumes are typically found in blind holes, porous materials, or unvented components. Even more problematic are leaks from internally sealed systems, such as water cooling or hydraulics. Leaks from these areas cannot be detected via a leak detector, as the water or oil media can “mask” the leak site and prevent the tracer gas from penetrating.

Aside from increasing the pump time it takes to reach the required vacuum levels, leaks can be a continuous source of contamination within the vacuum chamber. Outgassing can be especially problematic during the heating cycle as it can lead to large vacuum “spikes” or a rise in pressure, affecting the stability of the process environment. Gases released from virtual leaks can contaminate the materials being treated. For example, residual solvents or water vapor from cleaning or incomplete drying can lead to contamination and outgassing. It can be small volumes of air or gas trapped at the bottom of threaded holes or trapped volumes between two O-rings that are not properly vented. Also, outgassing from various hydrocarbons in porous materials such as low-density graphite or powder metallurgy components can release unwanted gases when heated up.

They usually become apparent during the pump-down cycle when the ultimate pressures are not reached or when it takes a long time to reach blank-off pressure. Traditional leak detectors will not pick up virtual leaks.

Detecting Virtual Leaks Accurately

However, residual gas analysis (RGA) and remote plasma emission monitoring (RPEM) can identify virtual leaks by monitoring the composition of gases in the chamber. RPEM offers advantages over traditional quadrupole mass spectrometry (QMS) RGA, particularly in large vacuum systems. Unlike RGAs, RPEM technology operates over a much wider pressure range (50 mbar to 10-7mbar) without requiring additional pumps. The RPEM detector is located outside the vacuum chamber, making it more robust against contamination and high pressures, which commonly damage RGA detectors. This external setup also reduces maintenance needs, as RPEM avoids frequent rebuilds required for traditional RGAs in volatile environments.

Figure 2. Functionality and pressure range of the OPTIX sensor

An example of this newer sensor is the OPTIX, which enables real-time monitoring and process control by providing immediate feedback to maintain chemical balance and ensure product quality. By identifying specific gas species, the sensor allows versatile leak detection with faster problem-solving and continuous system monitoring. Determining the nature of the gas leak will be a clear indication of where the problem originates. Also, whether the gas levels are stable or decreasing will point towards either a real leak or outgassing problem. Unlike RGAs, this sensor does not require highly skilled staff for operation, further lowering the technical burden. Its effectiveness in harsh environments with volatile species makes it a robust and versatile tool for industrial vacuum processes.

Conclusion

By understanding the differences between real and virtual leaks, and their specific impacts on vacuum heat treating and brazing, operators can implement more effective detection and prevention strategies, ultimately leading to improved product quality and process efficiency.

Attention to design, manufacturing, and assembly processes is critical to minimize the occurrence of leaks. This includes proper venting of components, use of appropriate sealing methods, and high-quality welding. Ensuring that components and materials are properly cleaned and dried before being introduced into the vacuum system can reduce outgassing.

Regular leak checks, including leak-up-rate tests, are essential for identifying both real and virtual leaks. Advanced gas analysis techniques are very useful for identifying the type of leak and its source through analysis of the gases in the vacuum chamber. Th e method provides continuous on-line monitoring, rather than periodic leak testing when there is a “suspicion” of a problem.

In the demanding environment of vacuum heat treating and brazing, the OPTIX sensor’s advanced technology not only simplifies leak detection and process control, but also delivers significant cost savings through reduced maintenance and operational expenses. Adopting this type of technology gives operators the ability to enhance vacuum system performance, improve product quality, and achieve greater process efficiency.

About The Authors:

Thomas Wingens
Founder & President
Wingens Consultants
Industrial Advisor
Center for Heat Treating Excellence (CHTE)

Thomas Wingens is the Founder and President of Wingens Consultants, and has been an independent consultant to the heat treat industry for nearly 15 years and has been involved in the heat treat industry for over 35 years. Throughout his career, he has held various positions, including business developer, management, and executive roles for companies in Europe and the United States, including Bodycote, Ipsen, SECO/WARWICK, Tenova, and IHI-Group.

For more information: Contact Thomas Wingens at thomas@wingens.com

Dr. Dermot Monaghan
Managing Director
Gencoa

Dr. Dermot Monaghan founded Gencoa Ltd. in 1994. Following completion of a BSc in Engineering Metallurgy, Dermot completed a PhD focused on magnetron sputtering in 1992 and went on to be awarded with the C.R. Burch Prize from the British Vacuum Council for “outstanding research in the field of Vacuum Science and Technology by a young scientist.” He has published over 30 scientific papers, delivered an excess of 100 presentations at international scientific conferences, and holds a number of international patents regarding plasma control in magnetron sputter processes.

Eric Cox
Manager, New Business Development
Gencoa

Dr. Erik Cox is a former research scientist with experience working in the U.S., Singapore, and Europe. Erik has a master’s degree in physics and a PhD from the University of Liverpool. As the manager of New Business Development at Gencoa, Erik plays a key role in identifying industry sectors outside of Gencoa’s traditional markets that can benefit from the company’s comprehensive portfolio of products and know-how.

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How To Find Both Real and Virtual Vacuum Leaks Read More »

Improving Hardening and Introducing Innovation for In-House Heat Treat

March 25, 2025 / HARDENING TECHNICAL CONTENT, VACUUM FURNACES TECHNICAL CONTENT

Digital tools lead the way in vacuum hardening operations to ensure energy efficiency and processing repeatability. In this Technical Tuesday installment, Paulo Duarte, project manager at Metalsolvus, examines various advantages of wrought versus cast alloys in heat treat operations.

This informative piece was first released in Heat Treat Today's March 2025 Aerospace print edition.

Vacuum hardening has been the chosen process for hardening tools used in plastic injection, die casting, and metal sheet stamping over the past few decades. Although widely used and accepted, there is still room for improvement in tool performance through quality driven procedures. By employing easy methods of measurement, study, and testing, it is possible to enhance part integrity and mechanical properties, while simultaneously reducing heat treatment time and energy consumption. Advanced metallurgical analyses of heat treatment cycles and equipment can introduce better tools on the market, as well as provide time and cost saving heat treatments.

Basics of Vacuum Hardening

Figure 1. Cooling parts in vacuum hardening furnaces — inert gas injection on the hot chamber during cooling

In vacuum hardening furnaces, temperature and time are carefully controlled at specific load locations to ensure optimal hardening. Optimal practices focus on heating and soaking the metal parts during heat treatment. The controlled introduction of vacuum and inert gases during the process ensures the right protective atmosphere for treatment, resulting in steel that is mainly free from oxidation and decarburization. This preserves the surface integrity of the tools.

Cooling is achieved through the injection of an inert gas into the heating chamber, with controlled pressure and adequate recirculation between the heat exchanger and the hot zone (Figure 1). Different gas injection directions are utilized depending on the load being treated, ensuring optimal cooling.

Hardening of Large Tools

Figure 2. Large molds positioned inside the vacuum hardening furnace, two parallel cavities

Heating and quenching large tools is one of the most challenging situations for vacuum hardening, as temperature control and part microstructure integrity are more difficult to obtain, which affects part quality. Large tools, typically made of hot work tool steels, are hardened in large furnaces. To minimize deformation, parts are preferably positioned vertically inside the furnace (Figure 2).

Surface soaking times for big tools can significantly exceed
standard austenitization and tempering times due to thermal gradients existing within the parts. Mold cores usually achieve the right soaking and tempering recommendation through accurate temperature control, monitored by well-positioned core thermocouples. A tool’s microstructure and performance will depend heavily on geometry, size, and temperature uniformity achieved during treatment. See Figure 3 for the core and surface typical hardening cycles for large tools.

Figure 3. Heating and soaking cycle for the hardening of large tools (“Heat Treatment of a AISI H11 Premium Hot-Work Tool Steel”)

The cooling phase is crucial in determining the final properties of both the surface and core of the tool. Higher gas injection pressures result in faster cooling and increased toughness, but this also introduces greater deformation risks, when directly cooled from austenitization temperature, so martempering done at low pressures is usually required.

Balancing cooling pressure is one of the most secret topics in vacuum hardening. With a variety of parameters and procedures used among heat treaters, measuring and testing is essential for achieving consistent quality for better controlling the hardening process and attaining the best part quality.

Figure 4. Microstructure and toughness obtained after the use of different hardening cooling rates (image from Transactions of the 15th NADCA Congress, 1989)

The use of higher or lower inert gas pressures directly affects the cooling rate, making it faster or slower, respectively. Regulating the gas injection pressure during the cooling phase significantly impacts the material’s toughness, even when cooling occurs within the bainitic-martensitic domain commonly observed in vacuum hardening practices. Faster cooling leads to finer microstructures, which in turn results in tougher materials. However, fully martensitic microstructures are rarely achieved in industrial vacuum hardening furnaces and are typically limited to smaller loads composed of small parts. In larger parts, the risk of pearlite formation increases, especially when cooling rates fall around 3°C/min (5°F/min) at the core, as illustrated in Figures 4 and 5.

In industrial heat treatments of large tools, accurately monitoring core temperature is challenging, as it is difficult to position a thermocouple hole exactly at the innermost location or a nearby region. This makes it harder to control the hardening process and prevent pearlite formation. Therefore, studying the process to establish effective control measures is essential for achieving the highest possible
quality.

Figure 6. Mold temperature gradients during vacuum hardening: a) FEM mesh, b) gradients during heating at lower temperatures, c) gradients at the last pre-heating steps, and d) gradients during austenitization from Maia et al. “Study of Heating Stage of Big Dimension Steel Parts Hardening”; e) gradients during mold cooling from Pinho et al. “Modelling and Simulation of Vacuum Hardening of Tool Steels”

Heat treatment simulation simplifies this task by allowing the hardening process to be predicted, with thermal gradients estimated and compensated through furnace control parameter adjustments. Figure 6 presents a real case study, where the temperature distribution inside a large mold was fully characterized during the entire heat treatment cycle using FEM (finite element method) simulation and validated through actual thermocouple measurements. FEM simulation, as a proven and highly effective technique for predicting heat treatment cycles, enables heat treaters to implement optimized, computer-supported heat treatment practices.

Vacuum Hardening Standard Block Size and Cycle Forecast

When working with loads composed of small to medium-sized parts, the core temperature of the load can be monitored using dummy standard blocks. These blocks have a central hole to accommodate the thermocouple used to control the heat treatment cycle. The dummy block should be selected to closely match the size of the largest part in the load. However, in commercial heat treatment settings, part sizes can vary widely, making it difficult to maintain a comprehensive set of dummy blocks that represents all possible heat treatment scenarios.

Once again, simulation proves valuable in helping heat treaters gather useful data to anticipate the heat treatment cycle and determine the appropriate range of dummy blocks to have available on the shop floor. The procedure for selecting the dummy block range and forecasting the corresponding heat treatment times is outlined in the following equations. Ideally, the standard block should be made from the same material as the largest part in the load. If the materials differ, the characteristic length of the block can be calculated using the first of the equations to the right.

Table 1 lists a range of proposed dummy block sizes to be used for monitoring the load temperature during heat treatment. The time to end of soaking at higher temperature is also given by Table 1 for a typical 600 x 600 x 900 mm hardening furnace. Times were obtained by FEM simulation and can be used to forecast the end of austenitization in a hardening process of each dummy block.

Table 1. Proposed dimensional distribution range for cubic and cylindrical standard blocks and expected cycle times in a typical 600 x 600 x 900 mm hardening furnace (data from Figueiredo et al., “Study of a Methodology for Selecting Standard Blocks for Hardening Heat Treatments”)

The simulated times were validated by using real parts temperature measurement by thermocouples. These were the calculated errors based on simulation and heat treat validation trial:

Optimizing the Vacuum Hardening of Tools

Figure 7. Effect of selecting different temperature (ΔT) range for starting to control the isothermal stage time. a) ΔT criteria and respective cycle time reduction; b) surface mechanical properties obtained by using different ΔT; and c) core properties after tempering at different ΔT range (Miranda et al., “Heat Treatment of a AISI H11 Premium Hot-Work Tool Steel,” MSC)

FEM simulation can also be used to optimize the heat treatment process, but metallurgical testing remains crucial for providing reliable insights into safely reducing cycle time and energy consumption. Typically, for setting the isothermal stage time, a tolerance of -5°C relative to the temperature setpoint is used, leading to savings in both heat treatment duration and power consumption, as shown in Figure 7a. However, Figure 7b demonstrates that higher tolerance values (ΔT) can be considered. Tolerances of up to -10°C or even -20°C can be applied for controlling the soaking time without significantly affecting the hardness and toughness of the parts. Naturally, these results depend on the desired setpoints for the isothermal stages, but Figure 7c reflects the worst-case scenario for ΔT, referring to the use of lower austenitizing and tempering temperatures commonly applied in the hardening of hot-work tool steels.

Future Trends of Vacuum Hardening

Innovations like digitalization, automation, and resource reduction, as part of Industry 5.0 initiatives, are expected to drive advancements in heat treatment processes. Long martempering, a heat treatment under development for hardening hot-work tool steels, shows promise as an alternative to traditional quenching and tempering. This process offers a balance of high hardness and toughness in significantly less time, providing energy savings and faster turnaround.

New Vacuum Hardening Process — Long Martempering

Figure 8. New long martempering heat treatment cycle: AISI H13 premium toughness for two different long martempering temperatures (“Study of The Bainitic Transformation of H13 Premium Steel”)

Long martempering is a heat treatment under development that can be used to harden hot-work tool steels. Long martempering is a process somewhat similar to austempering but is applied to steels rather than cast irons. Performed at temperatures within the martempering range, long martempering corresponds to an interrupted bainitic heat treatment with a specific process window (Figure 8) where high toughness is achieved at hardness levels exceeding those obtained through traditional quenching and tempering. Table 2 lists the mechanical properties attained for 5Cr hot-work premium tool steels.

Table 2. Mechanical properties of the new hardening process — long martempering

The transformation during long martempering is not yet fully characterized in terms of microstructure, however, curved needles of bainitic ferrite are observed without carbide precipitation. This phenomenon is generally not associated with steel but rather with ausferrite in cast irons. Nonetheless, it is evident in at least H11 and H13 premium steel grades. This one day martempering treatment could potentially replace the traditional two- to three-day heat treatment cycle for large tools, offering significantly faster lead times and reduced energy consumption. Moreover, the mechanical properties achieved through long martempering are notable, as high levels of both hardness and toughness are obtained simultaneously, as demonstrated in Table 2.

Industry 5.0

Figure 9. Heat treatment plant supervision solution

The integration of heat treatment equipment with management software enhances furnace utilization, quality control systems, and maintenance practices. Industry 5.0 can be implemented in heat treatment plants through the connection of databases that collect inputs from furnaces (e.g., temperature, time, pressure, heating elements, and auxiliary equipment performance) and production data (e.g., batch numbers, order details, operator information, cycle setup, and load weight). This data is analyzed by software to generate valuable insights for plant management, process optimization, predictive maintenance, and quality control.

A supervision interface for a 5.0 solution can monitor furnaces and control them remotely in real time (Figure 9). Operators receive updates on tasks, alerts, and production schedules. Additionally, plant productivity, efficiency, and maintenance can be tracked through the same supervision software, whether on site or remote. Automatic reporting is also possible, enabling the approval or rejection of cycles based on criteria that are not typically used in heat treatment plants. This not only improves quality but also facilitates process optimization and cost reduction.

Conclusion

Acquiring a full understanding of furnaces in operation through data measurement and analysis allows full control over the heat treatment process. This facilitates process development, enabling cycle optimization and improvement in part quality. Additionally, testing and simulation practices can lead to cost reduction and shorter lead times.

The introduction of long martempering and Industry 5.0 will significantly enhance heat treatment processes, leading to improved delivery times and reduced operational risks. Automation and digitalization bring more data to the shop floor, improving plant management and resulting in greater efficiency, higher quality parts, and simplified task execution.

Finally, current personnel are busy with routine operations that are based on long established practices and may be limiting opportunities for innovation. Therefore, new teams or external consultants can be leveraged to focus on designing, studying, testing, and implementing each new heat treatment solution.

References

Fernandes, José, Laura Ribeiro, and Paulo Duarte. “Study of the Bainitic Transformation of H13 Premium Steel.” MSC thesis, Faculty of Engineering of Oporto University, 2021.

Figueiredo, Ana, Paulo Coelho, José Marafona, and Paulo Duarte. “Study of a Methodology for Selecting Standard Blocks for Hardening Heat Treatments.” MSC thesis, Faculty of Engineering of Oporto University, 2022.

Kind & Co. “Vacuum Hardening with Highest Levels of Precision.” Accessed January 30, 2025. https://www.kind-co.de/en/company/technologies/vacuum-hardening.html.

Maia, Pedro, Paulo Coelho, José Marafona, and Paulo Duarte. “Study of Heating Stage of Big Dimensions Steel Parts Hardening.” MSC thesis, Faculty of Engineering of Oporto University, 2013.

Metaltec Solutions. “Brochure Presentation.” Accessed January 30, 2025. https://www.metalsolvus.pt/en/wp-content/uploads/2019/01/plant-supervision-brochure-V3.pdf.

Miranda, Isabel, Laura Ribeiro, and Paulo Duarte. “Heat Treatment of AISI H11 Premium Hot-Work Tool Steel.” MSC thesis, Faculty of Engineering of Oporto University, 2024.

Pinho, José Eduardo, Gil Andrade Campos, and Paulo Duarte. “Modelling and Simulation of Vacuum Hardening of Tool Steels.” MSC thesis, Aveiro University, 2017.

Ramada. “New Hardening Furnace up to 4 Tons.” Accessed January 30, 2025. https://www.ramada.pt/pt/media/noticias/novo-forno-de-tempera-vacuo---ate-4-tons-.html.

Schmetz. “Schmetz Heat Treatment Furnaces.” Accessed January 30, 2025. https://edelmetal.com.tr/en/heat-treatment-furnaces.

Schmetz. Sketch of the Cooling Process in the Vacuum Hardening Furnace: Schmetz Commercial Proposals Drawing – Metalsolvus Training Courses Documentation.

Seco/Warwick. Vector 3D Hardening Furnace Commercial Brochure.

Solar Manufacturing. “Solar Vacuum Hardening Furnace.” Accessed January 30, https://solarmfg.com/vacuum-furnaces-horizontal-iq-vacuum-furnaces.

Wallace, J.F., W. Roberts, and E. Hakulinen. “Influence of Cooling Rate on the Microstructure and Toughness of Premium Grade H13 Die Steels.” Transactions of the 15th NADCA Congress (1989).

About The Author:

Paulo Duarte, project manager at Metalsolvus, is a researcher and consultant on heat treat technologies. His education and expertise in metallurgy has culminated in several articles and patents. He was a former technical manager within bohler-uddeholm group for the Portuguese market and heat treatment manager with the same group. Currently, Paulo focus on helping heat treaters by providing innovative, more efficient, and profitable heat treatment services to companies.

For more information: Contact Paulo Duarte at paulo.duarte@metalsolvus.pt.

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Why Normalize, and Is a ‘Still Air’ Cool Really Important? Part 2

March 13, 2025 / ATMOSPHERE AIR FURNACES TECHNICAL CONTENT, HARDENING TECHNICAL CONTENT, Manufacturing Heat Treat Technical Content, VACUUM FURNACES TECHNICAL CONTENT

The Heat Treat Doctor® has returned to offer sage advice to Heat Treat Today readers and to answer your questions about heat treating, brazing, sintering, and other types of thermal treatments as well as questions on metallurgy, equipment, and process-related issues.

This informative piece was first released in Heat Treat Today’s March 2025 Aerospace Heat Treating print edition.

Last time (Air & Atmosphere Heat Treating, February 2025) we addressed the question of why normalizing is necessary. Here we look at the importance of a “still air” cool on the final result. Let’s learn more.

What Is a “Still Air” Cool?

As we learned last month, the term “cooling in air” is associated with normalizing but poorly defined in the literature or in practice, either in terms of cooling rate or microstructural outcome. This lack of specificity has resulted not only in many different interpretations of what is needed, but in a great deal of variability in the final part microstructure.

By way of example, this writer has on multiple occasions asked what changes are made to car bottom furnace cycles where cars are pulled outside of the plant for “air cooling” (Figure 1). Questions such as, is the furnace opened and the car pulled out in inclement weather? And, is this practice done on a particularly windy day, or in a rain or snowstorm or when the temperature is below zero? An all-too-common response is, “Only if it isn’t raining ‘too hard’ or snowing ‘too much’; then, we wait a while.” No wonder part microstructures are often found to vary from part to part and load to load!

Most heat treaters agree, however, that normalizing is optimized by a cooling in “still air.” This term also hasn’t been clearly defined, but it will be here based on both an extensive survey of the literature and the most common heat treat practices. In Vacuum Heat Treatment, Volume II, I define a still air cool as: “Cooling at a rate of 40°F (22°C) per minute … to 1100°F (593°C) and then at a rate of 15°F–25°F (8°C–14°C) per minute from 1100°F (593°C) to 300°F (150°C). Any cooling rate can be used below 300°F (150°C).”

Typical car bottom normalizing furnace opening to the outside environment

In addition, many consider nitrogen gas quenching in a vacuum furnace at 1–2 bar pressure to be equivalent to a still air cool. But again, so many factors are involved that only properly positioned workload thermocouples can confirm the above cooling rates are being achieved.

Also, many use the term “air cooling” to differentiate the process from “air quenching,” “controlled cooling,” and “fan cooling.”

Recall from the previous installment of this column that any ambiguity with respect to cooling rate ought to be defined in engineering specifications and/or heat treat instructions so that the desired outcome of the process can be firmly established.

From the literature, several important observations will serve as cautionary reminders. In STEELS, George Krauss points out that: “Air cooling associated with normalizing produces a range of cooling rates depending on section size [and to some extent, load mass]. Heavier sections air cool at much lower cooling rates than do light sections because of the added time required for thermal conductivity to lower temperatures of central portions of the workpiece.”

George Totten’s work in Steel Heat Treatment indicates: “Cooling … usually occurs in air, and the actual cooling rate depends on the mass which is cooled.” He goes on to state:

After metalworking, forgings and rolled products are often given an annealing or normalizing heat treatment to reduce hardness so that the steel may be in the best condition for machining. These processes also reduce residual stress in the steel. Annealing and normalizing are terms used interchangeably, but they do have specific meaning. Both terms imply heating the steel above the transformation range. The difference lies in the cooling method. Annealing requires a slow [furnace] cooling rate, whereas normalized parts are cooled faster in still, room-temperature air. Annealing can be a lengthy process but produces relatively consistent results, where normalizing is much faster (and therefore favored from a cost point of view) but can lead to variable results depending on the position of the part in the batch and the variation of the section thickness in the part that is stress-relieved.

In “The Importance of Normalizing,” this writer offers the following caution: “It is important to remember that the mass of the part or the workload can have a significant influence on the cooling rate and thus on the resulting microstructure.”

Finally, Krauss again observes: “The British Steel Corporation atlas for cooling transformation (Ref. 13.7) establishes directly for many steels the effect of section size on microstructures produced by air cooling.” (Note: Interpretation of continuous cooling transformation (CCT) curves will be the subject of a future “Ask The Heat Treat Doctor” column.)

Since hardness is one of the most commonly used criteria to determine if a heat treat process has been successful, it should also be noted that one can usually predict the hardness of a properly normalized part by looking at the J40 value when Jominy data is available.

The Metallus (formerly TimkenSteel) “Practical Data for Metallurgists” provides an example of the type of data available to metallurgists and engineers to help define a required cooling rate for normalizing (Figure 2).

All literature references to normalizing agree (or infer) that the resultant microstructure produced plays a significant role in both the properties developed and their impact on subsequent operations.

Figure 2. Combined hardenability chart for normalized and austenitized SAE 4140 steel showing approximate still air cooling rates and resultant hardness (data based on a thermocouple located in the center of the bar diameter indicated)

Final Thoughts — The State of the Industry

It is all too common within the industry for some companies who wish to have normalizing performed on their products to specify only a hardness range on the engineering drawing or purchase order callout that is given to the heat treater.

Industry normalizing practice here in North America varies considerably from company to company. Normalizing instructions are sometimes, but not often enough, provided on either purchase orders, engineering drawings, or in specifications (industry standards or company-specific documents). These instructions range from, in the case of certain weldments, absolutely nothing (i.e., no hardness, microstructure, or mechanical properties) to referencing industry specifications (e.g., AMS2759/1) or specifying complete metallurgical and mechanical testing including hardness and microstructure.

Most commercial heat treaters often perform normalizing to client or industry specifications provided to them. Others prefer so-called “flow down” instructions in which the process recipe is provided to them. It is a common (and mistaken) belief that this removes the obligation of achieving a given set of mechanical or metallurgical properties even if they are called out by specification, drawing, or purchase order.

Also, the final mechanical properties that result from normalizing are seldom verified by the heat treater. Rather, a hardness value (or range) is reported, but hardness is not a fundamental material property, rather a composite value, one which is influenced by, for example, the yield strength, work hardening, true tensile strength, and modulus of elasticity of the material.

References

ASM International. “ASM Handbook, vol. 4, Heat Treating,” 1991.

ASM International. “ASM Handbook Volume 4A, Steel Heat Treating, Fundamentals and Processes,” 2013.

Chandler, Harry, ed. Heat Treater’s Guide: Practices and Procedures for Irons and Steels. 2nd ed, ASM International, 1995.

Grossman, M. A., and E. C. Bain. Principles of Heat Treatment, 5th ed, ASM International, 1935.

Herring, Daniel H. Atmosphere Heat Treatment, vol. I, BNP Media, 2014.

Herring, Daniel H. Atmosphere Heat Treatment, vol. II, BNP Media, 2015.

Herring, Daniel H. Vacuum Heat Treatment, vol. I, BNP Media, 2012.

Herring, Daniel H. Vacuum Heat Treatment, vol. II, BNP Media, 2016.

Herring, Daniel H. “The Importance of Normalizing,” Industrial Heating April 2008.

Krauss, George. STEELS: Heat Treatment and Processing Principles, ASM International, 1990. 463.

Krauss, George. STEELS: Processing, Structures, and Performance, ASM International, 2005.

Practical Data for Metallurgists, 17th ed. TimkenSteel, 2011

Totten, George E., ed. Steel Heat Treatment Handbook, vol. 2, 2nd ed., CRC Press, 2007.

About the Author

Dan Herring
“The Heat Treat Doctor”
The HERRING GROUP, Inc.

Dan Herring has been in the industry for over 50 years and has gained vast experience in fields that include materials science, engineering, metallurgy, new product research, and many other areas. He is the author of six books and over 700 technical articles.

For more information: Contact Dan at dherring@heat-treat-doctor.com.

For more information about Dan’s books: see his page at the Heat Treat Store.

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What Is Thermal Expansion?

January 20, 2025 / Manufacturing Heat Treat Technical Content, OP-ED, STRESS RELIEVING TECHNICAL CONTENT, VACUUM FURNACES TECHNICAL CONTENT

This informative piece was first released in Heat Treat Today’s December 2024 Medical & Energy Heat Treat print edition.

The subject of thermal expansion and contraction is a very important one to most heat treaters given that the materials of construction of our furnaces and our fixtures experience these phenomena every day. However, to find a simple explanation of what it is and how we can help minimize the issues caused by it can be difficult. What we need is an explanation in laymen’s terms, along with some simple science and a few examples. Let’s learn more.

Thermal Expansion Effects

When exposed to a change in temperature, whether heating or cooling, materials experience a change (increase or decrease) in length, area, or volume. This not only changes the material’s size but also can influence its density. The freezing of ice cubes is a common example of a volume expansion (on freezing or cooling), while as they melt (on heating), we see a volume contraction.

As most of us recall from our science classes, as temperature increases, atoms begin to move faster and faster. In other words, their average kinetic energy increases. With the increase in thermal energy, the bonds between atoms vibrate faster and faster creating more distance between themselves. This relative expansion (aka strain) divided by the change in temperature is what is known as the material’s coefficient of linear thermal expansion.

We must also be aware, however, that a number of materials behave in a different way upon heating. Namely, they contract. This usually happens over a specific temperature range. Tempering of D2 tool steel is a good example (Figure 1). From a scientific point of view, we call this thermal contraction (aka negative thermal expansion).

Figure 1. Change in length of D2 tool steel as a function of tempering temperature (Image courtesy of Carpenter Technology — www.carpentertechnology.com)

A related fact to be aware of is that thermal expansion generally decreases with increasing bond energy. This influences the melting point of solids, with higher melting point materials (such as the Ni-Cr alloys found in our furnaces and fixtures) more likely to have lower coefficient of thermal expansion. The thermal expansion of quartz and other types of glass (found in some vacuum furnaces) is, however, slightly higher. And, in general, liquids expand slightly more than solids.

Effect on Density

As addressed above, thermal expansion changes the space between atoms, which in turn changes the volume, while negligibly changing its mass and hence its density. (In an unrelated but interesting fact, wind and ocean currents are, to a degree, effected by thermal expansion and contraction of our oceans.)

What Is the Effect of the Coefficient of Thermal Expansion?

In laymen’s terms, the coefficient of thermal expansion (Table 1) tells us how the size of an object changes with a change in temperature. Specifically, it measures the fractional change in size per degree change in temperature at a constant pressure. Lower coefficients describe lower tendency to change in size. There are several types of thermal expansion coefficients — namely linear, area, and volumetric. For most solid materials, we are typically concerned in the heat treat industry with the change along a length, or in some cases a change in volume (though this is mainly of concern in liquids).

Table 1. Comparative values for linear and volumetric expansion of selected materials

Heat Treat Furnace Examples

When calculating thermal expansion, it is necessary to consider whether the design is free to expand or is constrained. Alloy furnace muffles, retorts, mesh and cast link belts, and radiant tubes are good examples. The furnaces that use them must be designed to allow for linear growth and changes in area or volume. If not, the result is premature failure due to warpage (i.e., unanticipated movement).

If a component is constrained so that it cannot expand, then internal stress will result as the temperature changes. These stresses can be calculated by considering the strain that would occur if the design were free to expand and the stress required to reduce that strain to zero, through the stress/strain relationship (characterized by Young’s modulus). In most furnace materials it is not often necessary to consider the effect of pressure change, except perhaps in certain vacuum furnaces or autoclave designs.

A Little Science

For those that are interested, here are the formulas most often used by heat treaters to calculate the coefficient of thermal expansion.

Estimates of the Change in Length (L), Area (A), and Volume (V)

Linear expansion is best interpreted as a change in only one dimension, namely length. So linear expansion can be directly related to the coefficient of linear thermal expansion (α_L) as the change in length per degree of temperature change. It can be estimated (for most of our purposes) as:

where:

ΔL is the change in length
ΔT is the change in temperature
α_L is the coefficient of linear expansion

This estimation works well as long as the linear expansion coefficient does not change much over the change in temperature and the fractional change in length is small (ΔL/L <<1). If not, then a differential equation (dL/dT) must be used.

By comparison, the area thermal expansion coefficient (α_A) relates the change in a material’s area dimensions to a change in temperature by the following equation:

where:

ΔA is the change in area
ΔT is the change in temperature
α_A is the coefficient of area expansion

Again, this equation works well as long as the area expansion coefficient does not change much over the change in temperature ΔT(ΔT), if we ignore pressure and the fractional change in area is small (ΔA/A <<1)ΔA/A<<1. If either of these conditions does not hold, the equation must be integrated.

For a solid volume, we can again ignore the effects of pressure on the material, and the volumetric (or cubical) thermal expansion coefficient can be written as the rate of change of that volume with temperature, namely:

where:

• ΔV is the change in volume
• ΔT is the change in temperature
• α_V is the coefficient of volumetric expansion

In other words, the volume of a material changes by some fixed fractional amount. For example, a steel block with a volume of 1 cubic meter might expand to 1.002 cubic meters when the temperature is raised by 90°F (32°C). This is an expansion of 0.2%. By contrast, if this block of steel had a volume of 2 cubic meters, then under the same conditions it would expand to 2.004 cubic meters, again an expansion of 0.2% for a change in temperature of 90°F (32°C).

Thermal Fatigue

In many instances, we must consider the effect of thermal fatigue as well as thermal stress. One example is on the surface of a hot work die steel as H11 or H13: one must ensure that in service, when it experiences a (rapid) change in temperature, it will avoid cracking.

The equation for thermal stress is:

where:

σ is the thermal stress
E is the Young’s modulus of the material at temperature
α is the coefficient of linear thermal expansion at temperature
ΔT is the change in temperature

Here both E and α depend on temperature and the resultant stress will either be compressive if heated or tensile if cooled, so we must use these constants at both maximum and minimum temperatures. Considering the temperature dependent stress-strain curve, this stress may exceed the elastic limit (tensile or compressive) and contribute eventually to thermal fatigue failure. There are software programs to aid in the calculation of the resultant thermal stresses. Thermal expansion at a surface at a higher temperature than the core results in a compressive stress, and vice versa.

Final Thoughts

The effects of thermal expansion will be highlighted in a forthcoming article in Heat Treat Today, but it suffices for all heat treaters to remember that this phenomenon is responsible for a great deal of downtime and maintenance in our equipment. It also can affect the end product quality (disguising itself as distortion) and hence create additional cost or performance issues for our clients.

References

Chandler, Harry, ed. Heat Treater’s Guide: Practices and Procedures for Irons and Steels, 2nd Edition. ASM International, 1995.

Herring, Daniel H. Vacuum Heat Treatment. BNP Media, 2012.

Herring, Daniel H. Vacuum Heat Treatment Volume II. BNP Media, 2016.

Special thanks to Professor Joseph C. Benedyk for his input on the topic.

About the Author

For more information: Contact Dan at dherring@heat-treat-doctor.com.

For more information about Dan’s books: see his page at the Heat Treat Store.

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The Heat Treat Robotic Paradigm Shift

January 14, 2025 / Manufacturing Heat Treat Technical Content, TECHNOLOGY, VACUUM FURNACES TECHNICAL CONTENT

As Thomas Bauernhansl, professor of Production Technology & Factory Operations at the University of Stuttgart, aptly states, “We are going from more supply-oriented production to a demand-oriented one. In many cases, the customer determines which version he wants to have [of] a product — the manufacturer adapts to this and his processes accordingly.”

This shift is critical for the heat treat industry, where the need for advanced automation and robotics integration is paramount to achieve higher efficiency, consistent quality, and reduced costs. In this Technical Tuesday, Dennis Beauchesne, general manager at ECM USA, discusses the increase in use and installation of automation and robotics in manufacturing and specifically how companies within the heat treat industry have adapted to their implementation—and become innovators in their usage.

This informative piece was first released in Heat Treat Today’s January 2025 Technologies To Watch in Heat Treating print edition.

Industry Automation

In the last 10–15 years, an upward trend is consistent with the increased investment value of integrated automation within a heat treatment plant. At the beginning of the 2000s, it was common to have an automatic transport car transporting batches to different stations, but, in the last five years, far more complex automation solutions are in demand. In order to meet the requirements of future industry robotics and automation, our industry must adapt to the new and improved technology offerings and standards that are being used in other industries.

Figure 1. Annual robotics installation by industry 2021-2023

According to World Robotics, there has been a significant increase in robotics usage and installations since 2020 (Figure 1). For example, the automotive industry shows installations almost doubled from 2020 to 2022 with 83,000 installations in 2020, compared to 136,000 installations in 2022. The industrial robot market was expected to grow by 7% in 2023 to more than 590,000 units worldwide. Although it exceeded 500,000 installations, robotics were down 2% (possibly due to COVID-19) compared to the prior record year. Of interest to note for the automotive industry, the industry increased its robotics demand in 2023 to surpass electronics with a 25% share (electronics was close with 23%, down by 5% due to inventory levels stabilizing after supply chain bottlenecks mostly vanished).

Table 1. North America’s robotics comparison 2022 to 2023
Source: World Robotics

Specifically for the United States and Mexico, peak robotics installation demand was documented in 2022, but demand has been consistent within +/-5% (Table 1). The future of robot installations is trending to grow and exceed 50,000 units in North America for 2024. Nearshoring of supply chains will create demand for automation technology in the years to come, according to Christopher Müller in his World Robotics 2024 – Industrial Robots presentation.

Manufacturing Concepts

The company SEW has previously published its ideas and concepts of autonomous transporters distributing the raw parts to the production cells, after the soft processing to the hardening plant, and finally the hard machining (Figure 2). All steps are configured within the component so the process steps can be well documented on a component basis.

Figure 2. SEW concept from Hiller, “The networked hardening shop,” 2019
Source: ECM GmbH

As can be seen in the SEW Figures, the original hardening plant is shown as a continuous furnace. However, this type of plant technology can be seen as contradictory to current production needs. To be compliant with this new philosophy, plant technology must be as modular, flexible, and automatable as the rest of the production layout and components. Heat treatment must also be controllable and unloadable with automatic transport units. Robots must be able to load batches and navigate the plant (according to CHD, steel, part numbers, etc.). The smaller the batch size, the larger the value of robotic component documentation. Furthermore, a reduction in batch size is advantageous for flexibility, costs, and heat treatment of many requirements for production runs.

Heat Treatment & Robotics

A heat treatment plant can implement
recommendations for the future of industry
automation by acquiring technology for:

Automatic loading/unloading
Component recognition systems
Automatically loaded/read recipe systems
Smaller batch sizes with a wide variety of variants
Heat treatment of different applications or steels in small quantities
Maintenance/repair detection

Benefits of automating part or all production line steps include:

Shorter process times
High CHD (Case Hardening Depth) uniformity and lower distortion
Lower operating costs and labor reduction

These technologies have existed and are being implemented in heat treat operations for a few years now. The results are clear and the benefits are proven through higher quality parts, highly efficient heat treat operations, and overall more efficient production facilities.

As many machining operations have been robotized, this allows the downstream heat treat operations to easily take advantage of part placement in dunnage and plant transport systems, whether manual or automated.

Figure 3. ECM Vision System
Source: ECM Robotics

Batch Loading with Robotics

Bulk goods-loading (such as clips, links, and other small parts via weight detection) as well as loading and unloading of truck shafts in fixtures and in straightening machines are just a few examples of production areas that can benefit from robotics/automation. Visual recognition systems can identify gears/parts based on the diameter or by the number of teeth on the gear and can then sort them by these features (Figure 3).

Like the visual locating of the parts by cameras, they can also be used for tracking parts and loads within a heat treatment cell. A good amount of work has been done in this area for heat treating. This work covers part marking, tray/fixture encoding, and part weighing scenarios, and allows the heat treat system to accurately process all the different parts coming through the heat treat system with the correct process recipe.

Some of the work being done has been implemented with a QR code marking system for each part before heat treatment. To ensure the correct recipe or heat treatment is performed on the proper part, this scanned code works with the heat treatment system controls to upload the correct recipe to the proper cell. This information can be further analyzed to indicate precise placement in the heat treat tray through virtual tracking.

Figure 4. QR code heat treat test picture
Source: ECM USA Synergy Center

In Figure 4, you can see in the details that this client has reviewed and tested to assure the code is visible before and after heat treating with a carburizing and hardening process.

These parts are tracked when entering the system and also noted as to which heat treat tray they are on by using a binary code with holes in a tray or on a strategically placed bar code plate on the tray. With this system, they can be scanned by a camera before entry and upon exit of the furnace (Figure 5). This tray scanning can also indicate how many cycles the trays have on them to ensure the trays stay in good condition and can be cycled efficiently.

Figure 5. Lohmann Steel barcode scan plate (Images courtesy of Lohmann Steel, heat resistant castings — grates, trays, baskets, fixtures and more)
Source: Lohmann Steel

Networked Hardening

Let’s look at the SEW production concept again and re-imagine it with a more efficient vacuum furnace technology with robotic integration. In this concept, the vacuum furnace system forms the “spatially distributed production reserve” which helps autonomous transport units as “situationally self-controlling” material is delivered.

The QR code on the component represents the “knowledge-based” running card. The robots recognize the components by means of the QR code and are loaded onto the appropriate heat treat trays. The heat treatment can then be carried out on a component-related, flexible, and documented basis. Traceability of production can also be ensured (Figure 6).

Figure 6. Robotics concept
Source: ECM Technologies

Loading of the parts can be done efficiently through a series of dunnage that hold the part in specific locations which assist the robot to locate, lift, and place the parts in the heat treat tray. This method doesn’t always need to be a perfect location for the incoming work as we now have 2D and 3D cameras that can work in tandem to locate parts, even in odd stacking or randomly loaded bins.

In a recent installation, a heat treater automated their gear cutting operation to prepare the dunnage before heat treat. Therefore, the heat treat robotics phase was simplified by storing each part in a specification location for the robot to “see” with its vision system. These parts are then scanned and automatically connected to the part’s recipe as stored in the system. In a modular system using low pressure carburizing, individual cells are utilized, and production is recipe driven. These recipes are pre-developed and stored to allow each cell to utilize the recipes for many different parts. In this case, after a part is scanned, the recipe is uploaded into the next available cell and the scanned parts and heat treat fixture is moved to the cell (Figure 7).

Figure 7. Modular vacuum furnace for low pressure carburizing
Source: ECM USA

Figure 8 was designed to use over 175 different parts with nine different heat treat processes which included carburizing and slow cooling, hardening, tempering, cooling after tempering and cryogenic treatment.

With further considerations for additional benefits of the automated system, fixtures were optimized by using CFC (carbon fiber composite) base trays. These trays are not only extremely stable and have non-existent growth/warpage, but they also help with robotic placement before and after heat treatment. CFC trays are flat, or can be machined to conform to part geometry, which helps to reduce or minimize distortion related to fixture warpage or creep.

Figure 8. LPC and robotics configuration
Source: ECM USA

Many system designs have been proposed to a variety of clients; however, the end goal is to design a system that is “standard.” This standard design needs to incorporate different forms of dunnage, bins, boxes, and pallets to allow a commercial heat treater to easily program the system whenever the next part comes in from their client, whatever it may be. This is a challenging task and needs to be broken out by weight category to design the robot’s reach and end tool design. In this case a robot cell offline of the heat treat furnace can be built and utilize, and ultimately use, an AMR (automated mobile robot) or AGV (automated guided vehicle) to bring the built loads to the furnaces (Figure 9).

Figure 9. AGV configurations
Source: ECM GmbH & ECM Technologies

Vacuum Advantages

Vacuum furnace systems have a clear advantage over traditional atmospheric systems with many features which lend themselves to integrate into the machining area with robotics and automation.

The fact that an LPC (low pressure vacuum) furnace system can process loads via a recipe input and each cell can be used to process a different case depth, or hardening cycle is highly advantageous when processing a wide variety of parts. In addition, the LPC process provides a more uniform case depth throughout the part to make a stronger part along with high quality processing. The vacuum furnace cells can be arranged in many ways to fit into existing facilities and to be able to use many methods of automation especially including robotics.

Quenching is also a key element in any hardening heat treat process. LPC furnace systems are usually associated with high pressure gas quenching (HPGQ) in a separate chamber to provide the best quenching performance. This gas quenching technique provides a clean process for each part and allows the use of CFC fixtures. There is also no requirement for post cleaning as is necessary with oil quenching.

Providing quality low pressure carburizing, clean and precise gas quenching, CFC trays for better uniformity and keeping the parts flat, and the automation benefits of robotics makes for a state-of-the-art heat treating production operation and thus completes the heat treat paradigm shift.

Figure 10. Robot loading
Source: ECM USA

Conclusion

The heat treat industry wants and needs automation and robotics integration to advance production, reduce costs, and improve the overall quality of production. With traditional technology, process data evaluation and self-configured recipe values are not possible. Therefore, component analysis should be automated to meet and achieve consistent and reliable recipe values (mass flow, time). With the increase in robotics demand, vacuum furnace technology meets the variable requirements of “demand-oriented” production. Due to the flexibility of this technology, small batch size systems can be automated with robots or as bulk material.

References

Hiller, Gerald. “The networked hardening shop – the challenge to the hardening plant in the world of Industry 4.0.” ECM GmbH. Paper presentation, 2019.
Müller, Christopher. “World Robotics 2024 – Industrial Robots.” IFR Statistical Department, VDMA Services GmbH, presentation in Frankfurt am Main, Germany, 2024.

About the Author:

Dennis Beauchesne brings experience of over 200 vacuum carburizing cells installed on high pressure gas quenching and oil quenching installations. He has worked in the thermal transfer equipment supply industry for over 30 years, 23 of which have been with ECM USA.

For more information: Contact Dennis at DB@ECM-USA.com.

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