VACUUM FURNACES TECHNICAL CONTENT

Hypersonics Come Alive with Vacuum and Controlled Atmosphere Furnaces

/ AEROSPACE HEAT TREAT TECHNICAL CONTENT, ATMOSPHERE AIR FURNACES TECHNICAL CONTENT, SINTERING POWDER/METAL TECHNICAL CONTENT, VACUUM FURNACES TECHNICAL CONTENT

Hypersonic vehicles and missiles operating at Mach 5 and beyond place unprecedented thermal and environmental demands on aerospace materials. In this Technical Tuesday installment, Scott Robinson, product manager of ceramics and powder metallurgy at Centorr Vacuum Industries, examines how vacuum and controlled-atmosphere furnaces support the research, prototyping, and production of ultrahigh-temperature ceramics, carbon–carbon composites, and other advanced materials used in hypersonic applications.

This informative piece was first released in Heat Treat Today’s March 2026 Annual Aerospace Heat Treating print edition.

Introduction

Hypersonic missiles and vehicles are an emerging class of aerospace technology that is developing rapidly toward active use in military and potentially commercial applications. These machines can achieve sustained speeds of Mach 5 or greater within the Earth’s atmosphere (i.e., at altitudes below about 90 km). While conventional intercontinental ballistic missiles can also achieve hypersonic speeds during atmospheric reentry, they follow a high-arching ballistic trajectory with limited maneuverability, in contrast to the real-time in-flight maneuverability offered by hypersonic systems. As such, military actors prefer hypersonic missiles for precision strikes (Mesa 2024), while in the commercial realm, airliners are excited by the possibility of drastically shortened journey durations with hypersonic vehicles (TomorrowDesk 2025).

Because hypersonic missiles and vehicles move at extreme speeds within Earth’s atmosphere, they are subject to significant atmospheric compression and friction effects (Smith 2021). These effects result in considerable aerodynamic heating of the leading edges, nose tips, and exhaust-washed structures, from 1800°C (3200°F) to more than 3000°C (5400°F).

Traditional aerospace materials such as aluminum, stainless steel, and titanium cannot be used at these elevated temperatures without thermal protection engineering. In contrast, an emerging portfolio of materials including refractory metals, carbon-carbon composites, ultrahigh-temperature ceramics (UHTCs), and ceramic matrix composites (CMCs) can more easily deal with this extreme heat.

UHTCs and CMC materials typically are composed of metal carbides, borides, and nitrides, which means they are traditionally processed at very high temperatures. Currently, the leading candidate materials are silicon carbide (melting/decomposition point: 2730°C, or 4945°F) and zirconium diboride (melting point: ~3246°C, or 5875°F) due in part to their reasonable raw material costs.

Processing of UHTCs, CMCs, and other advanced materials for aerospace applications includes one or more of the following high-temperature processing steps, often using vacuum and controlled atmosphere furnace technology:

  • Chemical vapor infiltration
  • Chemical vapor deposition
  • High-temperature sintering
  • Graphitization
  • Silicon melt infiltration of carbon-carbon composites

Each stage of the product development cycle — from laboratory-scale research and development to prototype development to production-scale manufacturing — requires a portfolio of specialized furnaces to achieve the goals of each stage.

This article takes a closer look at the types of furnace solutions available to develop, process, and commercialize these high-performance materials.

Laboratory-Scale Research and Development


Figure 1. a) Centorr Vacuum Industries’ LF 3000°C (5400°F) graphite vacuum furnace and b) top view of hot zone; 3” x 4” (75 x 100 mm; Ø x h) hot zone. | Image Credit: Centorr Vacuum Industries

Laboratory-scale R&D activities focus mostly on the development, fabrication, and testing of small-scale parts, which require a small, adaptable furnace.

The LF graphite vacuum furnace is an example of the type of furnaces needed for small-scale parts (Figure 1). First designed in 2012, it is a robust, low-cost development furnace with temperature capability up to 3000°C (5400°F) in vacuum or inert gas. This temperature range covers most hypersonic, UHTC, and other applications. For example, current users fit the small 3″ x 4″ (75 x 100 mm; Ø x h) hot zone with small graphite crucibles to fire graphite-based powders for applications in battery and electric vehicle technology.

In another case, Dalhousie University in Nova Scotia, Canada, a research-based university, modified the base LF system by adding a small binder/off-gassing trap and positive pressure exhaust tower for processing of non-oxide ceramics produced by additive manufacturing. These samples include silicon-based ceramics (silicon carbide and silicon nitride), high-entropy ceramics, and cermet systems.

Subsequent laboratory applications require a larger hot zone furnace for processing bigger samples. One example of this type of furnace is the Series 10 graphite tube furnace (Figure 2). This tube furnace is based on a more than 50-year-old furnace design, although the traditional alumina or quartz tube has since been replaced with a solid graphite tube. Operating in vacuum or partial/positive pressures of argon, R&D centers use this furnace to process carbon powder formulations to maximize the percent conversion to graphite, as not all carbon-based starting materials will convert to crystalline graphite.

Figure 2. Series 10 3000°C (5400°F) graphite tube furnace; 4″ x 16″ (100 mm x 400 mm) hot zone diameter and height. Image Credit: Centorr Vacuum Industries

Figure 3. a) Series 45 graphite top-loading furnace and b) top view of hot zone. Used for carbon/graphite work, this model offers a larger useable firing footprint at higher temperatures than the Series 10 furnace. The hot zone diameter and height dimensions approximate 6″ x 6″ (150 mm x 150 mm), and temperature is rated for 3200°C (5790°F). | Image Credit: Centorr Vacuum Industries

As R&D activities begin to focus on particular material compositions, larger furnaces are needed to synthesize meaningful sizes and quantities of candidate materials prior to scaling up for manufacture, like the Series 45 graphite top-loading furnace (Figure 3).

Characterization and Prototyping Stage


Figure 4. Front view of the Series TT Testorr graphite hot zone rated for 2700°C (4890°F) processing temperatures | Image Credit: Centorr Vacuum Industries

Once the final candidate materials are processed, aerospace design engineers need to test meaningfully sized samples of the materials at high temperature under mechanical loading. It is best to have a furnace that can be combined with mechanical test stands to take measurements of mechanical properties. This is the case for Wichita State University’s National Institute for Aviation Research, which leverages multiple Testorr® furnace units to measure tension, compression, and shear properties of ceramic matrix composites, refractory metals, and other materials at high temperature. Rated for temperatures up to 2700°C (4890°F) in vacuum or inert gas, the furnace can better simulate some aspects of hypersonic service environments (Figure 4).

An important task of the R&D and prototyping stages is to work out processing parameters that will be translated to production-scale manufacturing processes. For example, simple carbon structures will react with air during reentry and suffer damaging effects at temperatures as low as 500°C (930°F). Therefore, any carbon-carbon materials or solid carbon shapes used in hypersonic applications must be protected with advanced ceramic coatings for durability and oxidation resistance.

Chemical vapor deposition is one such coating deposition process, and one of the most popular protective coatings is silicon carbide. The coating is deposited on substrate parts by flowing hydrogen gas through a bubbler of liquid methyltrichlorosilane (MTS; CH3SiCl3) gas. Newer systems use a heated evaporator to vaporize the MTS liquid in a hydrogen carrier gas stream. The combination of hydrogen and MTS is introduced at partial pressures into the furnace hot zone inside a graphite retort, where the gases “crack” or decompose, depositing microns-thick coatings of silicon carbide onto the part’s surface.

Production Stage

Once the advanced materials are properly characterized and prototyped, it is time to look at equipment for full-scale production manufacturing. The furnace configurations for these processes can be conventional front-loading designs or may be oriented in vertical top- or bottom-loading designs for floor space savings and gas flow dynamics.


Figure 5. Production-size Sintervac vacuum furnace for processing carbon-carbon melt infiltration composite materials | Image Credit: Centorr Vacuum Industries

The Sintervac® front-loading graphite furnace (Figure 5) has integral graphite retort and dual gas flow to the main chamber and retort. These furnace systems include durable rotary piston pumping systems with inline binder traps and particulate filters to protect the pumping systems from damage from abrasive ceramic particulates. The internal graphite retort compartmentalizes the off-gassing that takes place and prevents it from escaping into the hot zone, where the oxide byproducts can attack and degrade the graphite heating elements and rigid graphite board insulation.

One common application for this type of furnace is melt infiltration of carbon-carbon composites to improve the physical properties and oxidation resistance of the composite. When processed in partial pressures (or even at positive pressures) of argon, silicon will melt at approximately 1450°C (2640°F). The silicon liquid and vapor infiltrate into the void spaces of the porous carbon-carbon composite via capillary action. The infiltrated silicon reacts with the free carbon in the carbon-carbon fiber structure, forming a silicon carbide matrix around the carbon-carbon fiber structure.

Firms like Exothermics (Amherst, NH) use this process for missile and aerospace applications. The silicon carbide matrix structure provides an environmental barrier to oxidation during reentry into Earth’s atmosphere and improves the matrix’s temperature performance to approximately 1600°C (2910°F) in air.

Smaller production units were also developed for carbon-carbon work at temperatures from 2450°C and 2600°C (4440°F and 4710°F). The addition of dedicated water-cooled filtration traps and 10-μ particulate filters helps deal with the heavy off-gassing expected from processing of carbon-carbon materials.

In contrast to melt infiltration, chemical vapor infiltration drives gaseous reactants into the porous matrix where the gas reacts with the porous structure to form a dense matrix. The chemical vapor infiltration process is used to fabricate larger parts for hypersonic applications, such as rocket motors and missile components, and carbon-carbon aircraft brakes. Vertical top- and bottom-loading chemical vapor infiltration units like the example in Figure 6 can be used for these types of applications.


Figure 6. Series 4300 vacuum furnace for chemical vapor infiltration and graphitization. The furnace may be built in a top-loading or bottom-loading configuration; the unit scales from 52″ to 80″ (1,320 mm to 2,000 mm) in diameter and heights from 80″ up to 120″ (2.0 to 3.0 meters). | Image Credit: Centorr Vacuum Industries

In the chemical vapor infiltration process, gases, including hydrogen, methane, and propane, are fed into the furnace chamber at high flow rates and at temperatures approaching 1000°C–1100°C (1830°F–2010°F). The methane and propane gases break down and deposit carbon deep into the matrix of the carbon-carbon fibrous parts. These cycles can be very long, approaching seven to ten days, for the material to fully densify, and multiple cycles are usually necessary.

Low operating pressures require extremely large mechanical pumping systems with large vacuum blowers or boosters. These furnaces include water-cooled “tar” traps (with a heated stripping system) and large Dollinger particulate filters for handling the resin off-gas byproducts.

These furnaces are almost always induction heated, using multizone induction coils and large, thick-wall graphite susceptors for optimal temperature uniformity. The insulation design uses carbon black powder, which is economical and highly efficient for temperature reduction.

While more conventional rigid or flexible graphite board or felt materials can be used, Centorr’s experience has shown that the degree of infiltration of carbon resins over time will affect the density and porosity of the insulation pack (as it does the load material), causing degradation and densification of the insulation. The denser insulation results in high coil water temperatures, which compromises hot zone life. Specialized carbon black installation and removal equipment is required by the end-user to maintain the insulation efficiency of the furnace hot zone. Because gas flow in the furnace is critically important, special diffusor plates or plenums are used to uniformly direct gas flow across the entire geometry of the parts.

Once the advanced materials undergo chemical vapor infiltration, they are still composed of a carbon base material, which needs to be converted to a more orderly crystalline graphite structure to impart the durability and strength required in aerospace applications. To accomplish this conversion, the material needs to be heated at temperatures greater than 2300°C (4170°F), a process called graphitization.

The graphitization process employs similar furnace designs to the chemical vapor infiltration process, but the induction heating power supply is changed to the more conventional single zone coil, and the vacuum pumping systems are smaller with no tar traps needed. Load sizes of 3,000–5,000 lb. (1,360–2,268 kgs) are possible. Both the smaller and larger chemical vapor infiltration and graphitization units have large, water-cooled heat exchangers inline with large cooling fans, which reduce cooling times from ten or more days to less than 175 hours.


Figure 7. a) Series 3800 bottom-loading silicon carbide chemical vapor deposition furnace. b) Series 3800 chemical vapor deposition furnace hot zone with multizone control; 53″ diameter x 83″ height (1,350 mm x 2,108 mm) graphite hot zone furnace rated for 1600°C (2910°F) operation. | Image Credit: Centorr Vacuum Industries

A smaller graphitization unit was also developed in a 30″ diameter x 40″ height (76 mm x 1,000 mm) size rated to 2900°C (5250°F) maximum temperature in a vertical bottom-loading configuration for processing smaller parts in lower volumes for aerospace brakes.

The silicon carbide chemical vapor deposition units for laboratory applications discussed previously are also needed for production-size volumes (Figure 7). Due to tight temperature uniformity requirements, these units are multizone control with graphite hot zones constructed of rigid graphite board for process durability. The pumping systems can be either “dry” or “liquid ring” designs for processing the acidic off-gas materials. A post-exhaust chemical scrubber system is required to safely neutralize the hydrogen chloride off-gases.

Enabling the Next Generation of Aerospace Materials

The difficult design requirements of next-generation aerospace technologies will continue to push the existing limits of material performance. As characterization and development of new materials will be critical to the success of these aerospace programs, vacuum and controlled atmosphere furnaces will play an essential role in the production of such materials.

References

American Elements. n.d.a “Silicon Carbide Data Sheet.” https://www.americanelements.com/silicon-carbide-409-21-2.

American Elements. n.d.b “Zirconium Diboride Data Sheet.” https://www.americanelements.com/zirconium-diboride-12045-64-6.

Mesa, J. 2024. “What’s the Difference Between a Hypersonic Missile and ICBM?” Newsweek, November 21, 2024. https://www.newsweek.com/difference-between-icbm-irbm-missiles-1989780.

Smith, C. R. 2021. “Aerodynamic Heating in Hypersonic Flows.” Physics Today 74 (11): 66–67.

TomorrowDesk. 2025. “Hyperian Aerospace and the Dawn of Hypersonic Flight.” TomorrowDesk, March 29, 2025. https://tomorrowdesk.com/evolution/hyperian-aerospace-hypersonic-flight.

Heat Treat Today thanks the American Ceramic Society for allowing us to print this piece. This article was originally published in ACerS Bulletin, September 2025.

About The Author:

Scott K. Robinson
Product Manager of Ceramics and Powder Metallurgy
Centorr Vacuum Industries

Scott K. Robinson is product manager of ceramics and powder metallurgy at Centorr Vacuum Industries (Nashua, NH).

For more information: Contact Scott Robinson at srobinson@centorr.com.

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Ask The Heat Treat Doctor®: Why and How Do We Heat Treat Gears? Part Two

/ AEROSPACE HEAT TREAT TECHNICAL CONTENT, CARBURIZING TECHNICAL CONTENT, HARDENING TECHNICAL CONTENT, INDUCTION HEATING TECHNICAL CONTENT, OP-ED, QUENCHING TECHNICAL CONTENT, VACUUM FURNACES TECHNICAL CONTENT

Ask The Heat Treat Doctor® has returned to bring 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. In this installment, Dan Herring continues his discussion on gear heat treatment, exploring vacuum and induction hardening methods for gears — from low-pressure carburizing for advanced materials to single shot and tooth-by-tooth induction techniques — and how each can be matched to the specific demands of any gear application.

This informative piece was first released in Heat Treat Today’s March 2026 Annual Aerospace Heat Treating print edition.

In Part One of this discussion (Air & Atmospheres Heat Treating, February 2026), we discussed various gear types, materials, and how they can be atmosphere heat treated. This month, we are focusing on vacuum and induction heat treating methods. Let’s learn more.

Vacuum Heat Treatment Processing Methods

Table A. Advanced Materials Processed by LPC

Vacuum processing can be used for most of the atmosphere treatments mentioned in Part One including carburizing (Figure 1). Low pressure carburizing (LPC) is a proven technology and the choice for many advanced applications in aerospace, automotive, off-highway, and motorsports markets, as well as the development of carburizing cycles for high-performance materials (Table A).

Figure 1. Typical commercial heat treat load of gears for vacuum carburizing (Otto and Herring 2007) | Image Credit: Photo courtesy of Midwest Thermal-Vac
Figure 2. Pyrowear 675 – LPC – anneal – double normalize – harden – anneal – deep freeze – double temper | Image Credit: The HERRING GROUP, Inc.

The range of effective case depths for most of these grades can range up to 2.0–3.0 mm (0.080–0.120 inches) without significant sacrifice of microstructure (Figure 2). Furnace variables, such as temperature uniformity (± 3°C or ± 5°F), control of cycle parameters (boost/diffuse times, gas flow rate, pressure, hydrocarbon type) and surface carbon optimize the microstructure, producing case uniformities of ± 0.05 mm (± 0.002 inches). Where permitted, the range of carburizing temperatures now includes the use of high temperature (> 980°C, or 1800°F) techniques.

All these advanced materials required extensive development testing to produce custom designed recipes to optimize cycle parameters. Also, quenching methods (Otto and Herring 2002) have improved, allowing us to achieve desired core properties with quenching parameter selection (high-pressure gas or oil) for distortion-sensitive and distortion-prone part geometries (Otto and Herring 2005, 2008).

Induction Hardening Methods

Various methods of hardening via applied energy are used in manufacturing gears, including flame hardening, laser surface hardening, and induction hardening.

Of the various types of applied energy processing, induction hardening is the most common. Induction heating is a process that uses alternating electrical current that induces a magnetic field, causing the surface of the gear teeth to heat. The area is then quenched resulting in an increase in hardness within the heated area. This process is typically accomplished in a relatively short time. The final desired gear performance characteristics are determined not only by the hardness profile and stresses but also by the steel composition and prior microstructure. External spur and helical gears, bevel and worm gears, racks, and sprockets are commonly induction hardened. Typical gear steels include AISI/SAE grades 1050, 1060, 1144, 4140, 4150, 4350, 5150, and 8650.

Figure 3. Patterns produced by induction hardening (Rudnev 2000)

The hardness pattern produced by induction heating (Figure 3) is a function of the type and shape of inductor used, as well as the heating method. Quenching or rapidly cooling the workpiece can be accomplished by spray or submerged quench. The media typically used for the quench is a water-based polymer. The severity of this quenchant can be controlled by the polymer’s concentration. Cooling rates are usually somewhere in between what would be obtained from pure water and oil. In some unusual situations compressed air or nitrogen is used to quench the part.

The most common methods for hardening gears and sprockets are by single shot (Figure 4) or the tooth-by-tooth method (Figure 5). Single shot often requires large kW power supplies but results in short heat/quench times and higher production rates. This technique uses a circumferential copper inductor, which will harden the teeth from the tips downward.

Figure 4. Typical single shot induction hardening operation | Image Credit: Photo courtesy of Ajax-Tocco-Magnethermic
Figure 5. Tooth-by-tooth induction hardening of a helical gear | Image Credit: Photo courtesy of Ajax-Tocco-Magnethermic

The larger and heavier loaded gears (where pitting, spalling, tooth fatigue, and endurance are issues) need a hardness pattern that is more profiled like those produced by carburizing, which can be obtained by tooth-by-tooth hardening. This method is limited to gear tooth sizes with modulus 4.23–5.08 (6 or 5 DP) using frequencies from 2 to 10 kHz and about 2.54 (10 DP) using a range of 25 to 50 kHz.

The lower the frequency, the deeper the case depth. Tooth-by-tooth hardening is a slow process and usually reserved for gears and sprockets that are too large to single shot due to power constraints. The process involves heating the root area and side flanks simultaneously, while cooling each side of the adjacent tooth to prevent temper-back on the backside of each tooth. The induction system moves the coil at a pre-programmed rate along the length of the gear. The coil progressively heats the entire length of the gear segment while a quench follower immediately cools the previously heated area. The distance from the coil to the tooth is known as coupling or air gap. Any changes in this distance can yield variation in case depth, hardness, and tooth distortion. The gear is indexed after each tooth has been hardened, often skipping a tooth. This requires at least two full revolutions in the process to complete the hardening of all teeth. Straight, spur, and helical gears up to 5.5 m (210 inches) weighing 6,800 kg (15,000 lb) have been processed with this method. The entire process yields a repeatable soft tip of the tooth with hard root and flank. In other applications, the tip and both flanks can be hardened simultaneously and yield a soft root.

In Summary

Today’s design engineer has the good fortune of being able to choose from a number of heat treatment technologies for any given type of gear material and design. When selecting a gear hardening method, it is essential to specify not only the desired mechanical and metallurgical properties, but the critical dimensions that must be held and even the desired stress state of the gears themselves. The secret to success is understanding the advantages and limitations of each technology and taking these into consideration when determining the overall cost of gear manufacturing.

References

Herring, Daniel H. 2004a. “Gear Heat Treatment: The Influence of Materials and Geometry.” Gear Technology, March/April.

Herring, Daniel H. 2004b. “Reducing Distortion in Heat-Treated Gears.” Gear Solutions, June.

Herring, Daniel H. 2007a. “Oil Quenching Technologies for Gears.” With Steven D. Balme. Gear Solutions, July.

Herring, Daniel H. 2007b. “Heat Treating Heavy Duty Gears.” With Gerald D. Lindell. Gear Solutions, October.

Herring, Daniel H. 2012–2016. Vacuum Heat Treatment. Vols. 1–2. BNP Media Group.

Herring, Daniel H. 2014–2015. Atmosphere Heat Treatment. Vols. 1–2. BNP Media Group.

Herring, Daniel H., Gerald D. Lindell, D. J. Breuer, and B. Matlock. 2001. “Atmosphere vs. Vacuum Carburizing.” Heat Treating Progress, November.

Herring, Daniel H., Gerald D. Lindell, D. J. Breuer, and B. Matlock. 2002. “An Evaluation of Atmosphere and Vacuum Carburizing Methods for the Heat Treatment of Gears.” In Off-Highway Conference Proceedings. SAE International.

Otto, Frederick J., and Daniel H. Herring. 2002a. “Gear Heat Treatment: Today and Tomorrow, Part 1.” Heat Treating Progress, June.

Otto, Frederick J., and Daniel H. Herring. 2002b. “Gear Heat Treatment: Today and Tomorrow, Part 2.” Heat Treating Progress, July/August.

Otto, Frederick J., and Daniel H. Herring. 2005. “Vacuum Carburizing of Aerospace and Automotive Materials.” Heat Treating Progress, January/February.

Otto, Frederick J., and Daniel H. Herring. 2007. “Advancements in Precision Carburizing of Aerospace and Motorsports Materials.” Heat Treating Progress, May/June.

Otto, Frederick J., and Daniel H. Herring. 2008. “Improvements in Dimensional Control of Heat Treated Gears.” Gear Solutions, June.

Rudnev, V. 2000. “Gear Heat Treating by Induction.” Gear Technology, March/April.

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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Heat Treatment of Carbon and Graphite-Based Materials for Space Travel and Exploration

/ AEROSPACE HEAT TREAT TECHNICAL CONTENT, VACUUM FURNACES TECHNICAL CONTENT

Carbon and graphite-based materials are among the few engineered materials capable of withstanding the extreme thermal, mechanical, and environmental demands of space travel. In this Technical Tuesday installment, Kimberly Thompson, technology manager at Morgan Advanced Materials, examines how carefully controlled heat treatment directly governs the structure, purity, and performance of these materials and emphasizes the importance of furnace design, atmosphere control, and temperature precision required to achieve reliable properties for aerospace and space exploration applications.

This informative piece was first released in Heat Treat Today’s March 2026 Annual Aerospace Heat Treating print edition.

Space travel presents one of the most extreme operating environments encountered by engineered materials. Launch, orbital operation, atmospheric reentry, and deep space exposure all impose combinations of extreme temperature, rapid thermal cycling, oxidative attack, mechanical stress, and radiation. Among the limited class of materials capable of performing in these challenging conditions, carbon and graphite-based materials have played a critical role for decades, continuing to enable and innovate modern space exploration.

From carbon ablatives, which play a crucial role in heat shields and propulsion systems, to structural graphite components and ultra-pure graphitic elements, carbon materials are uniquely suited to survive and perform in extreme temperature regimes that exceed the limits of metals and ceramics. The performance of these graphite/graphite-like materials is directly linked to the heat treatment (aka graphitization) and processing steps used during their manufacture. The relationship between processing conditions and final product performance is driven by the technical foundations for heat treating carbon and graphite materials for space travel through the conversion, graphitization, and purification steps.

Carbon Materials in Space Applications

Carbon-based materials, such as those produced by the Performance Carbon division of Morgan Advanced Materials (see Figures 1-3), have a long history of being utilized in spaceflight systems due to their exceptional thermal stability, low density and mass, and resistance to thermal shock. Common applications include:

  • Ablative thermal protection systems for atmospheric re-entry
  • Nozzle throats and rocket motor components
  • High temperature insulation and support
  • Structural graphite parts
  • Ultra-pure graphitic components for sensitive electronic or propulsion systems

The performance outcomes required in these applications are diverse but share common demands: survivability at extreme temperature exceeding 2000°C (3630°F) and down to -270°C (-450°F), predictable thermal behavior, low outgassing, and controlled erosion or sublimation rates. Achieving these characteristics relies heavily on heat treatment processing conducted through both low and high temperatures.

Figure 1. Carbon cloth | Image Credit: Morgan Advanced Materials
Figure 2. Felted rayon billets | Image Credit: Morgan Advanced Materials
Figure 3. Rayon felt | Image Credit: Morgan Advanced Materials

As the material is heat treated and temperatures increase, the carbon structure will undergo progressive stabilization. Precursor conversion or pre-carbonization will occur during low temperature thermal processing. Fundamental transformation will occur as the disordered carbon structure reorganizes into graphitic planes through realignment of aromatic carbon layers. The planes become progressively ordered in the presence of elevated temperatures, increasing crystallographic alignment. The transition from carbon to graphite is gradual and highly reliant on heat treatment process capability to maintain thermal uniformity throughout all process stages.

The extent of graphitization is typically tailored to meet specific application requirements, as carbon and graphite structures each offer distinct performance advantages. In certain applications, a predominately carbon structure is preferred due to its higher bulk density and superior mechanical strength as compared to graphite. These characteristics can be advantageous in space applications where structural integrity, load bearing capability, or erosion resistance under mechanical stress are primary concerns. However, carbon materials generally exhibit slightly lower carbon yield and may experience higher erosion or mass loss when exposed to extreme thermal flux or oxidative stress.

In contrast, materials processed to a graphitic structure offer enhanced thermal stability at elevated temperatures, improved resistance to thermal shock, and reduced impurity content due to high temperature volatilization of contamination. Graphite materials typically demonstrate superior performance in applications requiring sustained exposure to ultra high temperature or rapid thermal cycling. This benefit, however, is often accompanied by lower density and reduced mechanical strength relative to their carbon counterparts, which can limit their use in mechanically demanding roles.

Ultimately, the selection of a carbon- or graphite-based structure involves balancing thermal performance, mechanical requirements, erosion behavior, and environmental exposure. Heat treatment parameters must be carefully engineered to achieve the desired degree of structural ordering, ensuring that the final material delivers optimal performance for its intended spaceflight application.

Low Temperature Thermal Processing

Most engineered carbon precursors, such as cellulose, phenolic resin, acrylic (polyacrylonitrile), or pitch-based materials, require conversion into carbon through a sequence of controlled thermal processes. The first conversion process is considered low temperature in terms of graphite processing. During this process, hydrogen, oxygen, and nitrogen content decreases, volatile species are driven off, and the aromatic carbon structures begin to form. The thermal processing profile through this low temperature conversion is critical. Careful control of heat treatment parameters, tailored to the material system, supports uniform carbon conversion and minimizes defects as the foundational microstructure is established.

At these processing temperatures, a wide range of conventional heat treatment equipment can be effectively used. Because the operating temperatures remain below the limits of most metallic alloys, furnaces equipped with metal-based heating elements, structural components, and containment systems are generally suitable for this phase of processing. Additionally, these furnaces may be configured as batch or continuous systems, depending on part geometry, production volume, and process control requirements. Heat input is achieved through established industrial thermal processing approaches, with system selection guided by requirements for temperature uniformity, process control, and operational considerations. Regardless of the configuration, the selected furnace must be capable of maintaining stable inert or reducing atmospheres to prevent oxidation of the carbon precursor during thermal decomposition.

Successful low temperature processing demands a strong foundational understanding of carbonization mechanisms combined with sound materials science principles. As organic precursors are heated, complex chemical reactions occur that result in the formation of increasingly ordered carbon structures. The heating rate and soak durations must be carefully engineered to accommodate these reactions while minimizing internal stresses, distortion, or excessive porosity. Improper ramp rates or insufficient soak times can result in non-uniform shrinkage and irreversible defects that propagate through later processing stages.

Equally critical is the furnace’s ability to execute the programmed temperature profile with a high degree of precision and repeatability. Accurate control of heating ramps, dwell temperatures, and cooling rates is essential, as even modest deviations can alter the evolving microstructure of the material. Temperature overshoot, uncontrolled gradients, or localized hot spots can lead to uneven carbon yield, variations in density, and inconsistent mechanical or thermal properties in the final product. Consistency of temperature accuracy within the furnace ensures that the entire product load processes uniformly, reducing variation in the material to allow for uncompromised performance in demanding aerospace applications.

High Temperature Thermal Processing

Materials that have completed precursor conversion or pre-carbonization are subsequently subjected to high temperature thermal processing to complete carbonization or to initiate and advance graphitization, thereby establishing the final material structure and properties. Although the carbon microstructure continues to evolve significantly during this stage, the material experiences minimal additional mass loss, shrinkage, or chemical decomposition compared to earlier processing stages. Most volatile species have already been removed, resulting in a comparatively stable structure that is less susceptible to distortion, cracking, or dimensional change. As a result, parts processed in this temperature regime typically exhibit improved dimensional stability and reduced sensitivity to heating rates when compared to low-temperature carbonization operations.

High-temperature processing can be conducted at temperatures well above the lower temperature processing. At these elevated temperatures, the available furnace technologies become significantly limited. Conventional metal or ceramic based furnace systems are no longer suitable due to material degradation, contamination risk, and structural instability under these conditions. Instead, furnaces designed for high-temperature carbon and graphite processing are typically induction or resistance (i.e., vacuum furnace) heated and constructed primarily from graphite-based components.

These furnace systems are specifically engineered to withstand extreme temperatures while maintaining thermal uniformity and chemical compatibility with the carbon materials being processed. The use of graphite heating elements, insulation, and structural components minimizes contamination and allows operation in inert or controlled atmospheres required for carbon and graphite processing.

As relatively little chemical decomposition occurs during this phase, high-temperature processing cycles can often be completed more rapidly than low-temperature carbonization cycles. Additionally, moderate temperature variations within the furnace are less likely to produce significant variability in final material properties. However, precise temperature control remains critical, as the peak temperature achieved during processing largely determines the degree of carbonization or graphitization and, consequently, the final microstructure and performance characteristics of the material.

Continuous monitoring and accurate measurement of operating temperatures are therefore essential. Even small deviations in maximum temperature can lead to meaningful differences in crystallinity, density, thermal conductivity, and mechanical behavior. For space applications, where consistency and reliability are paramount, ensuring that each component reaches the intended peak temperature is a defining requirement of high-temperature thermal processing. As space missions continue to demand materials capable of performing in the most extreme environments, advanced heat treatment remains a critical enabler of reliability and innovation.

About The Author:

Kimberly Thompson
Technology Manager
Morgan Advanced Materials

Kimberly Thompson holds a bachelor’s degree in chemical engineering from Purdue University and a master’s degree in materials engineering from Auburn University. With nearly nine years with Morgan Advanced Materials, she currently serves as technology manager leading new product development and has spent six years as the technical resource for rayon-based carbon and graphite materials supporting space industry applications.

For more information: Contact Kimberly Thompson at Kimberly.Thompson@morganplc.com.

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IN 718 Part 2: Heat Treatment

/ AEROSPACE HEAT TREAT TECHNICAL CONTENT, ANNEALING TECHNICAL CONTENT, HIPING TECHNICAL CONTENT, VACUUM FURNACES TECHNICAL CONTENT

Today’s Technical Tuesday highlights the second installment in a multi-part series by Nikolai Alexander and The Heat Treat Doctor® Daniel H. Herring, diving into the controlled heat treatment strategies required to unlock IN 718’s exceptional high-temperature strength, toughness, and corrosion resistance. From solution annealing and duplex aging to hot isostatic pressing and additive manufacturing considerations, the authors explore how precise process control and equipment selection directly shape microstructure and performance in critical applications.

This informative piece is from Heat Treat Today’s March 2026 Annual Aerospace Heat Treating print edition. For part 1 on the history, production, and general applications, read Heat Treat Today’s February 2026 Annual Air & Atmosphere Heat Treating print edition.

Introduction

IN 718 was developed for and is extensively used in the aerospace industry. Today, the superalloy and its modifications are heavily relied upon, including IN 718Plus® (US Patent No. 6.730.264 B2), which is designed for operating service temperature to 705°C (1300°F), approximately 55°C (100°F) above that of IN 718. (IN 718Plus will be the subject of a future article by the authors). This article reviews the heat treatment of IN 718 and the need to control both equipment and process variability. Also discussed is the method of additive manufacturing (AM) to produce component parts and the heat treat challenges it poses, including the need to HIP (hot isostatically press) the material to achieve maximum property benefits.

Heat Treatment of IN 718

Figure 1. Typical vacuum furnace used for heat treating IN 718 | Image Credit: Solar Manufacturing

IN 718 is typically heat treated in a vacuum furnace given that it is a sensitive alloy and easily oxidized. Processing in an all-metal shielded furnace (Figure 1) offers advantages for keeping the parts bright after the aging process, without the need to wrap them.

Graphite-lined vacuum furnaces, often with molybdenum heating elements, can also be used provided appropriate precautions are taken. The furnace must be extremely leak tight with a rate of rise under 5 microns Hg per hour. Processing in vacuum is typically done in the 10⁻⁵ torr range. Argon as a partial pressure or cooling gas is necessary to avoid nitriding or oxidation. An alternative, albeit older technology, approach is the use of a vacuum-purged argon atmosphere box furnace with a retort.

From a metallurgical perspective, the amount, morphology, and distribution of the delta (δ) phase have a great influence on the properties of IN 718. During heat treatment, delta phase is extremely important for optimizing mechanical properties, particularly at high temperatures to control migration and precipitation in IN 718. The delta phase inhibits grain growth (by pinning the grain boundaries) and enhances creep and fatigue performance. However, excessive or poorly controlled precipitation is detrimental to other properties like ductility and fracture toughness.

Optimization of delta phase distribution includes selecting the proper solutionizing temperature, between 980–1040°C (1800–1900°F) depending primarily on nickel content, where the delta phase is stable (and thus precipitates out). Thermomechanical working can also achieve this effect by forming more globular-shaped particles rather than acicular (needle-like) ones (Guan, et al. 2023).

There are a number of heat treatments that can be performed on IN 718, including stress relief, homogenizing, solution annealing, precipitation hardening (aka aging), and HIP.

Stress Relief

Stress relief is typically performed at the mill and is a compromise between the amount of residual stress one would like to remove and the possibly harmful effects to both high temperature properties and corrosion resistance. For wrought alloys, stress relief at full annealing temperature is recommended since intermediate temperatures might cause aging. Hold times are one hour per inch of section thickness. For castings, stress relief is especially important when dealing with complex shapes, which may be prone to cracking in subsequent operations or when dimensional control is important.

Homogenization

Homogenization heat treatment is applied to IN 718 for the uniform distribution of alloying elements and dissolution of detrimental phases after its processing through casting and additive manufacturing (AM) routes. There is a definite relationship between laves phase fraction (i.e., the brittle intermetallic compound formed due to niobium segregation during solidification) and homogenization time at various temperatures 1140–1170°C (2085–2140°F). With an increase in homogenization temperature, the time required for dissolution of laves phase and reduction in laves phase fraction reduces drastically. Also, at a given temperature the reduction in laves phase fraction has been shown to occur with the increase of time (Eliasen and Somers 2010).

Full Annealing

Figure 2. Full annealing of IN 718 alloy bars | Image Credit: Solar Atmospheres, Inc.

The process of full annealing involves complete recrystallization and dilution of all or most of the secondary phases to reach maximum softness (Figure 2).

The process is typically run at 955°C (1750°F) holding one hour per inch of cross-sectional area. If welding is to be performed on the component, annealing should be performed immediately after the welding operation. It is noteworthy that niobium additions help overcome cracking problems during welding.

Solution Annealing

Solution annealing (aka solution heat treating) is designed to dissolve secondary phases to prepare the alloy for age hardening and produce maximum corrosion resistance. An added benefit is homogenization of the microstructure.

Figure 3. Standard heat treatment cycle of IN 718 | Image Credit: Polasani and Dabhade 2024

A typical heat treatment of IN 718 involves a two-step process — solution heat treating and then age hardening — to control the mechanical property response of the material (Figure 3).

For bar stock, a typical cycle might involve solution annealing at 955°C (1750°F) followed by a 2-bar quench under argon or nitrogen (which can be used if post machining will be performed). This is followed by duplex aging at 730°C (1350°F) for eight hours followed by a vacuum or rapid cool to avoid surface reactions (such as oxidation) and (depending on whether further precipitation is needed) to 650°C (1150°F) and another hold for eight hours followed by a gas fan quench.

Solution annealing at 925–1010°C (1700–1850°F) with its corresponding aging treatment is considered the optimum heat treatment for IN 718, where a combination of rupture life, notch rupture life, and rupture ductility is of greatest concern. The highest room-temperature tensile and yield strengths are also associated with this treatment. In addition, because of the fine grain developed, it produces the highest fatigue strength (Herring 2019).

By contrast, solution annealing at 1040–1065°C (1900–1950°F) with its corresponding aging treatment is the treatment preferred in tensile-limited applications because it produces the best transverse ductility in heavy sections, impact strength, and low-temperature notch tensile strength. However, this treatment tends to produce notch brittleness in stress rupture (Herring 2019).

Aging/Duplex Aging

Figure 4. Duplex aging of IN 718 land-based turbine rods | Image Credit: Solar Atmospheres, Inc.

The aging process is designed to strengthen the material, forming precipitates from the supersaturated solid solution mastic from the solution annealing step.

Duplex aging (Figure 4) involves a two-step heat treatment process and on IN 718 is performed around 730°C (1350°F) for eight hours followed by a vacuum cool or in some cases a rapid cool to avoid surface reactions (such as oxidation) and (depending on whether further precipitation is needed) down to 620°C (1150°F) and another hold for eight hours. This is followed by a gas fan quench. The first soak temperature is intended to initiate precipitation of phases influencing strength and hardness properties. The second soak temperature further refines the microstructure and optimizes the material’s properties based on the phases developed in the initial aging and cooling stages.

Hot Isostatic Pressing

Figure 5. Typical HIP furnace capable of high temperature/pressure | Image Credit: AVS Inc.

Hot isostatic pressing (HIP) combines high pressure and high temperature to influence the density and microstructure of IN 718 (Figure 5). It is critically important to improve the mechanical strength of shape cast and additive manufactured components to homogenize the as-built microstructure and minimize variation in mechanical properties. It helps to eliminate residual stresses, close pores, close cracks and ensures the material is properly fused (Shipley 2023).

For example, it has been reported (Lee, et al. 2006) that four hours at 2155°F (1180°C) under a pressure of 25.5 ksi (175 MPa) is optimal to improve the microstructure (grain size and segregation) along with tensile properties of IN 718 castings.

Future Outlook

Additive manufacturing (AM) of IN 718 (and superalloys in general) is becoming an increasingly important method for component part manufacturing. It allows complex 3D shapes to be formed without the difficulties inherent in casting, forming, and machining of these alloys.

Electron beam-powder bed fusion (E-PBF) and laser-beam powder bed fusion (L-PBF) have shown great promise for processing IN 718 and other nickel-based superalloys. An absolutely necessary, if not critical, step in the process is post-HIP to heal cracks and homogenize the microstructure.

Heat treating will continue to play an important role in enhancing the properties of IN 718. It will be necessary to update the standard heat treatment requirements (e.g., AMS5662 and AMS5663) to incorporate powder metallurgy (PM) and AM technologies to optimize properties for components made by these methods.

More investigation is needed to optimize solutionizing and aging temperatures for modified IN 718 chemistries. For example, the effect of the cooling rate after aging treatments on the precipitate size and morphology and subsequent mechanical properties of the alloy must be explored in more detail (Eliasen and Somers 2010). And from a heat treatment perspective there is interest in case hardening (nitriding, low-temperature carburizing) of IN 718 (Sharghi-Moshtaghin, et al. 2010, Eliasen and Somers 2010).

Finally, AM processes rely on layer-upon-layer melting. As such, modeling, sensor technology, process temperature monitoring and control of surface displacement improve the build. Emerging trends suggest that the integration of machine learning and artificial intelligence for real-time quality control and process optimization will be a key part of the manufacturing strategy moving forward (Babu, et al. 2018).

References

Akca, Enes, and Gursel, Ali. 2015. “A Review on Superalloys and IN718 Nickel-Based INCONEL Superalloy.” Periodicals of Engineering and Natural Sciences 3 (1): 15–27.

ASM International. 2016. ASM Handbook, Volume 4E: Heat Treating of Nonferrous Alloys. ASM International.

Babu, S. S., N. Raghavan, J. Raplee, S. J. Foster, C. Frederick, M. Haines, R. Dinwiddie, M. K. Kirka, A. Plotkowski, Y. Lee, and R. R. Dehoff. 2018. “Additive Manufacturing of Nickel Superalloys: Opportunities for Innovation and Challenges Related to Qualification.” The Minerals, Metals & Materials Society and ASM International: 3764–3780.

Bradley, Elihu F., ed. 1988. Superalloys: A Technical Guide. ASM International.

del Bosque, Antonio, Fernández-Arias, Pablo, and Vergara, Diego. 2025. “Advances in the Additive Manufacturing of Superalloys.” Journal of Manufacturing and Materials Processing 9 (215): 1–31.

Chandler, Harry, ed. 1996. Heat Treater’s Guide: Practices and Procedures for Nonferrous Alloys. ASM International.

Croft Systems. n.d. “The Difference between a Wellhead & Christmas Tree.” https://www.croftsystems.net/oil-gas-blog/the-difference-between-a-wellhead-christmas-tree/.

Decker, R. F. 2006. “The Evolution of Wrought Age-Hardenable Superalloy.” Journal of The Minerals, Metals & Materials Society, September: 32–36.

Eliasen, K. M., T. L. Christiansen, and M. A. J. Somers. 2010. “Low-Temperature Gaseous Nitriding of Ni-Based Superalloys.” Surface Engineering 26 (4): 248–255.

Guan, Hao, Wenxiang Jiang, Junxia Lu, Yuefie Zhang, and Ze Zhang. 2023. “Precipitation of δ Phase in Inconel 718 Superalloy: The Role of Grain Boundary and Plastic Deformation.” Materials Today Communications 36 (August).

Herring, Daniel H. 2011. “Stress Corrosion Cracking.” Industrial Heating, October: 22–24.

Herring, Daniel H. 2012. Vacuum Heat Treating: Principles, Practices, Applications. BNP Media II, LLC.

Herring, Daniel H. 2019. “The Heat Treatment of Inconel 718.” Industrial Heating, June: 12–14.

Lee, Gang Ho, Ang Ho, Minha Park, Byoungkoo Kim, Jong Bae Jeon, Sanghoon Noh, and Byung Jun Kim. 2023. “Evaluation of Precipitation Phase and Mechanical Properties According to Aging Heat Treatment Temperature of Inconel 718.” Journal of Materials Research and Technology 27 (Nov–Dec): 4157–4168. https://doi.org/10.1016/j.jmrt.2023.10.196.

Lee, Shin-Chin, Shih-Hsien Chang, Tzu-Piao Tang, Hsin-Hung Ho, and Jhewn-Kuang Chen. 2006. “Improvements in the Microstructure and Tensile Properties of Inconel 718 Superalloy by HIP Treatment.” Materials Transactions 47 (11): 2877–2881.

Loria, Edward A. 1988. “The Status and Prospects of Alloy 718.” Journal of Materials, July: 36–41.

Polasani, Ajay, and Vikram V. Dabhade. 2024. “Heat Treatments of Inconel 718 Nickel-Based Superalloy: A Review.” Metals and Materials International: 1204–1231.

Sharghi-Moshtaghin, Reza, Harold Kahn, Yindong Ge, Xiaoting Gu, Farrel J. Martin, Paul M. Natishan, Arrell J. Martin, Roy J. Rayne, Gary M. Michal, Frank Ernst, and Arthur H. Heuer. 2010. “Low-Temperature Carburization of the Ni-Base Superalloy IN718: Improvements in Surface Hardness and Crevice Corrosion Resistance.” Metallurgical and Materials Transactions A 41A (August): 2022–2032.

Shipley, Jim. 2023. “Hot Isostatic Pressing and AM: How to Improve Product Quality and Productivity for Critical Applications.” Metal AM 9 (3).

U.S. Patent No. 3,046,108.

Acknowledgments: This paper would not have been possible without discussions, guidance and contributions from a number of individuals in both the heat treat industry and academia.

Special Note: Inconel® is a registered trademark of Special Metals Corporation group of companies.

About the Authors:

Dan Herring
“The Heat Treat Doctor®”
The HERRING GROUP

Dan Herring, who is most well known as The Heat Treat Doctor®, has been in the industry for over 50 years. He spent the first 25 years in heat treating prior to launching his consulting business, The HERRING GROUP, in 1995. His vast experience in the field includes materials science, engineering, metallurgy, equipment design, process and application specialist, and new product research. He is the author of six books and over 700 technical articles.

Nikolai Alexander Hurley
Intern
The Heat Treat Doctor®

Nikolai Alexander Hurley is a young academic, interning with The Heat Treat Doctor®.

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

IN 718 Part 2: Heat Treatment Read More »

IN 718 Part 1: History, Applications, and Production

/ ENERGY HEAT TREAT TECHNICAL CONTENT, FOUNDRY CASTING TECHNICAL CONTENT, MANUFACTURING HEAT TREAT TECH, VACUUM FURNACES TECHNICAL CONTENT

Today’s Technical Tuesday highlights this first installment in a multi-part series by Nikolai Alexander and The Heat Treat Doctor® Daniel H. Herring, which introduces Inconel® Alloy 718, one of the most widely used nickel-based superalloys, tracing its history, applications, and production fundamentals. Understanding why this alloy performs so well in extreme environments is critical as manufacturers consider material choices available for demanding components, especially alloys more typically sourced outside of one’s own industry. As demanding performance capabilities are being required of new engineered solutions, selecting the right alloy becomes a strategic decision to meet the need for higher temperatures, pressures, and corrosive environments.

This informative piece is from Heat Treat Today’s February 2026 Annual Air & Atmosphere Heat Treating print edition.

History

Inconel® Alloy 718 (IN 718) is a nickel-iron base superalloy known for its exceptional strength, resistance to high temperatures and ability to withstand harsh environments, where oxidation, creep, and corrosion resistance are paramount. The alloy was created by Dr. Herbert L. Eiselstein, who began his research in 1958, culminating in a patent assigned to The International Nickel Company in 1962 (U.S. Patent No. 3,046,108). In the many years since its creation, IN 718 remains the most widely used of all superalloys due to its availability in both wrought and cast products with high strength and stress-rupture life up to 650°C (1200°F), good hot working characteristics, castability, weldability, and cost effectiveness — all in an alloy with nominally 18% iron! The alloy’s superior performance is due in large part to its unique strengthening mechanisms.

There are different classifications of a superalloy, all based around the predominant metal present in the alloy. These categories include (Akca and Gursel 2015):

  • Nickel-based
  • Iron-based
  • Cobalt-based

The microstructural design makes IN 718 one of the best alloys for service applications below 650°C (1200°F) (Loria 1988, Herring 2011). It is widely used in extreme environments where components are subjected to high temperature, pressure, and/or mechanical loads. When heated, IN 718 forms a thick, stable, passivating oxide layer that protects the surface from further attack.

The alloy retains strength over a wide temperature range, making it attractive for high-temperature applications where materials like aluminum and steel would fail due to creep caused by thermally induced crystal vacancies. Inconel’s high-temperature strength is developed through heat treatment by solutionizing and precipitation hardening.

IN 718 is an alloy used around the world, but you might know it better by one of a variety of trade names (see sidebar).

The alloy has been modified numerous times to extend its operating temperature and service life. The alloy is readily available in all of these modified variations, each having slight differences in chemistry, cast and wrought processing methods, and heat treatments.

Applications

There is a wide variety of IN 718 applications across many industries, including aerospace, nuclear, oil and gas, automotive, motorsport, chemical processing, non-nuclear power generation, medical, tooling and molds, and fire protection systems.

In the automotive and motorsport industry, IN 718 is used for turbocharger rotors, exhaust manifolds, and valve springs in high-performance engines, such as those found in Formula 1 or the 24 Hours of Le Mans race cars. Naval warships are also purported to use IN 718 for components in their nuclear reactors (Table A).

Table A. Possible Uses of IN 718 in Naval Warship Nuclear Reactors
Table B. Oil & Gas Industry Use Examples for IN 718
Figure 1. A “Christmas tree”: the complex assembly of valves, gauges, and controls installed at the surface of a completed oil or gas well which has the primary function of regulating and controlling the flow of oil from the well. | Image Credit: Croft Systems

Perhaps surprisingly, IN 718 is also widely used in the oil and gas industry, which in addition to its many other benefits has remarkable resistance to sulfide and chlorine stress corrosion cracking at both high and low temperatures (Table B). Stress corrosion cracking is a failure mechanism that is caused by a combination of environment, a susceptible material, and the presence of tensile stress. Oil and gas applications like downhole tools, wellhead components, and subsea equipment benefit from IN 718’s other valuable properties as well, some of which include:

  • High strength and toughness at temperatures up to 700°C (1290°F)
  • Excellent resistance to pitting, crevice corrosion, and stress corrosion cracking
  • Sustained strength in hydrogen sulfide (H2S) and CO2-rich environments
  • Good weldability and fabrication

Continuous innovations in processing and material chemistry have enhanced superalloy properties resulting in the extension of its use into other industries, such as the energy and more conventional transportation sectors (Loria 1988).

Production Methods

IN 718 is available in cast and wrought alloy form and follows a stringent production process (Figure 2). Basic melt practices are used, such as vacuum induction melting (VIM), vacuum arc remelting (VAR), and electro-slag remelting (ESR).

Figure 2. Flow diagram of processes widely used to produce superalloys (Data reference: Akca and Gursel 2015)

VIM

The VIM process produces liquid metal under vacuum in an induction-heated crucible. It is used as a primary melting step in the route to producing wrought and cast products. Before being melted, the raw material can be refined and purified, and its composition can be controlled. VIM has been widely used in the manufacture of all types of superalloys, which must be melted under vacuum or in an inert gas atmosphere because of their reactivity with atmospheric oxygen and nitrogen.

VAR

The VAR process, a secondary melting technique, converts VIM-processed electrodes into ingots whose chemical and physical homogeneity have been significantly improved. In this process, a stub is welded to one end of an electrode, which is then suspended over a water-cooled copper crucible. Next, an arc is struck between the end of the electrode and the crucible bottom. Maintaining the arc generates the heat required to melt the electrode, which drips into the crucible and can subsequently be poured into molds. Many inclusions can be removed by flotation or chemical and physical processes before the molten material solidifies.

ESR

The ESR process, another secondary melting technique, is similar to the VAR process, but with notable differences. Remelting does not occur by striking an arc under vacuum. Instead, an ingot is built up in a water-cooled mold by melting a consumable electrode that is immersed in a slag, which is superheated by means of resistance heating. Rather than operating in a vacuum, the process is conducted in air under the molten slag. During melting, metal droplets fall through the molten slag, and chemical reactions reduce sulfur and nonmetallic inclusions. Both ESR and VAR processes allow directional solidification of an ingot from bottom to top, yielding high density and homogeneity in its macrostructure, as well as an absence of segregation and shrinkage cavities.

Casting Methods

IN 718 can also be produced by several casting methods. The most common of these are investment casting and (vacuum) die casting:

  • Investment casting: This process involves creating a wax pattern, coating it with a ceramic shell, melting out the wax, and then pouring molten IN 718 into the ceramic mold.
  • Vacuum die casting: This method uses a vacuum to fill the mold, resulting in a refined grain structure, minimal porosity, and good dimensional reproducibility, making it suitable for components like airfoils.
  • Sand casting: This method is far less common due to its inherent limitations in precision and surface finish, but the technology has been used for large castings.

A Metallurgical Perspective: The Role of Gamma Prime and Double Prime

IN 718 is a precipitation hardening superalloy. Its principle strengthening phases are gamma prime (γ′) or Ni3Al and gamma double prime (γ″) or Ni3Nb. The relationship between these precipitates (and others) and the gamma (γ) nickel matrix is critically important. For example, the coherency strain (i.e., the elastic deformation that occurs between two phases when their lattice structures do not perfectly match) is due to the fact that γ′ is face-centered cubic and γ″ is body centered tetragonal. In the case of IN 718, these strengthening effects are influenced more by γ″ than γ′ (ASM International 2016, Lee et al. 2023).

In addition, IN 718 has a natural tendency to precipitate rapidly by homogeneous nucleation in the noncompressible γ matrix. Depending on chemistry, γ′ volume percentage can vary over a wide range (3%–65%). Practically speaking, creep strength is proportional to volume percent over this range at temperatures between 700–980°C (1290–1800°F). As a result, the ratio of titanium to niobium/aluminum is key to hardening. High ratios imparted by niobium assure high strength at intermediate service temperatures around 600°C (1110°F). For higher service temperatures, higher aluminum content and molybdenum additions minimize the γ and γ′ mismatch, thus contributing to more stable alloys (Decker 2006, Guan et al. 2023).

Finally, the size and shape of these precipitates is important; larger precipitates enhance the strengthening effect. Key to the formation of these two precipitates is the aging treatment temperature, time, and alloy composition. According to existing research, higher aging treatment temperatures and longer times can lead to an increased amount of γ″ while extended aging coarsens the γ′ and γ″ particles, potentially leading to a reduction in strength and creep resistance. Furthermore, the composition ratios of Al, Ti, and Nb in the alloy influence the shapes of γ′ and γ″ precipitates, forming so-called co-precipitates that also affect the properties (Table C).

*SS = solid solution; + = enhancement; — = negative effect
Table C. Effect of Various Alloying Elements (Data Reference: Decker 2006)

The highest strength and hardness, coupled with reduced impact toughness, have been observed after heat treatment at 718°C (1325°F), due to an increase in the size and quantity of γ′ and γ″ precipitates.

In addition, as a result of surface analysis of Charpy bars, intergranular fracture occurs due to abundant small-sized precipitates formed within the boundary. In the case of the Charpy impact test, the absorbed energy decreases as the aging temperature increases. The formation of carbide, γ′ and γ″ precipitates can reduce the impact toughness of materials because precipitates may cause more obstacles to dislocation movement and promote crack initiation and propagation (Lee et al. 2023).

This article’s discussion continues in Heat Treat Today’s Annual Aerospace Heat Treat (March 2026) print edition to address heat treatment methods for this superalloy.

References

Akca, Enes, and Gursel, Ali. 2015. “A Review on Superalloys and IN718 Nickel-Based INCONEL Superalloy.” Periodicals of Engineering and Natural Sciences 3 (1): 15–27.

ASM International. 2016. ASM Handbook, Volume 4E: Heat Treating of Nonferrous Alloys. ASM International.

Babu, S. S., N. Raghavan, J. Raplee, S. J. Foster, C. Frederick, M. Haines, R. Dinwiddie, M. K. Kirka, A. Plotkowski, Y. Lee, and R. R. Dehoff. 2018. “Additive Manufacturing of Nickel Superalloys: Opportunities for Innovation and Challenges Related to Qualification.” The Minerals, Metals & Materials Society and ASM International: 3764–3780.

Bradley, Elihu F., ed. 1988. Superalloys: A Technical Guide. ASM International.

Chandler, Harry, ed. 1996. Heat Treater’s Guide: Practices and Procedures for Nonferrous Alloys. ASM International.

Croft Systems. n.d. “The Difference between a Wellhead & Christmas Tree.” https://www.croftsystems.net/oil-gas-blog/the-difference-between-a-wellhead-christmas-tree/

Decker, R. F. 2006. “The Evolution of Wrought Age-Hardenable Superalloy.” Journal of The Minerals, Metals & Materials Society, September: 32–36.

del Bosque, Antonio, Fernández-Arias, Pablo, and Vergara, Diego. 2025. “Advances in the Additive Manufacturing of Superalloys.” Journal of Manufacturing and Materials Processing 9 (215): 1–31.

Eliasen, K. M., T. L. Christiansen, and M. A. J. Somers. 2010. “Low-Temperature Gaseous Nitriding of Ni-Based Superalloys.” Surface Engineering 26 (4): 248–255.

Guan, Hao, Wenxiang Jiang, Junxia Lu, Yuefie Zhang, and Ze Zhang. 2023. “Precipitation of δ Phase in Inconel 718 Superalloy: The Role of Grain Boundary and Plastic Deformation.” Materials Today Communications 36 (August).

Herring, Daniel H. 2011. “Stress Corrosion Cracking.” Industrial Heating, October: 22–24.

Herring, Daniel H. 2012. Vacuum Heat Treating: Principles, Practices, Applications. BNP Media II, LLC.

Herring, Daniel H. 2019. “The Heat Treatment of Inconel 718.” Industrial Heating, June: 12–14.

Lee, Gang Ho, Ang Ho, Minha Park, Byoungkoo Kim, Jong Bae Jeon, Sanghoon Noh, and Byung Jun Kim. 2023. “Evaluation of Precipitation Phase and Mechanical Properties According to Aging Heat Treatment Temperature of Inconel 718.” Journal of Materials Research and Technology 27 (Nov–Dec): 4157–4168. https://doi.org/10.1016/j.jmrt.2023.10.196

Lee, Shin-Chin, Shih-Hsien Chang, Tzu-Piao Tang, Hsin-Hung Ho, and Jhewn-Kuang Chen. 2006. “Improvements in the Microstructure and Tensile Properties of Inconel 718 Superalloy by HIP Treatment.” Materials Transactions 47 (11): 2877–2881.

Loria, Edward A. 1988. “The Status and Prospects of Alloy 718.” Journal of Materials, July: 36–41.

Polasani, Ajay, and Vikram V. Dabhade. 2024. “Heat Treatments of Inconel 718 Nickel-Based Superalloy: A Review.” Metals and Materials International: 1204–1231.

Sharghi-Moshtaghin, Reza, Harold Kahn, Yindong Ge, Xiaoting Gu, Farrel J. Martin, Paul M. Natishan, Arrell J. Martin, Roy J. Rayne, Gary M. Michal, Frank Ernst, and Arthur H. Heuer. 2010. “Low-Temperature Carburization of the Ni-Base Superalloy IN718: Improvements in Surface Hardness and Crevice Corrosion Resistance.” Metallurgical and Materials Transactions A 41A (August): 2022–2032. https://doi.org/10.1007/s11661-010-0299-y

Shipley, Jim. 2023. “Hot Isostatic Pressing and AM: How to Improve Product Quality and Productivity for Critical Applications.” Metal AM 9 (3).

U.S. Patent No. 3,046,108.

Acknowledgments: This paper would not have been possible without discussions, guidance and contributions from a number of individuals in both the heat treat industry and academia.

Special Note: Inconel® is a registered trademark of Special Metals Corporation group of companies.

About the Authors:

Dan Herring
“The Heat Treat Doctor®”
The HERRING GROUP

Dan Herring, who is most well known as The Heat Treat Doctor®, has been in the industry for over 50 years. He spent the first 25 years in heat treating prior to launching his consulting business, The HERRING GROUP, in 1995. His vast experience in the field includes materials science, engineering, metallurgy, equipment design, process and application specialist, and new product research. He is the author of six books and over 700 technical articles.

Nikolai Alexander Hurley
Intern
The Heat Treat Doctor®

Nikolai Alexander Hurley is a young academic, interning with The Heat Treat Doctor®.

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

IN 718 Part 1: History, Applications, and Production Read More »

Ask The Heat Treat Doctor®: Why Use Partial Pressure in Vacuum Furnaces?

/ HARDENING TECHNICAL CONTENT, MEDICAL HEAT TREAT TECHNICAL, VACUUM FURNACES TECHNICAL CONTENT

Ask The Heat Treat Doctor® has returned to bring 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. In this installment, Dan Herring explains how partial pressure atmospheres prevent evaporation and achieve bright, oxide-free parts in vacuum furnaces.

This informative piece was first released in Heat Treat Today’s December 2025 Annual Medical & Energy Heat Treat print edition.

Have questions or feedback? We’d love to hear from you — reach out to our editorial team at editor@heattreattoday.com.

Operating in vacuum can often lead to problems related to evaporation, that is, literally “boiling away” elements present in the materials being heat treated. This affects surface integrity, functionality, performance, and in some rare cases altering the chemical composition of the base (or filler) metal.

One way to overcome this problem is to introduce a gas partial pressure higher than that of the material’s vapor pressure. Different gas choices, introduction methods, and controls are available to the heat treater. The natural question is, how and when should they be used? Let’s learn more.

What is Partial Pressure?

In simplest terms, the partial pressure of a gas introduced into a vacuum furnace is the force exerted by that gas (or gases) constrained in the vacuum vessel. If only a single gas is present, the partial pressure of the system is the same as the total pressure. For a multi-gas system, air is a good example to look at. At sea level with atmospheric pressure 760 torr (760 mm Hg) and at an altitude of 3,657 m (12,000 ft), the atmospheric pressure is only 483 Torr (Table A).

Table A. Partial Pressure of Individual Gases Present in Air | Source: Jones 1997

In vacuum systems, when the chamber atmosphere is evacuated to a high enough vacuum level — commonly between 10⁻³ Torr (0.1 micron) and 10⁻⁵ Torr (0.01 microns) — issues of evaporation are likely to occur during heat up and holding at temperature. As such, nitrogen or a truly inert gas is introduced below a predetermined temperature at a controlled rate to a fixed partial pressure range and then controlled within this range. One then isolates the high vacuum portion of the pumping system and employs bypass circuitry using the mechanical pump to introduce a continuous flow of gas equal to the pumping capacity (throughput) at the required operating pressure (Figure 1 below).

Figure 1. Typical partial pressure piping on a vacuum furnace
Key:
A: Incoming gas supply line
B: Backfill line
C: Quench solenoid
D: Partial pressure line
E: Partial pressure solenoid valve
F: Partial pressure (micrometer) needle value
G: Inlet into furnace
Source: Courtesy of Vac-Aero International

Why Do We Need to Use Partial Pressure in a Vacuum Furnace?

There is no hard and fast rule for partial pressure settings used for processing various materials in the heat treat industry. However, from a practical standpoint, there are two process considerations for determining partial pressure. The first is the metal-oxide reduction partial pressure. The partial pressure of oxygen at a given temperature determines the direction of the reaction and consequently whether the part is “bright” or “discolored” (oxidized). These values are typically in the range of 10⁻⁶ Torr to 10⁻² Torr. This is why materials like titanium alloys and superalloys must be processed at extremely low vacuum levels. The second consideration is the vaporization of metal at high temperature and hard vacuum. The metal solid-to-vapor partial pressures require higher pressures to avoid alloy depletion. These higher pressures often produce sufficient dilutions of contaminants to drive the reaction to be reducing.

What is often overlooked or misunderstood is that higher levels of partial pressure “dilute” any oxygen or water vapor partial pressure but still can produce oxide free “bright” parts at higher pressures. This dilution also occurs, for example when a retort is purged with nitrogen or argon to achieve clean parts. The oxygen partial pressure is reduced by dilution rather than by vacuum. In addition, it cannot be overemphasized that oxidation present on parts from exposure to the atmosphere and moisture absorbed by the furnace lining when the door is open are critical in running clean work. Oxidation occurs on heat up, but when the temperature is high enough and conditions are right, we can reverse the oxidation reaction so the parts will clean up. This is why it is harder to bright temper than to bright harden.

In batch vacuum furnaces, combination hardening and tempering cycles are used to take advantage of the furnace configuration in which parts stay in the furnace for the full process. Often, the same parts will discolor if tempered in the same furnace after they have been removed and the furnace exposed to air.

Also, a thorough understanding of the required component properties and material characteristics (e.g. alloy composition, grain size, hardenability response) is needed to design the final vacuum heat treat cycles and select the final partial pressure settings.

Figure 2. Chromium deposits / discoloration in the area of a graphite cooling nozzle | Source: The HERRING Group, Inc

For example, stainless steels, tool steels, and more exotic alloys run in a vacuum furnace will benefit substantially from the use of partial pressure atmospheres. In most heat treat shops, partial pressure cycles begin around 760°C (1400°F) at pressure from 1–1.5 Torr (1000–1500 microns). This is primarily because chromium present in many of these materials and in our baskets/fixtures evaporates noticeably at temperatures and pressures within normal heat treatment ranges. At around 990°C (1800°F), chromium will vaporize rapidly as a function of both vacuum level and time. In general, the practical operating vacuum level for most materials is significantly above their equilibrium vapor pressures. It is also helpful at times to know the temperature at which individual elements exceed a critical (10⁻⁶ g/cm²-s) vaporization rate (Herring 2015).

In practice, heat treaters often observe greenish discoloration (chromium oxide) on the interior of their vacuum furnaces (Figure 2), the result of chromium vapor reacting with air leaking into the hot zone. Otherwise, the evaporation deposit is bright and mirror-like. To avoid these types of deposits contaminating both the furnace and the parts run in it, an operating partial pressure between 1 Torr and 5 Torr (1,000 microns to 5,000 microns) is typical for parts that will boil away their elemental constituents.

Chromium Coloration

Heat treaters should be aware that although the most common color of chromium discoloration is green, the color is dependent on chromium’s oxidation state (Table B). For example, Cr (II) compounds typically appear blue, Cr (III) compounds appear green, and Cr (VI) compounds appear orange or red.

Notes: * Most commonly observed colors
Table B. Oxidation Colors of Chromium and Chromium Compounds

Table B provides a more detailed breakdown of chromium’s oxidation states and associated colors.

Which Partial Pressure Gas(es) Can We Use?

Argon, nitrogen, and hydrogen are the most common partial pressure gases. Often, argon is preferred as it is a truly inert gas and tends to “sweep” the hot zone; that is, being a heavier molecule, it tends to reduce evaporation compared with nitrogen or hydrogen. Specialized applications, such as those in the electronics industry, may use helium or even neon (if an ionizing gas is needed). Gases having a minimum purity of 99.99% and a dew point of -60°C (-76°F) or lower should be specified.

Certain cautions are in order. For example, nitrogen may react with certain stainless steels and titanium bearing alloys resulting in surface nitriding. In the case of hydrogen, the normally near neutral vacuum atmosphere can be sharply shifted to a reducing atmosphere to prevent oxidation of sensitive process work or for furnace/fixture bakeout/cleanup cycles. Embrittlement by hydrogen is a concern for certain materials (e.g., Ti, Ta).

Figure 3. 410 stainless steel housings, hydrogen partial pressure (1,000 microns) at 1010°C (1850°F) | Source: Courtesy of Vac-Aero International, Inc
Figure 4. Knee implants (cobalt-chromium-molybdenum alloy) vacuum heat treated under an argon partial pressure at 1 Torr (1,000 microns) to prevent elemental evaporation | Source: Courtesy of Vac-Aero International, Inc

In Summary

Partial pressure atmospheres are required in many heat treating and brazing operations to achieve desired results. Introduction of the partial pressure gas into the furnace hot zone at one or more locations and controlling the partial pressure injection gas stream as a continuous flow, rather than trying to operate at a specific pressure, are critical considerations. The choice of partial pressure gas is also important both from a cost and quality standpoint.

References

Herring, Daniel H. 2014. Vacuum Heat Treatment. Vol. 1. Troy, MI: BNP Media.

Herring, Daniel H. 2015. Vacuum Heat Treatment. Vol. 2. Troy, MI: BNP Media.

Houghton, R., Jr. n.d. Private correspondence, Spectrum Thermal Processing.

Jones, W. R. 1997. “Partial Pressure Vacuum Processing – Part I and II.” Industrial Heating, September/October.

Jones, William. n.d. Private correspondence, Solar Atmospheres Inc.

Fabian, R., ed. 1993. Vacuum Technology: Practical Heat Treating and Brazing. Materials Park, OH: ASM International.

The Boeing Company. n.d. “Practical Vacuum Systems Design Course.”

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.

Ask The Heat Treat Doctor®: Why Use Partial Pressure in Vacuum Furnaces? Read More »

Un Giro Bienvenido: Autolimpieza en Hornos revolucionado por Sistema de Bombas Inteligentes

/ AEROSPACE HEAT TREAT TECHNICAL CONTENT, VACUUM FURNACES TECHNICAL CONTENT, VACUUM PUMPS GAUGES VALVES TECHNICAL CONTENT

¿Y si su horno de vacío pudiera limpiarse automáticamente? En esta entrega de Technical Tuesday, Bob Hill, FASM, presidente de Solar Atmospheres of Western PA and Michigan, explora una revolucionaria configuración de bomba de vacío doble que elimina la necesidad de disolventes, envoltura con lámina metálica y prelimpieza manual.

Este artículo informativo se publicó por primera vez en Heat Treat Today’s December 2025 Annual Medical & Energy Heat Treat print edition. Traducido por Víctor Zacarías.

To read this article in English, click here.

Introducción

Los hornos de vacío requieren un entorno excepcionalmente limpio para procesar componentes críticos, desde dispositivos médicos hasta componentes aeroespaciales. Sin embargo, la limpieza de componentes, laboriosa y que consume mucho tiempo para garantizar la pulcritud del horno y las piezas, no tiene por qué ser necesariamente realizada por personas. Con las bombas adecuadas, su horno de vacío puede limpiarse automáticamente. Descubra cómo sería un ciclo de limpieza al vacío totalmente integrado mediante una innovadora configuración de doble bomba de vacío primario.

En el ámbito del tratamiento térmico al vacío, donde los componentes críticos suelen tener una forma casi final con una mínima o nula eliminación de material, la estética superficial del producto final es fundamental para el usuario final. En sectores como el aeroespacial, el de dispositivos médicos y el de generación de energía, el procesamiento al vacío se ha vuelto cada vez más valioso, no solo por su precisión, sino también por su capacidad para eliminar operaciones posteriores, lo que en última instancia ahorra tiempo y dinero.

Dadas estas ventajas, los clientes suelen estar dispuestos a pagar un precio premium por un trabajo limpio y brillante. Para lograr estos resultados perfectos, las empresas de tratamiento térmico al vacío exigen que las piezas recibidas estén limpias y libres de aceite. Sin embargo, lo que se considera “limpio” en un entorno de fabricación rara vez cumple con los exigentes estándares requeridos para el procesamiento térmico al vacío. Por ello, muchos tratadores térmicos adoptan medidas de limpieza secundarias para garantizar la limpieza de las piezas y proteger sus hornos de vacío de la contaminación por aceites de maquinado, lubricantes, tintas, oxidación o compuestos de pulido.

Figura 1. Horno de desengrasado al vacio. Fuente: Solar Atmospheres

Limpieza previa al tratamiento térmico: desafíos tradicionales

Antes de cualquier tratamiento térmico al vacío, los componentes deben limpiarse a fondo para eliminar contaminantes orgánicos e inorgánicos. Las prácticas habituales incluyen inmersión en disolvente, secado y desengrasado por vapor. Esta limpieza tiene como objetivo eliminar los residuos que pueden volatilizarse y depositarse dentro del horno de vacío, lo que podría comprometer la calidad de la pieza y dañar la zona caliente y la pared fría del horno.

Sin embargo, los productos de limpieza de uso común suelen ser inflamables, tóxicos, estar sujetos a regulaciones ambientales y su eliminación resulta costosa una vez empleados.

Figura 2. (Izquierda) Desengrasante de vapor y limpieza con solvente y (derecha) estación de envoltura con papel aluminio. Fuente: Solar Atmospheres
Figura 3. Como medida de protección para evitar daños en el horno por posibles contaminantes procedentes de fuentes anteriores, las piezas listas para el tratamiento térmico se envuelven en papel de aluminio. Fuente: Solar Atmospheres

Dado que las plantas de tratamiento térmico comerciales procesan piezas procedentes de miles de operaciones previas, cada una con su propio conjunto de contaminantes, la contaminación cruzada representa un riesgo significativo. El embalaje con lámina de acero inoxidable se utiliza a menudo como medida de protección, aislando las piezas del ambiente del horno. Si bien el empaque suele ser eficaz, puede ser laborioso, costoso e incluso potencialmente peligroso. Aun con el equipo de protección personal adecuado, los bordes de la lámina son extremadamente filosos. El embalaje con lámina sigue siendo una de las principales preocupaciones en materia de salud y seguridad para los empleados.

El horno para MIM: el catalizador para la innovación

Hace cinco años, Solar Atmospheres, con sede en el oeste de Pensilvania, recibió el encargo de sinterizar piezas pre-sinterizadas mediante moldeo por inyección de metal (MIM) a 1200 °C. Los aglutinantes presentes en estas piezas de armas de fuego se volatilizaron durante el proceso y contaminaron gravemente el horno de vacío, lo que ocasionó largos periodos de inactividad y mantenimiento.

Figura 4. Piezas de acero inoxidable 17-4PH brillantes y limpias tras el tratamiento térmico en un horno de desengrasado al vacío. Fuente: Solar Atmospheres

En lugar de construir una trampa fría tradicional para capturar los volátiles, el director ejecutivo, William Jones, desarrolló una solución más innovadora: una trampa caliente diseñada para desviar y capturar los contaminantes antes de que se depositaran dentro del horno. Esta adaptación proactiva ha demostrado mejorar drásticamente la calidad de las piezas, eliminando la laboriosa y frecuente limpieza de las zonas calientes y las paredes frías.

Tras finalizar ese trabajo de MIM, el horno subutilizado impulsó la experimentación. Este horno adaptado demostró un buen rendimiento con aglutinantes no deseados. Así pues, nos propusimos probar cómo adaptar este mismo sistema para eliminar impurezas de piezas de producción diaria. Tras exhaustivas pruebas con componentes no críticos de acero inoxidable grado PH, se perfeccionó un ciclo de limpieza y envejecimiento totalmente integrado, basado en vacío. Este desarrollo ha sustituido desde entonces a los costosos métodos tradicionales de prelavado y al peligroso envoltorio en aluminio, produciendo componentes aeroespaciales 17-4 PH consistentemente limpios y brillantes.

Horno de vacío autolimpiante: Cómo funciona

La innovación clave reside en una configuración de doble bomba de vacío primario.

(Izquierda) Figura 5. Sistema de bombeo de dos etapas.
(Derecha) Figura 6. Salida calefactada del sistema de bombeo n.° 1.
Fuente: Solar Atmospheres

Sistema de bombeo n.° 1: Bombeo inicial y eliminación de contaminantes:

  • Los componentes se cargan en el horno sin envolver ni limpiar.
  • Durante el bombeo inicial, solo se activa la bomba de vacío primario n.° 1.
  • Un aumento gradual de la temperatura permite que los contaminantes se vaporicen y salgan de la zona caliente a través de un puerto calefactado hacia la bomba n.° 1.
  • Los contaminantes quedan atrapados de forma segura en el aceite de la bomba, la «trampa caliente».

Sistema de bombeo n.° 2: Transición al tratamiento térmico:

  • Una vez completado el bombeo, se aísla la bomba n.° 1.
  • El sistema de bombeo n.° 2, que incluye una bomba de vacío primario, una bomba de refuerzo, una bomba de difusión y una bomba de mantenimiento, entra en funcionamiento.
  • A continuación, la cámara se lleva a 1 x 10⁻⁵ Torr y se inicia el ciclo térmico de vacío estándar.

Esta secuencia de bombeo en dos etapas limpia tanto las piezas como la cámara antes del tratamiento térmico sin necesidad de abrir la puerta del horno.

Resultados y beneficios

Este horno de vacío y proceso recientemente desarrollados producen lo siguiente:

  • Piezas más limpias: La limpieza por vacío penetra en barrenos ciegos, roscas y chaveteros con mayor eficacia que los métodos tradicionales de desengrase con solventes o vapor.
  • Reducción de lesiones: El proceso elimina la necesidad de envolver con lámina metálica, lo que mejora significativamente la seguridad de los empleados.
  • Ventajas ambientales y económicas: El proceso reduce o elimina el uso de solventes químicos, disminuye la mano de obra asociada con la limpieza previa y el embalaje, y reduce los costos de disposición de residuos peligrosos.
  • Mejoras en el mantenimiento del horno: Las zonas calientes y las paredes frías se mantienen impecables, sin necesidad de desmontajes semanales. El aceite de la bomba n.° 1 se cambia cada dos semanas, lo que elimina los problemas de bloqueo de la bomba de vacío debido a la contaminación del aceite.

Conclusión: Un avance revolucionario en el procesamiento al vacío

Históricamente, la limpieza de las piezas en el tratamiento térmico al vacío ha sido un desafío constante, a menudo abordado con mano de obra costosa, productos químicos y el peligroso uso de lámina de acero inoxidable o titanio para su envoltura. El innovador sistema de limpieza al vacío de doble bomba de Solar Atmospheres, integrado a la perfección con un ciclo estándar de tratamiento térmico al vacío, redefine las mejores prácticas de la industria.

Este concepto de “horno autolimpiante” no solo ofrece acabados superiores en las piezas, sino que también mejora la seguridad, reduce el impacto ambiental y disminuye los costos operativos. En un mundo donde la precisión, la limpieza y la sostenibilidad son más importantes que nunca, este avance podría crear una revolución en el procesamiento al vacío limpio.

Acerca del autor:

RObert (Bob) Hill PresidentSolar Atmospheres Michigan Source: Solar Atmospheres
Robert (Bob) Hill, FASM
Presidente
Solar Atmospheres de Western Pensilvania y Michigan
Fuente: Solar Atmospheres

Bob Hill, FASM, presidente de Solar Atmospheres de Western Pensilvania y Michigan, comenzó su carrera en Solar Atmospheres en 1995 en la planta principal ubicada en Souderton, Pensilvania. En 2000, el Sr. Hill fue designado para la puesta en marcha de la segunda planta de Solar Atmospheres, Solar Atmospheres of Western PA, en Hermitage, Pensilvania, donde se especializó en el desarrollo de tecnología de hornos de gran tamaño y procesamiento de titanio. Además, en 2009 recibió el prestigioso Titanium Achievement Award de la International Titanium Association. En 2022, Bob asumió la presidencia de su segunda planta, Solar Atmospheres de Michigan.

Para más información: Contacte con Solar Atmospheres o visite www.solaratm.com.

Un Giro Bienvenido: Autolimpieza en Hornos revolucionado por Sistema de Bombas Inteligentes Read More »

A Welcome Diversion: Smart Pump System Revolution for Self-Cleaning Furnaces

/ AEROSPACE HEAT TREAT TECHNICAL CONTENT, VACUUM FURNACES TECHNICAL CONTENT, VACUUM PUMPS GAUGES VALVES TECHNICAL CONTENT

What if your vacuum furnace could clean itself? In this Technical Tuesday installment, Bob Hill, FASM, president of Solar Atmospheres of Western PA and Michigan, explores a revolutionary dual roughing pump configuration that eliminates the need for solvents, foil wrapping, and manual pre-cleaning.

This informative piece was first released in Heat Treat Today’s December 2025 Annual Medical & Energy Heat Treat print edition.

Para leer el artículo en español, haga clic aquí.

Introduction

Vacuum furnaces require an exceptionally clean environment to process critical components, from medical devices to aerospace. But laborious, time-consuming component cleaning to ensure purity of the furnace and parts does not necessarily need to be done by people. With the right pumps, your vacuum furnace can clean itself. Explore what a fully integrated, vacuum-based cleaning cycle could look like by leveraging an innovative dual roughing pump configuration.

In the vacuum heat treating world, where critical components are often near-net-shape with minimal to zero stock removal, the surface aesthetics of the final product are critical to the end user. Across industries like aerospace, medical devices, and power generation, vacuum processing has become increasingly valued — not only for its precision, but also for its ability to eliminate downstream operations, ultimately saving cost and time.

Given these benefits, clients are frequently willing to pay a premium for bright, clean work. To achieve these pristine results, vacuum heat treaters insist that incoming parts must be clean and oil-free. However, what qualifies as “clean” in a manufacturing environment rarely meets the exacting standards required for vacuum thermal processing. As a result, many commercial heat treaters adopt secondary cleaning measures to ensure part cleanliness and to protect their vacuum furnaces from contamination by machining oils, lubricants, Dykem, oxidation, or polishing compounds.

Figure 1. Vacuum degreasing furnace. Source: Solar Atmospheres

Pre-Heat Treatment Cleaning: Traditional Challenges

Before any vacuum heat treatment, components must be thoroughly cleaned to remove organic and inorganic contaminants. Common practices include solvent immersion, drying, and vapor degreasing. This cleaning step is designed to eliminate residues that can volatilize and redeposit within the vacuum furnace, potentially compromising part quality and damaging the vacuum furnace hot zone and cold wall.

However, commonly used cleaning agents are often flammable, toxic, environmentally regulated, and costly to dispose of when spent.

Figure 2. (Left) Vapor degreaser and solvent cleaning and (right) foil wrapping station. Source: Solar Atmospheres
Figure 3. As a defensive measure to prevent furnace damage from potential upstream sourced contaminants, parts ready for heating are wrapped in stainless steel foil. Source: Solar Atmospheres

Given that commercial heat treaters process parts from thousands of upstream operations, each introducing its own set of contaminants, cross-contamination becomes a significant risk. Stainless steel foil wrapping is often used as a defensive measure, isolating parts from the furnace environment. While wrapping is often effective, it can be labor-intensive, expensive, and even potentially hazardous. Even with the proper PPE, the foil edges are razor-sharp. Foil wrapping continues to be a top health and safety concern for employees.

The MIM Furnace: A Catalyst for Innovation

Five years ago, Solar Atmospheres of Western Pennsylvania was tasked with sintering pre-sintered metal injection molding (MIM) parts at 2200°F. The binders present in these firearm parts volatilized during processing and heavily contaminated the vacuum furnace, resulting in extensive downtime and maintenance.

Figure 4. Bright, clean 17-4PH stainless steel parts post heat treatment in a vacuum degreasing furnace. Source: Solar Atmospheres

Instead of constructing a traditional “cold trap” to capture volatiles, CEO William Jones developed a more innovative solution: a “hot trap” designed to divert and capture contaminants before they could deposit inside the furnace. This proactive adaptation has proven to drastically improve part quality while eliminating the laborious and frequent cleaning of hot zones and cold walls.

After that MIM job ended, the underutilized furnace prompted experimentation. This adapted furnace proved to perform well on unwanted binders. So, we set out to test how this same system could be adapted to remove impurities from everyday production parts. After extensive trials using noncritical PH-grade stainless steel components, a fully integrated, vacuum-based cleaning and aging cycle was perfected. This development has since replaced traditional expensive pre-cleaning methods and dangerous foil wrapping, producing consistently clean and bright 17-4 PH aerospace components.

The Self-Cleaning Vacuum Furnace: How It Works

The key innovation lies in a dual roughing pump configuration.

(Left) Figure 5. Two-stage pumping system. (Right) Figure 6. Heated exit port on Pumping System #1.
Source: Solar Atmospheres

Pumping System #1 — Initial Pump-Down and Contaminant Removal:

  • Components are loaded into the furnace unwrapped and uncleaned.
  • Only Roughing Pump #1 is activated during the initial pump-down.
  • A slow temperature ramp allows contaminants to vaporize and exit the hot zone through a heated port into Pump #1.
  • Contaminants are safely trapped in the pump’s oil — the “hot trap.”

Pumping System #2 — Transition to Heat Treatment:

  • After off gassing is complete, Pump #1 is isolated.
  • Pump #2 system, which includes a roughing pump, booster, diffusion, and holding pump, takes over.
  • The chamber is then brought to 1 x 10⁻⁵ Torr and the standard vacuum thermal cycle proceeds.

This two-stage pumping sequence cleans both the parts and the chamber prior to heat treatment without ever opening the furnace door.

Results and Benefits

This newly developed vacuum furnace and process produces the following:

  • Cleaner parts: Vacuum cleaning penetrates blind holes, threads, and keyways more effectively than traditional solvent or vapor degreasing methods.
  • Injury reduction: The process eliminates the need for hazardous foil wrapping, significantly improving employee safety.
  • Environmental and cost advantages: The process reduces or eliminates chemical solvent use, cuts labor associated with pre-cleaning and wrapping, and reduces hazardous waste and disposal costs.
  • Furnace maintenance improvements: Hot zones and cold walls remain pristine — no weekly teardowns. Pump #1 oil is changed biweekly, eliminating roughing pump seizure concerns due to contaminated oil.

Conclusion: A Breakthrough in Vacuum Processing

Historically, part cleanliness in vacuum heat treating has been a persistent challenge — one often addressed through costly labor, chemicals, and dangerous stainless steel or titanium foil wrapping. Solar Atmospheres’ innovative dual-pump vacuum cleaning system, integrated seamlessly with a standard vacuum heat treatment cycle, redefines industry best practices.

This “self-cleaning furnace” concept not only delivers superior part finishes but also enhances safety, reduces environmental impact, and cuts operating costs. In a world where precision, cleanliness, and sustainability matter more than ever, this advancement may very well create a revolution in clean vacuum processing.

About The Author:

RObert (Bob) Hill PresidentSolar Atmospheres Michigan Source: Solar Atmospheres
Robert (Bob) Hill, FASM
President
Solar Atmospheres of Western PA and Michigan
Source: Solar Atmospheres

Bob Hill, FASM, president of Solar Atmospheres of Western PA and Michigan, began his career with Solar Atmospheres in 1995 at the headquarters plant located in Souderton, Pennsylvania. In 2000, Mr. Hill was assigned the responsibility of starting Solar Atmospheres’ second plant, Solar Atmospheres of Western PA, in Hermitage, Pennsylvania, where he has specialized in the development of large furnace technology and titanium processing capabilities. Additionally, he was awarded the prestigious Titanium Achievement Award in 2009 by the International Titanium Association. In 2022, Bob became president of his second plant, Solar Atmospheres of Michigan.

For more information: Contact Solar Atmospheres or visit www.solaratm.com.

A Welcome Diversion: Smart Pump System Revolution for Self-Cleaning Furnaces Read More »

Pit LPC: A Modern Take on High Throughput Heat Treat

/ CARBURIZING TECHNICAL CONTENT, MANUFACTURING HEAT TREAT TECH, VACUUM FURNACES TECHNICAL CONTENT

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)
Figure 1b: The view from the operator platform

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 4a. Heating Rate
Figure 4b. Cooling Rate

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
Figure 5b. Essential process data and schematic flow of the carburizing process in the Pit-LPC vacuum 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%).
Figure 8b. Exemplary post-processing microstructure pictures of sample 4 surface. Magnifications x100 (left) and x500 (right). Nital etching 2%. Martensite with residual austenite (approx. 20%).

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

/ 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.

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.

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