There are many avenues for achieving new feats in sustainability. One foundational method of pursuing sustainability is efficient furnace design. In this Control’s Corner installment of Technical Tuesday, Stanley Rutkowski III, senior applications engineer, RoMan Manufacturing, Inc., explores ways to design furnace electrical power systems for efficiency.
This informative piece was first released inHeat Treat Today’sJune 2025 Buyers Guide print edition.
In the world of industrial heat treating, sustainability isn’t just a buzzword; it’s a measurable outcome of engineering decisions. While discussions around energy usage often focus on renewable sources or carbon offsets, the path to sustainability begins much earlier — with the design of the furnace’s electrical power system.
From transformers and load configurations to modern control technologies, every part of the furnace power pathway affects how efficiently energy is used — and how much of it is wasted. A well-designed system doesn’t just heat effectively; it does so with less resistance, fewer losses, and minimal disruption to the power grid.
The Power Triangle: Real, Reactive, and Apparent
Understanding sustainability starts with understanding how energy is consumed. Utility companies bill based on more than just energy (kWh). They measure and potentially build via:
Real power (kW): the usable energy
Reactive power (kVAR): the energy lost due to inductance and system inefficiencies
Apparent power (kVA): the total power delivered, including losses
Power factor: the ratio of real power to apparent power, indicating system efficiency
Peak demand: the highest level of power drawn during a billing period
Furnace systems with poor power factor or high reactive power incur more cost, even if their real energy usage is low. That’s why electrical design is so critical.
Control Systems: The Shift to Digital
Legacy systems, such as tubes or saturable reactor-based VRTs, have largely given way to more efficient SCR- (silicon controlled rectifier) and IGBT- (insulated-gate bipolar transistor) based controls. IGBT technology, in particular, offers high-frequency switching, reduced losses, and excellent power factor performance. These systems also provide communication protocols — giving real-time insight into power draw, voltage stability, control temperatures, and even predictive maintenance alerts.
Digital communication allows users to evaluate trends over time. For example, changes in DC bus voltage or output current may signal a degrading heating element, enabling early intervention. Smart controls also help avoid peak demand charges by shifting high-load operations to off-peak hours or adjusting recipes to consume less total power.
Load Configurations and Layout
Load configuration is equally as important: single-phase, Scott-T two-phase, or balanced three-phase arrangements. Poorly balanced systems place stress on utility infrastructure and reduce power factor. Balanced loads, especially when combined with IGBT control, lower disturbances to the grid and increase efficiency.
Physical layout also plays a key role. Long conductor runs increase resistance and inductive reactance, which raises energy consumption and heat loss. “Close coupling” the transformer and conductors near the furnace feedthrough reduces losses and improves power delivery, which is important for sustainability and cost savings.
AC vs. Rectified DC Power
Finally, consider how power is delivered. While AC remains common and easy to install, rectified DC systems eliminate voltage zero-crossings, resulting in more stable heating and reduced thermal stress on elements. For high-precision applications like carburizing or annealing, DC systems can extend equipment life and improve thermal uniformity.
Conclusion
Energy sustainability in heat treating isn’t just about switching to greener sources — it starts with how power is delivered, controlled, and consumed. Getting a power conversion expert involved early in the planning and system design process ensures that every component is optimized for efficiency, reliability, and long-term performance. This early collaboration helps manufacturers reduce energy costs, extend equipment life, and achieve more sustainable operations without compromising results.
About The Author:
Stanley F. Rutkowski III Senior Applications Engineer RoMan Manufacturing, Inc.
Stanley F. Rutkowski III is the senior applications engineer at RoMan Manufacturing, Inc., working on electrical energy savings in resistance heating applications. Stanley has experience in welding, glass and furnace industries from R&D, design, and application standpoints. For more than 15 years, his focus has been on energy savings applications in industrial heating applications.
In this Technical Tuesday installment, Kazunori Hokaku, business director/general manager/sales engineering dept. at Tokai Konetsu Kogyo shares the sustainability benefits of SiC heating elements.
This informative piece was first released inHeat Treat Today’sMay 2025 Sustainable Heat Treat Technologies print edition.
In recent years, Silicon Carbide (SiC) heating elements have been increasingly used in demanding applications involving high temperatures and extreme atmospheres. Battery material manufacturing is one of many such applications. Therefore, improved service life contributes to increased productivity and sustainability as well as reduced industrial waste. This article discusses the long service life for recrystallized SiC heating elements having both excellent oxidation and corrosion resistance.
Tokai Konetsu Kogyo in Japan has been manufacturing EREMA® SiC heating elements since 1936. SiC heating elements are categorized as ceramic heating elements, which are widely used in a temperature range between 932°F–2912°F (500°C–1600°C) as shown in Figure 1.
Figure 1. Temperature range for heatingTable 1. Example of applications for SiC
heating elements
The heat value per unit area (i.e., watt density) of SiC heating elements is quite high, 5 to 10 times that of metallic Nichrome wire heating elements, for example. SiC heating elements are chemically stable and an environmentally friendly source, free of air and noise pollution compared to gas-fired or liquid fuel systems. As such, they are chosen and used for a variety of applications, such as Lithium-ion battery material (i.e., cathode/anode/solid state battery materials), powder metallurgy, aluminum, hardening and case hardening applications (e.g., carburizing), electronic parts (MLCC, ferrite), and dental materials as shown in Table 1.
SiC heating elements come in a variety of shapes, namely straight rod, U-shaped, and W-shaped designs. They are affordable and easy to handle compared to other ceramic heating elements. It is important to remember, however, that their service life is drastically influenced by high temperatures and the atmosphere.
The failure mechanism of a SiC heating element to its service life is shown in Figure 2. SiC reacts with O2 and creates SiO2, by which the resistance of the heating element increases.
Therefore, increasing bulk density and reducing specific surface area are key to service life longevity. This relationship between bulk density and service life in alkaline atmosphere (Li2CO3) has been explored by Tokai Konetsu Kogyo using scanning electron microscopy (SEM) photos with results as shown in Figure 3.
Figure 2. Mechanism of resistance increase (service life)
Silicon Carbide 101
■ Electric heating elements are a popular choice of many heat treaters. They come in a variety of shapes, sizes, and materials. One of the most common types are silicon carbide (SiC) heating elements, known by several tradenames including Globar™ and StarBar™. They are used extensively throughout the heat treating industry when high temperatures, maximum power, and heavy duty cycles are required.
A SiC heating element is typically, but not always, an extruded tubular rod or cylinder made from high purity grains of silicon carbide that are fused together by either a reaction bonding process or a recrystallization process at temperatures in excess of 3900°F (2150°C). The result is a chemically stable material with a low thermal expansion coefficient and little tendency to deform.
Spiral-cut silicon carbide heating element design provides increased resistance for applications up to 3000°F (1650°C)
Recrystallization forms fine grains of silicon carbide that act as “bridges” or connection points between larger grains thus forming conductive pathways. The number of bridges formed dictates the material’s resistance: the greater the number, the lower the resistance. The secret to the creation of a good heating element is controlling this formation process within the material to develop a consistent electrical resistance
The factors that influence the life of a SiC heating element include the type of furnace atmosphere, watt density, operating temperature, type of service (continuous or intermittent), and maintenance. Furnace type, design, and loading play an important role as well. SiC heating elements are extremely versatile operating, for example, in air up to 3000°F (1650°C).
Finally, the choice of heating element depends on many factors. For example, SiC heating elements are capable of higher operating temperatures and higher watt loadings than say metallic elements; they are self-supporting and can be used in furnaces either too wide or too long to be spanned by other element types and are relatively easy to change while hot. SiC heating elements are used extensively in brazing and sintering furnaces running continuously at or above 2050°F (1120°C) and for other processes where the temperature range lies between 2375°F (1300°C) and 2725°F (1500°C).
With permission from the author, Dan Herring, the information cited has been used in part from, Herring, Daniel H. “Electric Heating Elements Part One: Silicon Carbide.” Industrial Heating, September 2008. ■
SEM photos show the Sustainable Development Goals (SDGs) model observed increased bulk density with low porosity and very thick neck growth of SiC grains. The specific surface area for the SDGs model of 0.03 m2/g by Brunauer–Emmett–Teller (BET) method is smaller than that of the standard high-density grade of 0.05 m2/g.
Figure 3. Life test (resistance increase in alkaline atmosphere)
As a result, the graph in Figure 3 shows that the service life for the EREMA®SDGs model (BD = 2.65) is the longest, which means a reduction not only in downtime of furnace operation but also of industrial waste.
About The Author:
Kazunori Hokaku Business Director/General Manager/Sales Engineering Dept Tokai Konetsu Kogyo
Kazunori Hokaku graduated from Kyoto Institute of Technology in 1985 with a major in ceramics. He has been with Tokai Konetsu Kogyo Co., Ltd., since 1985 and is currently the business director/general manager/sales engineering dept.
By Steven Christopher, senior engineer at Super Systems Inc., and Katie Bastine, former quality manager at ThermoFusion.
The three letters, P-I-D, send shivers down most spines; tuning may induce an actual headache. This has proven true for decades, but why is the concept so overwhelming? This article will attempt to answer that difficult question with simple considerations.
This informative piece was first released inHeat Treat Today’sMay 2025 Sustainable Heat Treat Technologies print edition.
PIDs (Proportional-Integral-Derivative) need not be anxiety-producing. Let’s break it down to reduce the stress, but first, let’s credit one of the world’s deepest thinkers. Einstein defined insanity as, “Repeating the same thing over and over and expecting different results.”
Is this happening in our industry? Why does every Proportional-Integral-Derivative (PID) article begin with tuning a new controller? In reality, very few new controllers are installed. Instead, a failing TUS dictates re-tuning an existing controller. Let’s start with an existing controller, and then intentionally RUIN our PIDs.
Katie Bastine, quality manager of Nadcap-certified Thermo-Fusion of Hayward, CA, agreed to help and offered one of the company’s many Endothermic nitriding or batch furnaces. We settled on a vacuum furnace with graphite heating elements, which is a perfect candidate because it was relatively quick to respond and easy to manipulate.
What Are PIDs?
According to Blink author Malcolm Gladwell, we need a basic understanding of PIDs, and perhaps no more. His fantastic book details the brain’s ability to thin-slice situations — meaning the ability to make quick, often correct, decisions. He discusses in great depth the importance of data for experts, but he hypothesizes that too much data for the average person negatively influences the decision-making process. Gladwell claims, “The role of those other factors is so small … that extra information is more than useless. It’s harmful. It confuses the issues.”
This may be our mistake: too much information freezing our ability to act rather than empowering us. The goal of this article is not to train experts but rather to help with that often-paralyzing first step.
Consider the following definitions:
Proportional band (Pb) compares the error at a single moment or the difference between the set-point and control TC. Adjusting the Pb parameter determines how large an error is required to reduce/increase output.
Integral (or reset) compiles this same error over a period of time, appropriately adjusting to the Pb’s output.
Derivative (or rate) monitors the rate of change, estimating future error and “applying the brakes” when necessary. The remainder of this article limits theory and focuses on observations.
TIP: Understand the units. Pb can be expressed as percentage, degrees, or gain. Integral and derivative can be expressed as seconds, minutes, or repeats/minute. This article will use percentage and seconds.
Note: An increase to Pb (percentage) will have the same outcome as an opposite decrease to Pb (gain).
Evaluation Criteria
Before evaluating PIDs, it is important to agree what makes a good one. Th at list could be quite long, so this article will intentionally avoid considerations such as repeatability and recovery time. Instead, we will evaluate:
Aggressiveness — rate at which temperature approaches setpoint
Overshoot — both initial overshoot followed by how quickly it returns
Steady-state — oscillations (both period and amplitude) once settled out Aggressiveness is when the output first reduces as temperature approaches the final setpoint. Reducing too early sacrifices heat-up time while simultaneously improving overshoot. Like many PIDs, a delicate balance exists between any two parameters — a constant set of “give and take.” This consideration is less important when ramping to the final setpoint, because the output typically never reaches its maximum.
Are PIDs the Problem?
Algorithms are stable by nature; input data then calculate output. Thus, changes in behavior are rarely “failing PIDs,” but rather some external factor. If ever there was a time to pause, this is it. Before embarking on the time-consuming effort of tuning, evaluate the furnace holistically. What changed? Are PID changes masking a physical issue? Make sure you are fixing the right problem.
Many confuse PIDs with uniformity. While these concepts coexist, uniformity tends to indicate the health of a furnace, which is influenced by such things as heating system design, element/tube/valve condition, insulation, radiant effects, changes to rheostat/trim settings, and convection turbulence. A negative change in one may result in a failed TUS and prove impossible for PIDs alone to overcome.
Remember, a sudden, exaggerated loss in control suggests PIDs are not at fault.
TIP: Forget the TUS. If the control TC is good, then so are the PIDs.
Uniformity is defined by two characteristics: Delta and balance. Delta is the difference between the coldest and hottest temperature. Balance is the relationship between these temperatures and the control TC. Consider Figures 1 and 2 representing an AMS2750F Class 2 furnace with +/-10°F tolerances.
Figure 1 centers around setpoint. With a delta of 21°F, however, no amount of tuning will pass TUS.
Figure 2 reduces delta to 15°F, but the unbalanced nature results in a failing TUS on the lower limit. PIDs will never improve uniformity.
Poor uniformity (Delta) can be overcome by the aforementioned factors and (balance) by adjusting the control TC position or applying an offset (if allowed). The possible combinations are so wide they are beyond the scope of this article.
Pay Attention to Output
Output is an important (and often overlooked) tuning parameter. PID changes are driven by the control TC, but they have practical limits. These limits are often visible in the output well before they are in the control TC. Tuning efforts should always monitor the output for:
Backing off — temperature when output begins to reduce
Stability — ability of output to converge on an appropriate value
Response — noticeable difference in time for the control TC to respond to an output change
TIP: In addition to setpoint and control TC (PV), record output (CV) to better understand tuning. A lot happens in one minute, so try recording every 1–5 seconds if possible.
Healthy PIDs
Thermo-Fusion’s vacuum furnace ramped to 1000°F at 40°F/min with an aggressive approach, minimal overshoot and continued a “straight line” at soak (using PIDs of 2.0/75/150). As the control TC neared soak, the output backed off 60°F before the soak temperature — neither too early nor too late. The output settled down after a few quick oscillations, suggesting the Pb was not too small.
Figure 3 demonstrates what PIDs should look like. Now let’s disrupt these values, learning from the result. We begin by exploring Pb’s effect because it has the most influence on the trio.
Figure 3. Perfect PIDs
TIP: When adjusting parameters, go big! Start with large (40–60%) changes, then fine-tune with smaller (10–20%) adjustments.
Increase Pb
Figure 4. Increasing Pb
Proportional band influences when output first reduces and how fast it adjusts. The first mostly impacts furnaces experiencing immediate setpoint changes. All furnaces, including those that ramp to final soak, must consider the second — how fast the output adjusts.
A “sweet spot” exists for Pb. Let’s consider the extremes. A Pb of “∞” backs off very early but too slowly. This results in either overshoot followed by slow, rolling oscillations or no overshoot but also failure to reach setpoint. Same cause, but very different outcomes.
Figure 4 demonstrates the first example: reducing early but too slowly to eliminate overshoot.
TIP: Decrease Pb until the output “bounces around”, then slightly increase Pb. This approach offers diminishing returns, with the output eventually becoming unstable.
Decrease Pb
Figure 5. Decreasing Pb
If increasing Pb slows the output, decreasing must offer the opposite effect. A Pb of “0.0” represents on/off control, backing off very late (at setpoint) but quickly (100% to 0% immediately) followed by rapid oscillations. A smaller Pb presents a double-edged sword, which is an advantage to furnaces with an immediate control/output response, but a disadvantage for those with a lagging relationship. This allows the output to wind up or down too much before the control TC responds.
A small Pb minimizes overshoot but sacrifices steady-state control. Pay special attention to the output (specifically the 1/4 Pb line on Figure 5). As the control TC approaches soak, there are tremendous output swings followed by instability — classic signs of too small a Pb.
TIP: Watch the output. If “bouncing around,” increase the Pb, which dampens output.
Increase Integral
Figure 6. Increasing Integral
Integral considers past error, “winding up” as large error exists and adding to the output. Small error conversely “unwinds” the Integral. A larger Integral parameter adds more to the Pb’s output. This may improve aggressiveness, but it sacrifices other aspects of a healthy PID.
Too large an Integral overemphasizes previous error, potentially resulting in overshoot, then quickly unwinding as the error becomes smaller, flattening the control TC. Integral has a second benefit: reducing “droop” as the control TC approaches soak only to prematurely stall. A third benefit compensates for a furnace that heats faster than it cools (or vice versa).
TIP: With similar overshoot to a large Pb, a large Integral differs with less undershoot before stabilizing.
If the control TC stalls before soak without closing, increase the Integral. If the control TC looks more like a saw tooth than a sine curve, increase the Integral.
Decrease Integral
Too small an Integral eliminates the PIDs knowledge of history, leaving all the work to the Pb. Error can change rapidly at any moment, which results in an equally rapid change in output. An appropriately sized Integral offers a smoothing effect on the system. Too small an Integral disregards previous error, possibly making the system unstable.
Figure 7. Decreasing Integral
Changes to Derivative
Derivative is difficult to simplify, but (channeling our inner Malcolm Gladwell) let’s try. Derivative is perhaps most easily thought of as a counterweight to the actions of P-I alone. Derivative evaluates the error’s current rate of change to estimate future error. This forecasting allows Derivative to prematurely reduce or increase output.
Derivative is frequently overused and often not required. Exceptions must be evaluated on a case-by-case basis. A visible indicator suggesting a benefit from Derivative is a delayed response between the control TC and output. As output increases, does the control TC immediately rise? Or does it take a while to respond?
TIP: P-I alone often can’t overcome a significant lag between the control TC and output. Increasing Derivative will counteract the delay.
Summary
We hope this article provides the confidence to take that difficult first step. The beauty of PIDs is they are free to make and easy to undo. Therefore, do not be intimidated in taking that first step. Worst-case scenario, you revert. Pair these tips with the following guidelines, and you will be fine.
Change only one parameter at a time.
Cool the furnace between tests; don’t increase +100°F only to try again.
If you overshoot, don’t abandon ship — observe steady-state. You often learn more from failure than success.
Document, document, document! Simplify your thinking, and don’t simplify your notes.
If stumped, place the controller in manual output, forget the setpoint but watch for stability. If the furnace can’t control, then how can the PIDs?
About The Authors:
Steven Christopher Senior Engineer Super Systems Inc.
Steven Christopher has been involved in countless projects for both captive and commercial heat treaters implementing critical technology applications. He brings a vast knowledge base as it relates to industrial automation, and his experience with heat treat equipment is second to none.
What’s the relationship between excess air and your bottom-line? In this article, Jim Roberts, President, U.S. Ignition, shares how to increase efficiency and reduce waste in your heat-treating operations.
This informative piece was first released inHeat Treat Today’sApril 2025 Annual Induction Heating & Melting print edition.
A furnace guy walks into a heat treat shop . . . and notices there is a little bit of a yelp to the burners, or the furnace operator mentions the furnace is slowing down on heat up recovery times from a cold load. Or, if you are responsible for fuel costs and monitoring the gas meters, you might notice that situation is slipping in the wrong direction. Or, the burners seem to be dumping soot on your floor. We discussed that in past columns — remember?
Well, it’s all got to do with air. It may seem odd to talk about air when the objective is to utilize fuel at an optimum efficiency, but that’s how we intend to get combustion under control. Let’s go after the air. You remember that we talked about making sure that combustion air sources (blowers, eductors, etc.) were all operating at optimum performance, so the air remains supplied as engineered when the equipment was new. So, now we have our air being delivered at the peak levels we want, but it looks like one of the air valves has shifted, which we covered in the last column on keeping the air sources clean.
This next little tidbit of information is intended to show us all how much this little-considered entity we call AIR can affect the bottom line. Here’s some info you might find interesting.
Eliminate Excess Air
If controls have moved or another phenomenon has caused the burners to lean out, it could cost you a fortune. Most burners are designed to burn with a small percentage of excess air (less than 15%).
Exceptions would include air heating equipment and low temperature drying operations where the excess air is used to control the temperature of the flame. If you operate a burner that has been designed to run at 10–15% excess air and the burner controls or settings drift into the range of 50% excess air (that is a difference of 2–3% O2 or 7.5% O2 in the products of combustion), the difference in an 1800°F oven operation is a calculated 9% loss of fuel efficiency. If you operate a 1 million BTU/hr burner, firing at 75% of the time six days a week for 50 weeks a year, your gas usage would be approx. 5400 therms a year. If we calculate that your gas costs (delivered) are in the range of $4 per 1,000 cu/ft, keeping one burner in tune would save approximately $1,950 per year.
What!!! If you are running a good-sized batch furnace with four burners, that’s a cool $7,800 dollars per year. A ten burner continuous line is going to save almost $20,000 dollars per year. All that just because you cared enough to check excess air levels regularly.
Of course, wasting fuel because you are heating air instead of product is a terrible thing. But don’t forget you can go the other way, too, and go fuel rich with the settings. Then, you take the chance of actually damaging equipment with the carbon you could be producing in a reducing (excess fuel) situation. Carbon can affect all sorts of equipment life, including shortening burner component life and reducing radiant tube and fixture life. It’s not good. Don’t do it. No excess air and no excess fuel will lead you to a happier and more profitable life.
As always, I recommend that you associate your business with the furnace and combustion technicians in your area who can help you make sure everything stays in tune. We’ll chat in the next edition of Heat Treat Today about how to keep a handle on this in-house, so you can tell your experts what you are seeing and start saving yourself gobs of fuel!
For more information: Contact Jim Roberts at jim@usignition.com
In this Technical Tuesday installment, Thomas Wingens, Founder & President, WINGENS CONSULTANTS; Dr. Dermot Monaghan, Managing Director, and Dr. Erik Cox, Manager of New Business Development, Gencoa, train readers for finding both real and evasive virtual vacuum leaks.
Leak detection is difficult enough with a “real” leak, but “virtual” leaks present their own challenges. To enhance cost savings and further process efficiencies, it’s essential to have leak sensor technology that can effectively monitor the vacuum chamber and pinpoint these problematic leaks.
This informative piece was first released inHeat Treat Today’sMarch 2025 Annual Aerospace Heat Treating print edition.
Uncontrolled impurities in a vacuum furnace can significantly affect the quality of vacuum heat treating and brazing processes. They can compromise the integrity of the processed material, leading to defects, reduced performance, and increased costs.
Real vs. Virtual Leaks
Real leaks are physical openings in the vacuum system that allow external gases to enter the chamber. These can be cracks, weld failures, improperly installed fittings, faulty seals from damaged or worn O-rings on doors, rotating assemblies, or other components of the vacuum furnace.
The impact on quality includes:
Oxidation and contamination: Real leaks introduce atmospheric gases (like oxygen, nitrogen, and moisture) into the vacuum chamber, which can lead to oxidation of the materials being treated or brazed, as well as other forms of contamination.
Inconsistent results: The presence of unwanted gases can interfere with the chemical processes required for proper heat treatment or brazing, leading to inconsistent metallurgical results.
Reduced mechanical properties: Contamination and oxidation can weaken the materials being processed, leading to defects and reduced mechanical properties of the final product.
Difficulties in achieving desired vacuum: Real leaks can prevent the system from reaching or maintaining the necessary vacuum levels, leading to longer cycle times or failed processes.
Figure 1. Pumping times based on residual water vapor
Real leaks are often easier to detect, especially larger leaks, which can be identified by hissing sounds or the inability of the furnace to pump down. They can be located using methods such as pressure rise tests, solvent detection, or helium leak detectors.
Virtual leaks, however, are much harder to detect as they are not physical openings but rather trapped volumes of gas within the vacuum system that slowly release over time. These trapped volumes are typically found in blind holes, porous materials, or unvented components. Even more problematic are leaks from internally sealed systems, such as water cooling or hydraulics. Leaks from these areas cannot be detected via a leak detector, as the water or oil media can “mask” the leak site and prevent the tracer gas from penetrating.
Aside from increasing the pump time it takes to reach the required vacuum levels, leaks can be a continuous source of contamination within the vacuum chamber. Outgassing can be especially problematic during the heating cycle as it can lead to large vacuum “spikes” or a rise in pressure, affecting the stability of the process environment. Gases released from virtual leaks can contaminate the materials being treated. For example, residual solvents or water vapor from cleaning or incomplete drying can lead to contamination and outgassing. It can be small volumes of air or gas trapped at the bottom of threaded holes or trapped volumes between two O-rings that are not properly vented. Also, outgassing from various hydrocarbons in porous materials such as low-density graphite or powder metallurgy components can release unwanted gases when heated up.
They usually become apparent during the pump-down cycle when the ultimate pressures are not reached or when it takes a long time to reach blank-off pressure. Traditional leak detectors will not pick up virtual leaks.
Detecting Virtual Leaks Accurately
However, residual gas analysis (RGA) and remote plasma emission monitoring (RPEM) can identify virtual leaks by monitoring the composition of gases in the chamber. RPEM offers advantages over traditional quadrupole mass spectrometry (QMS) RGA, particularly in large vacuum systems. Unlike RGAs, RPEM technology operates over a much wider pressure range (50 mbar to 10-7mbar) without requiring additional pumps. The RPEM detector is located outside the vacuum chamber, making it more robust against contamination and high pressures, which commonly damage RGA detectors. This external setup also reduces maintenance needs, as RPEM avoids frequent rebuilds required for traditional RGAs in volatile environments.
Figure 2. Functionality and pressure range of the OPTIX sensor
An example of this newer sensor is the OPTIX, which enables real-time monitoring and process control by providing immediate feedback to maintain chemical balance and ensure product quality. By identifying specific gas species, the sensor allows versatile leak detection with faster problem-solving and continuous system monitoring. Determining the nature of the gas leak will be a clear indication of where the problem originates. Also, whether the gas levels are stable or decreasing will point towards either a real leak or outgassing problem. Unlike RGAs, this sensor does not require highly skilled staff for operation, further lowering the technical burden. Its effectiveness in harsh environments with volatile species makes it a robust and versatile tool for industrial vacuum processes.
Conclusion
By understanding the differences between real and virtual leaks, and their specific impacts on vacuum heat treating and brazing, operators can implement more effective detection and prevention strategies, ultimately leading to improved product quality and process efficiency.
Attention to design, manufacturing, and assembly processes is critical to minimize the occurrence of leaks. This includes proper venting of components, use of appropriate sealing methods, and high-quality welding. Ensuring that components and materials are properly cleaned and dried before being introduced into the vacuum system can reduce outgassing.
Regular leak checks, including leak-up-rate tests, are essential for identifying both real and virtual leaks. Advanced gas analysis techniques are very useful for identifying the type of leak and its source through analysis of the gases in the vacuum chamber. Th e method provides continuous on-line monitoring, rather than periodic leak testing when there is a “suspicion” of a problem.
In the demanding environment of vacuum heat treating and brazing, the OPTIX sensor’s advanced technology not only simplifies leak detection and process control, but also delivers significant cost savings through reduced maintenance and operational expenses. Adopting this type of technology gives operators the ability to enhance vacuum system performance, improve product quality, and achieve greater process efficiency.
About The Authors:
Thomas Wingens Founder & President Wingens Consultants Industrial Advisor Center for Heat Treating Excellence (CHTE)
Thomas Wingens is the Founder and President of Wingens Consultants, and has been an independent consultant to the heat treat industry for nearly 15 years and has been involved in the heat treat industry for over 35 years. Throughout his career, he has held various positions, including business developer, management, and executive roles for companies in Europe and the United States, including Bodycote, Ipsen, SECO/WARWICK, Tenova, and IHI-Group.
Dr. Dermot Monaghan founded Gencoa Ltd. in 1994. Following completion of a BSc in Engineering Metallurgy, Dermot completed a PhD focused on magnetron sputtering in 1992 and went on to be awarded with the C.R. Burch Prize from the British Vacuum Council for “outstanding research in the field of Vacuum Science and Technology by a young scientist.” He has published over 30 scientific papers, delivered an excess of 100 presentations at international scientific conferences, and holds a number of international patents regarding plasma control in magnetron sputter processes.
Eric Cox Manager, New Business Development Gencoa
Dr. Erik Cox is a former research scientist with experience working in the U.S., Singapore, and Europe. Erik has a master’s degree in physics and a PhD from the University of Liverpool. As the manager of New Business Development at Gencoa, Erik plays a key role in identifying industry sectors outside of Gencoa’s traditional markets that can benefit from the company’s comprehensive portfolio of products and know-how.
Por Josh Tucker, Gerente de Calentamiento por Inducción, Tucker Induction Systems, Inc. Traducido por Víctor Zacarías, Global _ Thermal Solutions México
This informative piece was first released inHeat Treat Today’sApril 2025 Induction Heating & Melting print edition.
Las investigaciones sobre bobinas de inducción con impresión 3D han demostrado que estas bobinas son más resistentes y tienen una vida útil más larga en comparación con las bobinas fabricadas tradicionalmente. Lea sobre cómo la fabricación aditiva elimina pasos como el brazing de las uniones y ofrece nuevas posibilidades de diseño.
Tucker Induction Systems comenzó a explorar la posibilidad de utilizar la tecnología de impresión 3D para fabricar bobinas y descubrió que, en muchos casos, las bobinas impresas en 3D eran más resistentes y duraderas que sus contrapartes fabricadas Tradicionalmente.
Cuando llegó el COVID-19, el condado de Macomb, Michigan, puso en marcha una iniciativa llamada Proyecto DIAMOnD (Distributed, Independent, Agile Manufacturing on Demand). Proporcionó a los fabricantes PyMEs impresoras 3D de tipo modelado por deposición fundida marca Markforged como una forma de fabricar rápidamente el equipo de protección personal tan necesario para la pandemia y para ayudar a los fabricantes de tamaño pequeño a mediano a superar los problemas de la cadena de suministro que plagaron la industria durante la crisis.
Estábamos ansiosos por adquirir experiencia práctica en fabricación aditiva a través de la iniciativa DIAMOnD y, al hacerlo, descubrimos que despertó nuestra curiosidad sobre la posibilidad de imprimir en 3D nuestras bobinas y nuevas formas de diseñarlas que van más allá de las capacidades del mecanizado tradicional.
En 2021, iniciamos un proceso de investigación y desarrollo de dos años de duración para la impresión de bobinas y descubrimos que, al imprimir en 3D bobinas de inducción, podíamos aumentar drásticamente la resistencia de las bobinas y, potencialmente, alargar su vida útil. La experiencia ha abierto nuevos caminos en el diseño de nuestras bobinas, además de brindarnos la capacidad de diseñar bobinas utilizando métodos que van más allá de las capacidades del mecanizado tradicional.
Figura 1. Bobinas de temple por inducción impresos en 3D.
Es de conocimiento común en la industria que las partes más débiles de una bobina son las uniones soldadas, pero a través del proceso de I+D, hemos aprendido que al imprimir las bobinas en 3D, es posible eliminar la mayoría, o incluso todas las uniones soldadas en la bobina. Esto aumenta la resistencia y, potencialmente, la vida útil de una bobina. Después de años de pruebas y evolución, los resultados finales fueron mejores de lo que esperábamos, lo que demuestra que las bobinas se pueden imprimir y durarán en el campo.
Sin embargo, hubo algunos desafíos a la hora de adaptarse al uso de la tecnología de impresión 3D. Por ejemplo, el tipo de impresión en cobre que necesitábamos no se estaba realizando en los Estados Unidos, lo que fue un obstáculo para intentar formar un proceso que diera como resultado una bobina impresa con éxito. Luego, uno de los mayores desafíos después de que cerramos el proceso y el material, fue el diseño de los conductos de refrigeración internos para las bobinas. Los conductos debían diseñarse de manera que fueran autosufi cientes y sin restricciones. Teníamos que producir el mismo caudal que las bobinas fabricadas tradicionalmente y asegurarnos de que estábamos dirigiendo la refrigeración hacia las áreas correctas. Descubrir eso requirió muchos intentos fallidos (oportunidades de aprendizaje) antes de lograr el éxito.
Una vez logrado ese objetivo, instalamos una impresora 3D de metal en Tucker Induction en enero de 2024 y hemos estado imprimiendo con éxito todo tipo de bobinas. Algunos ejemplos incluyen bobinas de diámetro interno, estáticas y de escaneo.
Los beneficios de utilizar bobinas impresas en 3D
Si bien las bobinas tradicionales (como nuestra bobina intercambiable de cambio rápido para sistemas de inducción de dos vueltas y diseños de bobina estática con sujeción precisa a presión) han cambiado la industria, la capacidad adicional de la impresión 3D nos permite imprimir piezas dimensionalmente exactas y duraderas que son capaces de funcionar en el campo y que pueden ir más allá de las barreras del mecanizado tradicional.
Figura 2. Bobina de inducción estática impresa en 3D con retenes
El ahorro de tiempo es una de las mayores ventajas. Debido a que la impresora 3D puede seguir funcionando “fuera de turno”, el tiempo de procesamiento desde la impresora hasta el cliente es mucho más corto en comparación con las bobinas fabricadas tradicionalmente. Nos referimos al tiempo de procesamiento como el tiempo adicional necesario para completar el ensamblaje de la bobina después de la impresión. En algunas situaciones, es posible imprimir un ensamble de bobina completo con la bobina lista inmediatamente para ser enviada al cliente. En otras ocasiones, puede ser necesario soldar con brazing adicional o realizar detalles complementarios para completar el ensamblaje.
Dado que todas las bobinas son diferentes, el tiempo de procesamiento varía de una bobina a otra. Sin embargo, al imprimir la mayor parte posible del conjunto, podemos limitar la cantidad de trabajo adicional necesario para completar el ensamble.
La resistencia y la longevidad potencial de las bobinas impresas en 3D son ventajas adicionales. Las partes más débiles de la bobina son las uniones soldadas, pero el proceso que utilizamos para imprimir las bobinas reduce drásticamente la cantidad de uniones soldadas, lo que hace que la bobina sea una construcción sólida. Esto da como resultado un producto que será más resistente en el entorno de inducción y tiene el potencial de durar más que su contraparte fabricada tradicionalmente.
En lo que respecta a la vida útil de las bobinas impresas en 3D, nuestra base es que las bobinas impresas deben durar al menos tanto como las bobinas fabricadas tradicionalmente. Sin embargo, en nuestra investigación hemos visto que, en promedio, nuestras bobinas impresas en 3D pueden durar entre dos y tres veces más que las bobinas fabricadas tradicionalmente. Si bien la longevidad de cada bobina depende de cada caso, ya que hay muchos factores que influyen en la vida útil de una bobina, una de nuestras bobinas de prueba originales todavía está funcionando en el campo con más de un millón de ciclos de calentamiento.
Mientras seguimos mejorando los procesos y los diseños, también nos esforzamos por reducir el tiempo de reparación. Reparar y devolver las bobinas de nuestros clientes en un esfuerzo por limitar su tiempo de inactividad siempre ha sido algo por lo que nos esforzamos con nuestras bobinas tradicionales, pero hemos descubierto que las bobinas impresas en 3D son más fáciles de reparar. Dado que las múltiples uniones soldadas no son un problema en las bobinas impresas, se reducen las posibilidades de causar problemas adicionales mientras se trabaja en la reparación original. Si la reparación consiste en reemplazar el cabezal de la bobina, podemos recuperar la impresión original y ejecutarla nuevamente, en lugar de tener que volver a maquinar ensamblar y soldar toda la bobina, lo que reduce significativamente el tiempo de reparación de muchas bobinas impresas en 3D.
Limitaciones de las bobinas de impresión 3D
A pesar de las ventajas de la impresión 3D de bobinas de inducción y del hecho de que la capacidad de imprimir bobinas te lleva a pensar que cada bobina debe imprimirse, hay algunos casos en los que todavía es más efectivo utilizar la fabricación tradicional.
Figura 3. Estructuras de muestra impresas en 3D.
Por ejemplo, las bobinas que son más grandes de lo que la máquina puede imprimir (el tamaño de nuestra plataforma de impresión es de aproximadamente 12 x 12 x 13 pulgadas) pueden ser un factor limitante. En otras ocasiones, la bobina se puede fabricar más rápido utilizando métodos tradicionales. La impresora tiene limitaciones y no es la mejor opción para ciertas bobinas. Por ejemplo, las bobinas que son menos intrincadas y están hechas de tubos son un tipo que sería un mejor candidato para la fabricación tradicional; estas bobinas simplemente requieren envolver un tubo de cobre alrededor de un mandril.
El futuro de las bobinas impresas en 3D
Seguimos investigando y perfeccionando los procesos de impresión 3D de nuestras bobinas y nos esforzamos por ofrecer a nuestros clientes el mejor producto posible. Para ello, debemos permanecer atentos y estar dispuestos a aprender y mejorar continuamente nuestros diseños y procesos.
A medida que aprendemos más y perfeccionamos nuestros procesos de impresión 3D de bobinas, creo que las bobinas impresas en 3D desempeñarán un papel fundamental en el futuro de la industria. Hemos demostrado que la impresión 3D de bobinas no solo es posible, sino que en algunos casos las bobinas impresas en 3D pueden superar a sus contrapartes fabricadas tradicionalmente.
Sobre El Autor:
Josh Tucker Gerente de Calentamiento por Inducción Tucker
Induction Systems, Inc.
Josh Tucker se graduó de licenciatura dela Grand Valley State University y luego fue contratado como jefe de compras enTucker Induction Systems. Desde que comenzó hace ocho años, el rol y las capacidades de Josh se han expandido al maquinado, la electroerosión, la impresión 3D y el grabado láser. También organiza las operaciones diarias y el fl ujo del taller. Josh fue reconocido en la clase 2024 de 40 Under 40 de Heat Treat Today.
Para más información: Contacta a Josh Tucker en JTucker@tuckerinductionsystems.com.
In this Technical Tuesday installment,Josh Tucker, Manager of Induction Heating, Tucker Induction Systems, Inc., relates new research conducted on the strength of coils which have been produced through 3D printing.
This informative piece was first released inHeat Treat Today’sApril 2025 Induction Heating & Melting print edition.
Research on 3D printing induction coils finds that coils are stronger and have a longer life when compared to traditionally manufactured coils. Read about how additive manufacturing removes steps like brazing the joints and provides new design capabilities.
Tucker Induction Systems began exploring the possibility of using 3D printing technology to manufacture coils and found that, in many cases, 3D printed coils were stronger and longer lasting than traditionally manufactured counterparts.
The quest to develop 3D printed coils began in 2020. When COVID-19 hit, Macomb County, Michigan, started an initiative called Project DIAMOnD, which stands for Distributed, Independent, Agile Manufacturing on Demand. It provided small-to-medium-sized area manufacturers with Markforged Fused Deposition Modeling-style 3D printers as both a way to quickly manufacture much needed personal protective equipment for the pandemic and to help small-to-mid-sized manufacturers overcome the supply chain issues that plagued industry during the crisis.
We were eager to gain hands-on additive manufacturing experience through the DIAMOnD initiative and, in doing so, found that it sparked our curiosity about the possibility of 3D printing our coils and new ways to design them that go beyond the capabilities of traditional machining.
In 2021, we began a two-year research and development process of printing coils and discovered that by 3D printing induction coils we were able to drastically increase the strength of the coils and potentially lengthen the useful life of the coil. The experience has opened new realms in designing our coils, as well as giving us the ability to design coils using methods that go beyond the capabilities of traditional machining.
It is common industry knowledge that the weakest parts of a coil are the braze joints, but through the R&D process, we have learned that by 3D printing the coils, it is possible to eliminate most, if not all, braze joints in the head of a coil. This increases the strength and, potentially, the life of a coil. After years of testing and evolving, the end results were better than we expected, proving that the coils can be printed and will last in the field.
Figure 1. 3D printed single-shot hardening induction coil heads
However, there were some challenges in adapting to using 3D printing technology. For example, the type of copper printing we required was not being done in the United States, which was an obstacle in trying to form a process that resulted in a successfully printed coil. But one of the biggest challenges after we locked down the process and material was in designing the internal cooling passages for the coils. The passages needed to be designed in a way that was self-supporting and non-restricting. We had to produce the same flow rate as traditionally made coils and ensure we were driving the cooling into the right areas. Figuring that out took many failed attempts — learning opportunities — before achieving success.
Once that goal was achieved, we installed a metal 3D printer at Tucker Induction in January 2024 and have been successfully printing all different types of coils. Some examples include two turn ID, spindle, single-shot, and scanning coils.
The Benefits of Using 3D Printed Coils
While traditional coils (such as our interchangeable, quick-change coil for two-turn induction systems and single-shot designs with accurate clamping pressure) have changed the industry, the additional capability of 3D printing allows us to print dimensionally accurate, durable parts that are capable of performing in the field and that can go beyond the barriers of traditional machining.
Figure 2. 3D printed single-shot induction coil with keepers
3D printed coils bring several worthwhile benefits to the table including time savings, longevity, and faster coil repair. Time savings is one of the biggest advantages. Because the 3D printer can run “lights out,” the processing time from the printer to the client is far shorter when compared to traditionally fabricated coils. We refer to the processing time as the additional time needed to complete the coil assembly after printing. In some situations, it is possible to print a completed coil assembly with the coil immediately ready to be sent to the client. Other times, additional brazing or supplemental details may be required to complete the assembly.
Since all coils are different, the processing time varies from coil to coil. However, by printing as much of the assembly as we can, we are able to limit the amount of additional work needed to complete the job.
Strength and potential longevity of 3D printed coils are additional advantages. The weakest parts of the coil are the braze joints, but the process we use to print the coils drastically reduces the amount of braze joints, thus making the workforce of the coil a solid construction. This results in a product that will be stronger in the induction environment and has the potential to outlast its traditionally manufactured counterpart.
When it comes to the lifetime of the 3D printed coils, our baseline is that the printed coils need to last at least as long as traditionally manufactured coils. However, in our research, we have seen, on average, that our 3D printed coils can last two to three times longer than traditionally manufactured coils. While the longevity of each coil is case dependent, as there are many factors that go into the lifespan of a coil, one of our original test coils is still running in the field with over one million heat cycles.
While continuing to improve processes and designs, we are also pushing to decrease the time for repairs. Getting our clients’ coils repaired and returned in an effort to limit their downtime has always been something we strive for with our traditional coils, but we have found that 3D printed coils are easier to repair. Since multiple braze joints are not an issue in printed coils, it reduces the chance of causing additional problems as you work on the original repair. If the repair consists of replacing the head of the coil, we are able to recall the original print and run it again, as opposed to having to re-machine and re-assemble and braze the entire coil, significantly reducing the repair time of many 3D printed coils.
Limitations of 3D Printing Coils
Despite the advantages of 3D printing induction coils and the fact that the capability to print coils gets you into the mindset that every coil needs to be printed, there are some instances when it is still more effective to use traditional manufacturing.
Figure 3. 3D printed sample structures
For example, coils that are larger than the machine is capable of printing — our print bed size is roughly 12 x 12 x 13 inches — can be a limiting factor. Other times, the coil may be manufactured faster using traditional methods. The printer does have limitations, and it is not the best option for certain coils. For example, coils that are less intricate and made from tubing is one type that would be a better candidate for traditional manufacturing; these coils simply require wrapping copper tubing around a mandrel.
The Future of 3D Printed Coils
We are continuing to research and fine tune the processes of 3D printing our coils and strive to provide our clients with the best possible product. In order to do that, we must stay vigilant and be willing to continuously learn and improve our designs and processes.
As we learn more and perfect our 3D printing coil processes, I believe 3D printed coils will play a vital role in the future of the industry. We have proven that 3D printing coils is not just possible, but that in some cases 3D printed coils can outperform their traditionally manufactured counterparts.
About The Author:
Josh Tucker Manager of Induction Heating Tucker Induction Systems, Inc.
Josh Tucker graduated with a bachelor’s degree from Grand Valley State University and was then hired as the head of Purchasing at Tucker Induction Systems. Since starting eight years ago, Josh’s role and capabilities have expanded to machining, wire EDM, 3D printing, and laser engraving. He also organizes the day-today operations and flow of the shop floor. Josh was recognized in Heat Treat Today’s 40 Under 40 Class of 2024.
The Heat Treat Doctor® has returned to offer sage advice to Heat Treat Today readers and to answer your questions about heat treating, brazing, sintering, and other types of thermal treatments as well as questions on metallurgy, equipment, and process-related issues.
This informative piece was first released in Heat Treat Today’sApril 2025 Induction Heating & Melting print edition.
Of all the case hardening processes, boronizing (a.k.a. boriding) is perhaps the least understood and least appreciated. Let’s learn more.
In this era of using coating technologies (e.g., PVD, CVD, DLC) to produce hard, wear-resistant surface layers on component parts, one often forgets that there is a thermo-chemical treatment that often can outperform many of them.
Boronizing (a.k.a. Boriding)
Table 1. Examples of hardness levels achieved by boronizing*
*The hardness of the boride layer depends on the compound formed. For example, FeB is 1900–2100 HV, Fe2B is 1800–2000 HV, while Ti2B is 3000 HV.
Boronizing is a case hardening process that produces a very high surface hardness in steels and is used for severe wear applications (see Table 1). The layer of borides (FeB and Fe2B) formed also significantly increases corrosion resistance of the steel.
Boron is added to steels for its unique ability to increase hardenability and lower the coefficient of (sliding) friction. In addition, boron is used to control phase transformation and microstructure since the time-temperature-transformation curve for the material when boron is diffused into the surface is shifted to the right.
The Process
The boronizing process is typically run in a solid (pack), liquid, or gaseous medium. Each of these methods involves the diffusion of boron into the steel’s surface, but they differ in how boron is introduced and the conditions under which they operate.
In the pack boronizing, a powder mixture of boron compounds (typically boron carbide or sodium tetrafluoroborate) is packed around the steel workpieces. This pack is placed in a retort-style furnace where it is heated, typically with an argon cover gas, to temperatures ranging from 1300°F to 1832°F (700°C to 1000°C). The heat causes the boron to diffuse into the steel surface, forming a boride layer (Figure 1).
A key advantage of this method of boronizing is that it is highly effective for producing uniform boride coatings. It is particularly suitable for large parts or components that may not be suitable for immersion in a liquid or exposure to gaseous boron compounds.
In liquid boronizing, the steel is immersed in a molten bath containing boron-bearing compounds, typically a mixture of sodium tetraborate and other chemicals. The steel absorbs boron from the bath, forming a boride layer. The liquid process tends to be faster than the solid method and can be more economical for certain applications.
One of the challenges with liquid boronizing is that the process can be difficult to control in terms of coating thickness and uniformity. Therefore, this method is often used for smaller, simpler parts rather than large or complex geometries.
Gaseous boronizing involves exposing the steel to a boron-containing gas, typically diborane (B2H6) or boron trifluoride (BF3), at elevated temperatures. The boron diffuses from the gas onto the surface of the steel, forming the boride layer. Gaseous boronizing allows for better control over the process compared to the other two methods, but it requires specialized equipment to handle the toxic and reactive nature of the boron gases.
The advantage of gaseous boronizing lies in its ability to produce a uniform and controlled boride layer, especially for complex parts or those with intricate geometries.
When working with any boron-containing compounds, adequate ventilation and other safety precautions (e.g., masks, gloves) are required. If boron tetrafloride is present, extra precautions are necessary since it is a poisonous gas.
Typical processing temperature is in the range of 1300°F–1832°F (700°C–1000°C) with time at temperature from 1 to 12 hours. Typical case depths achieved range from 0.003″–0.015″ (0.076 mm to 0.38 mm) or deeper (Figure 2). Case depths between 0.024″ and 0.030″ require longer cycles up to 48 hours in duration.
Figure 1. Typical microstructure of a boronized component
The mechanical properties of the borided alloys depend strongly on the composition and structure of the boride layers. The most desirable microstructure a er boronizing is a single-phase boride layer consisting of Fe2B2. Plain carbon and low alloy steels are good candidates for boronizing, while more highly alloyed steels may produce a dualphase layer (i.e., boron-rich FeB compounds) because the alloying elements interfere with boron diffusion. The boron-rich diffusion zone can be up to seven times deeper than the boride layer thickness into the substrate.
The hardness of the borided layer depends on the composition of the base steel (Table 1). Comparative data on steels that have been borided versus carburized or carbonitrided, nitrided or nitrocarburized are available in the literature (see Campos-Silva and Rodriguez-Castro, “Boriding,” 651–702). The surface hardness achieved through boronizing is among the highest for case hardening processes. The boride layers typically exhibit hardness values in the range of 1000 to 1800 HV. This level of hardness helps prevent surface deformation under load, which is particularly beneficial in applications involving high contact pressures, such as gears, bearings, and automotive components.
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Boronizing can also lower the coefficient of friction on the surface of the steel. This is particularly useful in applications where reduced friction is necessary, such as in sliding or rotating parts that operate under high pressures. The reduced friction helps to minimize wear and energy consumption, improving the overall efficiency and longevity of the components.
Unlike other surface-hardening methods that can compromise the core properties of the material, boronizing tends to retain the toughness and ductility of the base steel. This means the steel remains strong and resistant to cracking or breaking while also benefiting from a hard, wear-resistant surface.
By contrast, when boron is used as an alloying element in plain carbon and low alloy steels, it is added to increase the core hardenability and not the case hardenability. In fact, boron can actually decrease the case hardenability in carburized steels. Boron “works” by suppressing the nucleation (but not the growth) of proeutectoid ferrite on austenitic grain boundaries. Boron’s effectiveness increases linearly up to around 0.002% then levels off.
Figure 2. Hardness-depth profiles on different borided steel* * Notes: 1. The boriding temperature was 1740°F (950°C) with six (6) hours of exposure 2. Hardness conversion: 1 GPa = 102 HV (Vickers hardness) 3. Depth conversion: 10 micrometers = 0.00039 inches
Boronizing Applications
Given the range of benefits that boronizing offers, it has found widespread use across many industries. Some of the most common applications include:
Automotive industry: Gears, camshafts, and valve components are often boronized to enhance wear resistance and extend their service life.
Aerospace: Parts exposed to high temperatures and wear, such as turbine blades, landing gears, and other critical engine components, benefit from the hard, wear-resistant coatings created by boronizing.
Cutting tools and dies: The high surface hardness and resistance to abrasion make boronized tools highly effective for machining and forming hard materials.
Mining and earthmoving equipment: Equipment like drill bits, shovels, and conveyor parts subjected to abrasive conditions can be boronized to improve their performance and reduce downtime.
Oil and gas: Valves, pumps, and other equipment exposed to corrosive fluids in the oil and gas industry benefit from the enhanced corrosion resistance of boronizing.
In Summary
Boronizing is not for everyone, but it is safe to say that it is the “forgotten” case hardening process, one that will find increasing use in the future as demand for better tribological properties increases. It is a highly effective surface treatment process that imparts significant benefits to steel, including enhanced wear and corrosion resistance, increased surface hardness, and improved frictional properties. By carefully selecting the boronizing method and optimizing process parameters, manufacturers can produce components with superior performance in demanding applications. As industries continue to push the boundaries of material performance, boronizing can be an essential technique for producing long-lasting, high-performance steel components.
References
Campos-Silva. I. E., and G. A. Rodriguez-Castro, “Boriding to Improve the mechanical properties and corrosion resistance of steels.” In Thermochemical Surface Engineering of Steels, edited E. J. Mittemeijer and M. A. J. Somers. Woodhead Publishing, 2014.
Herring, Daniel H. Atmosphere Heat Treatment, vol. I. BNP Media, 2014.
Kulka, Michal. “Current Trends in Boriding: Techniques.” Springer Nature, 2019.
Senatorski, Jan, Jan Tacikowski, and Paweł Mączyński. “Tribological Properties and Metallurgical Characteristics of Different Diffusion Layers Formed on Steel.” Inżynieria Powierzchni 24, no. 4 (2019).
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.
Part 1 of this article by Dave Deiwert, owner and president of Tracer Gas Technologies, was published inHeat Treat Today’sNovember 2024 Vacuum Heat Treatprint edition and online and explored finding leaks with and without a leak detector, the best equipment for leak detection, and 10 tips for finding a leak with a helium leak detector. In this week’s Technical Tuesday we bring you part 2, where Dave further addresses leak detection using a helium leak detector including modern advancements in helium leak detector technology, the best place to connect a leak detector, maintaining a leak detector, and discerning whether to repair or replace components with a leak.
This informative piece can be found in Heat Treat Today’sMarch 2025 Aerospace print edition.
Past Challenges in Leak Detector Operation
When I started my career in 1989, helium leak detectors required frequent maintenance, often caused by improper shutdown or power outage. Another problem with the older detectors is how easily someone can improperly disconnect the test line while it is still in test mode. These situations could cause backflow of diffusion pump oil. An improper shutdown or power loss often required a major overhaul of the leak detector before you could use it again.
If an operator or maintenance technician forgot the leak detector was still in test mode and disconnected the test line from the leak detector to the furnace, the inrush of air to the leak detector also would require a major overhaul of the leak detector. Sometimes the inrush of air would cause the filament in the mass spectrometer to burn out. Additionally, in the days of diffusion pump leak detectors, significant backflow of diffusion pump oil could enter the valve block and possibly the mass spectrometer.
Modern Advancements in Helium Leak Detectors
The first major improvement in leak detector design targeting reliability and significantly lowering the cost of ownership was replacing the diffusion pump in the detector with a turbo pump. Replacing the diffusion pump with a turbo pump in modern leak detectors allows that leak detector to get into test mode sooner at a higher crossover pressure.
Figure 1. Evaluating a vacuum furnace for leaks
In addition, the turbo pumped leak detectors are much less at risk for pressure bursts due to opening the test line while still in test mode or operating some process gas valve while the leak detector is in test mode. With diffusion pumped leak detectors, these events cause a significant maintenance event. But with a turbo pumped leak detector, most likely it will drop out of test mode but be ready to go back into it once the pressure burst event has been solved.
A third benefit of the turbo pumped leak detectors is they typically have a much better helium pumping speed during testing which helps with response time, reaching base leak rate sooner, and recovering more quickly after detecting a leak.
Lastly, leak detectors with greater helium pumping speed benefit with a greater signal-to-noise ratio.
The next major advancement in leak detector design was replacing tungsten filaments with thoria-coated iridium; today the whole leak detector industry is using yttria-coated iridium filaments. The newer fi lament materials operate at a lower temperature but the most significant benefit is how much more robust they are to pressure bursts. Tungsten filaments used in older leak detector mass spectrometer designs would “burn out,” creating an open circuit and loss of operational capability of the leak detector. My experience and that of others shows you can expect to get thousands of hours of more use from each modern filament vs. the old tungsten filaments. This development further aided the reliability and cost-effective ownership of leak detectors.
Another advancement is that modern detectors can now respond to sudden rises in test pressure. If an operator accidentally leaves the leak detector in test mode and then proceeds to disconnect the hose from the furnace, the leak detector will likely sense the sudden rise in test pressure, close the test valve, and then turn off the mass spectrometer filaments and amplifier to protect them and the turbo pump from the pressure spike. The leak detector will document the event as an alarm but soon be ready for the next test with no maintenance required.
Older technology leak detectors gave the user no status signals beyond:
Filament on or off
High vacuum for mass spectrometer gauge or status light
Sight glass for the rotary vane pump
Most likely an end user with an older leak detector has to rely on the manufacturer or other third-party service company to repair or provide preventative maintenance.
Newer technology leak detectors have a full range of alarms and status messages for any issues of concern. For example:
Filament on or off
Filament life or condition
Test port pressure
High vacuum gauge
Turbo pump controller status readings
Error messages for any problems detected
Next maintenance date required
Last calibration performed
Many other messages per the manufacturer’s manual
Figure 2. Dave with a vacuum pumping system recently remanufactured by Midwest Vacuum Pumps Inc. in Terre Haute, Indiana
Maintaining an Older vs. Modern Leak Detector
An end user or OEM still using diffusion pumped leak detectors with tungsten filaments is probably overhauling their leak detector every one to two years at best, or multiple times per year at worst. Depending on how much they use it and how knowledgeable their operators are, the obsolete leak detectors are probably costing them at least several thousands of dollars per event, not to mention the time lost in production as they wait to get a leak detector working so they can find the leak in their furnace.
On the other hand, an end user or OEM with a modern helium leak detector may be fortunate enough to have their model still in production by their supplier today. They can most likely go several to many years without maintenance beyond maintaining the oil quality and level in the rotary vane pump of the leak detector.
Where To Connect the Leak Detector
Figure 3. Leak testing a vacuum furnace
Th ere has been much discussion over the years on where to connect the leak detector to a vacuum furnace. Some think that because they are leak testing a furnace they should connect the leak detector directly to the furnace. While you can do that, you are asking a leak detector — typically with an NW25 vacuum connection or some type of hose barb connector — to compete with the typically very large port of the diffusion pump; in systems without a diffusion pump, the leak detector competes with the blower. In molecular flow level of vacuum, the conductance of helium to that 1” target is significantly lower than the conductance to the port of the valve to the diffusion pump or the blower (imagine a 1” vs. a 10” connection, for example).
It is best to connect to a port near the inlet of the blower, which is typically available. You would still be using an NW25 vacuum connection or smaller hose barb fitting, but you will be sampling the flow to the blower. The recommended connections from the leak detection to the blower should all be the same as to the leak detector test port. Using smaller connectors to the leak detector diminishes conductance to the leak detector from the furnace. This, in turn, decreases the performance of the leak detector.
It is also best to have a manually operated NW25 ball valve that is permanently installed at this point, which would be closed normally with a “blank” fitting clamped to the port on that valve. This would facilitate the following recommendation that preventative maintenance leak checks be completed during long furnace processes.
How To Conduct Preventative Maintenance Leak Checks During Operation
While the furnace is under vacuum in a long furnace process, place the leak detector in test mode. While in test mode, the leak detector creates a vacuum to the closed ball valve on the furnace, as previously recommended. Next, place the leak detector momentarily in standby mode. This closes the test valve of the leak detector but does not vent the test port. Then, open the ball valve. This lets the leak detector test port gauge show the current vacuum level now that it’s connected to the furnace. Now put the leak detector back into test mode.
At this point, you are ready to spray helium at potential leak points on the furnace. While many often begin checking with the leak detector hose at the ball valve to ensure they did not create a leak during assembly, then it is best to move to the opposite side of the furnace — to the furthest point of the vacuum system of the furnace — and slowly work back to the pumps.
A common question is how much helium should you spray? People often say they were taught to adjust the helium spray so that they get one or two bubbles in a glass of water per second or to adjust the spray so that they can barely feel it on their lips or tongue. That last one makes some people nervous. Then, it is basically like playing the hot and cold game as you spray the potentially leaking points of the furnace. More information on helium spray technique can be found in part 1 of this article.
Finding a Leak
The closer you get to a leak, the larger and faster the response will be on the leak rate meter of the leak detector. To confirm that you have located a leak, repeatedly spray the point of leakage and ensure that you get the same peak leak rate display and response time with each spray at that leak point.
Earlier we mentioned that you can accomplish preventative maintenance leak checks on furnaces while in a long process. This is because helium is inert, as mentioned in part 1 of this article. Many times, operators have told me they know of a persistent leak and have not been able to repair it; as the leak is so small, they say it does not affect their product quality. Therefore, it is possible for any furnace operator to: (a) do a preventative maintenance leak check and discover a leak they did not know they had, and then (b) have the option of marking or tagging that leak to do a preemptive repair at their convenience, as opposed to discovering it aft er it degrades to the point of causing a production shut down.
Figure 4. Dave in the front of a vacuum furnace at Mercer Technologies, Inc., in Terre Haute, Indiana
To Repair or Replace?
If you find a leak in a component like a valve, fitting, or thermocouple, you must then consider if the component is something that can be repaired or needs to be replaced. Often components that can be repaired may have a repair kit available from the manufacturer. If you have a leaking door seal, for example, you may be able to clean and, if appropriate, relubricate the seal. If it is damaged or worn, then replacement would be necessary.
The only temporary repairs that come to mind are, for example, a cracked weld or substituting a failed pump with a lower performing pump. For the cracked weld, you may discover that applying some vacuum-appropriate putty or similar material may help the furnace back to approvable vacuum capability. However, a repair like this should only be considered a temporary solution with plans to repair the weld at the earliest opportunity.
For a failed pump, you may replace it with another pump that might not have the same performance but is capable of the same vacuum level. While your process time might be slower, at least you can continue producing product until appropriate repairs can be made to the failed pump or you can replace it with the same type of pump.
Importance of Leak Detection
A leak on a vacuum system introduces air, thereby affecting the quality of the product or even ability to reach the process vacuum level. To ensure the quality of heat treated parts and prevent long delays in production, it is critical that heat treat operations with vacuum furnaces are well-versed in their equipment and leak detection resources, whether they own and operate helium leak detectors or hire a manufacturer or a third-party service company to detect and repair leaks.
About The Author:
Dave Deiwert President Tracer Gas Technologies
Dave Deiwert has over 35 years of technical experience in industrial leak detection gained from his time at Vacuum Instruments Corp., Agilent Vacuum Technologies (Varian Vacuum), Edwards Vacuum, and Pfeiffer Vacuum. He leverages this experience by providing leak detection and vacuum technology training and consulting services as the owner and president of Tracer Gas Technologies. Dave is a Heat Treat Consultant. Click here for more about Dave and other consultantsHeat Treat Today consultants.
In each installment of Combustion Corner, Jim Roberts, president of U.S. Ignition, reinforces the goal of the series: providing informative content to “furnace guys” about the world of combustion. The previous column examined the air supply inlet — the inhale, and this month, Jim is examining the exhaust system — the exhale, and how to inspect it, maintain it, and manage it.
This informative piece was first released in Heat Treat Today’sMarch 2025 Aerospace print edition.
A guy walks into a room full of furnace guys and says, “Is it just me, or is it a tad stuffy in here?”
We have all been able to imagine that it is hard to focus and do your job in an environment where it seems like it’s hard to breathe. Well, our hard workin’ buddy, the furnace, is continually stuck in a cycle of trying to breathe in, breathe out — and then somewhere in between, the magic of combustion and heat happens! We talked last month about the “breathe in” part of the combustion process. This month, we are going to remind you that if you take a really good, productive, inhaled, life giving breath, you are probably going to want to exhale at some point, too!
Tip 2: Ensure Exhaust Systems Are Properly Functioning and Clean
Inhale, exhale. It makes sense that if we were earlier having issues with the air supply inlet, the exhaust should also be checked. Today’s combustion equipment is sophisticated and sensitive to pressure fluctuations. If the exhaust is restricted, the burners will struggle to get the proper input to the process. I used to use the example of trying to spit into a soda bottle. Try it. It’s tough to do and invariably will not leave you happy. Clean exhaust also minimizes any chance of fire. Read on for three examples.
A. Check the Flues and Exhausts for Soot
If you are responsible for burners that are delivering indirect heat (in other words, radiant tubes), you have a relatively easy task ahead to check the flues/exhausts. Each burner usually has its own exhaust, and one can see if the burners are running with fuel-rich condition (soot/carbon). Soot is not a sign of properly running burners and will signal trouble ahead. Soot can degrade the alloys at a chemical level. Soot can catch fire and create a hot spot in the tubes. Soot obviously signals you are using more fuel than needed (or your combustion blower is blocked, see the first column in this series).
As a furnace operator or floor person, it should be normal operating procedure to look for leakage around door seals.
Here’s a sub tip: If you cannot see the exhaust outlets directly, look around the floor and on the roof of the furnace up by the exhaust outlets. Light chunks of black stuff is what is being ejected into the room when it breaks free from the burner guts (if it can). That will tell you it’s time to tune those burners. If you do not have a good oxygen/flue gas analyzer, get one. It can be pricey, but it will pay for itself in a matter of months in both maintenance and fuel savings.
B. Seriously … Check the Flues and Leakage Around Door Seals
If you are running direct-fired furnace equipment, or furnaces that have the flue gases mixed from multiple burners, it gets a little trickier. All the same rules apply for not wanting soot. Only now, it can actually get exposure to your product, it can saturate your refractory, and it can clog a flue to the point that furnace pressure is affected. An increase in furnace pressure can test the integrity of your door seals. It can back up into the burners and put undue and untimely wear and tear on burner nozzles, ignitors, flame safety equipment, etc. As a furnace operator or floor person, it should be normal operating procedure to look for leakage around door seals.
C. Utilize Combustion Service Companies
Ask the wizards. Combustion service companies can usually help you diagnose and verify flue issues if you suspect they exist. It’s always a great idea to set a baseline for your combustion settings. Service companies can help you establish the optimum running conditions. Again, money well spent to optimize the performance of your furnaces. I’m sure you already have a combustion service team; some are listed in this publication. Otherwise, consult the trade groups like MTI and IHEA for recommended suppliers of that valuable service.
Check flues monthly. It should be a regular walk around maintenance check.
Don’t let the next headline be your plant. See you next issue.
About The Author:
Jim Roberts President US Ignition
Jim Roberts, president at US Ignition, began his 45-year career in the burner and heat recovery industry directed for heat treating specifically in 1979. He worked for and helped start up WB Combustion in Hales Corners, Wisconsin. In 1985 he joined Eclipse Engineering in Rockford, IL, specializing in heat treating-related combustion equipment/burners. Inducted into the American Gas Association’s Hall of Flame for service in training gas company field managers, Jim is a former president of MTI and has contributed to countless seminars on fuel reduction and combustion-related practices.
