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.
Contact us with your Reader Feedback!
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.
In this Heat TreatRadioepisode, host Doug Glennsits down with Fernando Carminholi, the business development manager at Hubbard-Hall, to discuss solvent and aqueous cleaners and why cleaning is a crucial step in both pre and post thermal processing to ensure quality part outcomes. Fernando offers practical guidance, discusses solvent vs. aqueous cleaning methods, common pitfalls, and upcoming EPA regulations that could impact the industry.
From production to engineering to quality, there are valuable insights for everyone on optimizing cleaning process for better part quality, longer furnace life, and maintaining compliance in the latest regulatory environment.
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.
Doug Glenn:Welcome toHeat TreatRadio.I would like to start off with some parts cleaning basics. Do all parts need to be heat treated? Why do we do cleaning? And what are the risks of not cleaning?
General Parts Cleaning (01:40)
Fernando Carminholi: Thank you for this opportunity to talk about cleaners and the importance of cleaning. We’re going to focus on the cleaning before the heat treat, but there is also a cleaner after the heat treat when you remove quenching agents.
You asked how to know if parts need to be cleaned. And my answer to that is “yes,” and it could be “maybe” as well. The “maybe” is because some really light oily parts with light oil go to the furnace and there is not a problem. I would say that maybe 10% of all the parts heat treated do not need cleaned in any kind of operation. They go from stamping or deep drawing straight to the furnace.
But the rest — the 90% — will require cleaning. And that’s exactly what we’re going to talk about today.
Approximately 30%–35% will pass through a solvent cleaning. When we’re talking about solvent cleaning, there are two different ways to clean parts. One is the well-known technology of open-top degreasers. You have your solvent in a proper tank, and then you have some chillers on top to hold the vapor; this is called a “vapor degreaser.” You see a lot of these machines on the market from the 80s and 90s.
Another way to use solvents is in a closed vacuum machine, which is a more technologically updated machine.
And the rest of parts, I would say more than 50%, are cleaned in water-based cleaners, which could be in a spray application, a spiral tunnel, or immersion.
And normally, what kind of oils do we clean? As the years go on, there are new regulations for the oils with all the modernization. Every year the R&Ds work with new kinds of oils — cooling fluids, rust inhibitors, forming lubricants, and deep drawing compounds. Plus, they could be synthetic, and every year the oils become more difficult to remove. That’s the big challenge for the cleaning operation.
Doug Glenn: I assume the solvents must keep up with the changes in the chemistry of the cleaners?
Fernando Carminholi: Sure. Both of the systems have to keep up: the solvents and the aqueous.
Doug Glenn: If I’m hearing you right, Fernando, you’re saying that probably 90% of parts in in the heat treat process are cleaned. Maybe 35% of those get solvent-based cleaning and the rest aqueous-based.
I’ve heard that there are various reasons why we clean. Obviously if you’re going into a vacuum furnace, there are different reasons for why you clean than if you’re going into an air and atmosphere furnace. You’re wanting to make sure you don’t drag all those contaminants into a vacuum furnace. That’s one reason why you clean, right?
Fernando Carminholi: Exactly. But most will be more atmospheric furnaces. And then what do you drag in? Most of the clients we’re talking about move high volumes inside the furnace.
Let’s think about it in two different ways. If you don’t clean at all, or you have a bad cleaning, what is the problem? If you don’t have a cleaner at all because it’s a really light, clean oil and part that doesn’t drag that much oil, it could be fine.
But let’s think about a big operation with lots of oil, maybe fasteners or a kind of part that carries more oil to the furnace; it will produce a lot of drag and it will burn. You will have furnace contamination that will contaminate the oxygen and the carbon — it can cause decarbonization which can affect the hardness and the mechanical properties of the parts. The easiest way to see that this is happening is if there is a lot of smoke, which is common.
Fasteners that may carry more oil to the furnace
Doug Glenn: It is common. And one thought I had is not only will it potentially affect the parts, but it can impact the life of your furnace because you’re getting a lot of contamination, it’s going to need more maintenance, and you can damage your furnace.
Fernando Carminholi: Definitely. It will need more maintenance and shorten the life of the furnace. The smoke can also cause an uneven heat distribution inside the furnace and can lead to warping, cracks, and inconsistent hardness on the part. And that’s the result of no cleaning at all.
Now look at it another way. If you have the cleaner, machine-cleaning solvents or water based, and somehow you’re not cleaning the parts well, you can drag more than oil to the furnace. You can drag other compounds. With water-based cleaners in particular, you can drag the rinses together with all the chemicals.
And you have a different areas, like in nitriding or FNC operations, where the area with the oil that was not cleaned well will suffer some soft spots and unformed hardness — like the opposite of using sunscreen on the beach. You can cause surface defects like heating stains and areas that are well heat treated as well as areas where the structure is not as expected.
Doug Glenn: It’s almost like unintentionally using a stop-off paint on your part.
I want people who may not have dealt with parts cleaning in the past to hear some of these things: Not all parts need cleaned. A good number of parts do. If oil on the surface, or contamination, or spottiness on the finish of the part is not an issue, then you may not need to wash. But a very large percentage of parts that are heat treated do get washed in either solvents or aqueous-based, water-based solvents. And it’s good for the life of your furnace, the interior furnace, the maintenance of your furnace, and the properties of the parts.
Legislation (11:40)
I want to move on to a second topic that I thought would be very enlightening to some of our more experienced parts cleaning people. That is the area of legislation that Hubbard-Hall is aware of that’s going to be coming down the pike that we need to be aware of. Can you talk a little bit about the legislation regarding parts cleaning?
Fernando Carminholi: When we’re talking about legislation, everything that the EPA stated, let’s separate again into two different topics: water based and solvent based. When we’re talking about water-based cleaners, you have to watch out for what kind of raw materials you’re using.
What is the cleaner formulation? Because if you don’t rinse well, that’s something that you need to control in your process. If you don’t rinse well, you’re going to be dragging a lot of those materials. That can cause all the problems that we’ve already talked about. But legislation for water-based cleaners is less problematic.
I would like to wave a red flag right now because if you’re working with some product that will be restricted, you need to change.
And then, for example, you have some restrictions with some surfactants. And it’s based, but, for example, none of the latest. All those new formulations, I would say that they’re already free of.
Another big topic to discuss, and something that everyone is talking about now, is products containing PFAS. It could be in both a water-based cleaner and in the solvent.
Doug Glenn: What are those two things that you mentioned?
Fernando Carminholi: PFAS are fluorinated compounds. You see a lot of these in Teflon based, fire extinguisher foam, and in a lot of different things in the industry. These are forever chemicals. So far there is not a good, stable way to treat and eliminate these chemicals from the drinking water. This is something that the industry is regulating: how to treat and how to waste those chemicals because some of those compounds.
We’re talking about PPT (part per trillion); it’s a really low amount in the drinking water. But this is something to watch out for on the chemicals. This is something that is already suffering restriction, and it’s a hot topic.
Doug Glenn: Are these rules that are coming down federally based or are they state based?
Fernando Carminholi: These are federal. If you look up PFAS, all the surface finishing world and the wastewater world is talking about them. If you look at Congress, a lot of regulations from the government are talking about maybe having different states with different numbers. This is something that is already defining the rules and defining how to analyze and how to treat it.
Hubbard-Hall already does PFAS-free manufacturing. We decided not to work in this way.
I would like to switch gears a little bit here. With regulations, normally we talk more about the solvents. The solvents we’re talking about — methylene chloride, TCE (trichloroethylene), perchloroethylene, propyl mide — are the halogenated solvents that are already on the list. The EPA is working on this already.
I have a cheat sheet with some numbers I would like to bring up. If you go on the Hubbard-Hall website, you can find this table. To create this chart, we took all the regulations and put them in one table for different solvents. When the EPA rule was stated, for example, methylene chloride is already finishing. The rule was dated March 2024. All companies have until March 2026 to stop using this solvent as a cleaner.
Click the image for more information
There are exceptions. For example, if you use them for NASA or federal use, you have a little bit more time. For TCE, you have less than one year; by January 2026th, you’re not going to be able to use TCE as a vapor degreaser.
There are some alternatives for that. If you’re using an open-top machine, fluorinated solvents are an alternative; they have low global warming potential and are non-flammable, stable products. Those are available on the market.
Another alternative is modified alcohol, which is the best choice. This is a formulated alcohol. It’s not a book solvent. It’s a formulated product. It has a good cleaning ability and a good permeability because that’s the beauty of the solvent. It can go between the parts or inside the holes to clean everything. And modified alcohols can be used in the vacuum cleaning machine. It will work almost the same as the vacuum furnace. But on the cleaning side you have all the equipment running in a vacuum and you have a distillation process that will remove oil and the water from the part.
Doug Glenn: I’m curious about that chart that we were looking at. As you know, most of our readers and listeners are manufacturers who have their own in-house heat treating and we get a lot of commercial heat treaters, too. But our core audience are those manufacturers who have their own in-house heat treat. How many of them do you think are using either solvent or water-based solutions that are going to be ruled out by these regulations?
Fernando Carminholi: I would say that today 20% use halogenated solvents that need to be ruled out and switched for another technology. In some states, such as New York and Minnesota, this is already in place. They cannot use them. But the final date rule to be enacted, for example, for TCE would be January of 2026.
The unique one that is just proposed but is not finalized yet is the NPB. I think that will take between 3–5 years to be fully restricted.
Doug Glenn: It seems safe to say that there’s a significant number of people out there currently using cleaning solvents that will be outlawed over the next 3–5 years, so they need to start looking for another technology?
Fernando Carminholi: I would like to wave a red flag right now because if you’re working with some product that will be restricted, you need to change. Or use the same equipment. But as I told you, the fluorinated solvent would be 3–4 times more expensive.
On the other hand, if you’re going to buy equipment to use modified alcohol, there are not that many equipment manufacturers and that’s the limit. If 20% of this market needs to change, they will expect to change six months before. I would say that today you have equipment manufacturing expecting to deliver equipment in six months.
Doug Glenn: People need to keep in mind the lead time that they’re not going to get that equipment that quickly.
Aqueous Based vs. Solvent Cleaners (25:07)
Doug Glenn: Let’s jump in and talk about the pros and cons of using aqueous (or water-based) versus solvent cleaners. What’s the difference and why would we choose one over the other?
Fernando Carminholi: This is a really extensive debate. You can see some videos at the Hubbard-Hall website talking about this. What I see in the market is that companies selling only solvent will always talk poorly about the water-based. Companies that sell only water-based products are talking bad about the solvents and regulations.
I would say that Hubbard-Hall plays on both sides. We understand the best usage for different applications. I would try to go on the really high level. “Hey, I am the solvent side; I need to keep on the solvent side.” Or, “I need to go for a water based.”
First of all, you need to understand the contamination. What kind of oil? We’re talking about the cooling fluid, rust inhibitor, dip drawing, a lot of heavy, chlorinated oil, whether it contains sulfur, or whether it is a polar or nonpolar-based — that would decide what kind of solvent or water-based product you’re going to use. Normally, when you have an oil-based hydrocarbon, it tends to be easier to remove with solvents. When you have a water-based cooling agent or rust inhibitor, that’s easier to remove with a water base. This is one thing to consider, but it doesn’t mean that if you have a hydrocarbon you cannot remove it with water.
A discussion about waste and cost of parts cleaning
Another thing that you need to take a look at is the part geometry. If it is a flat part, it’s easy to remove oils with a spray. Or you may need ultrasonics to remove oils if there are a lot of blind holes and parts really close to each other. That’s an advantage of going to the solvents here because even if you use a really good surfactant, which will change the surface tension, the solvent tends to have a much better permeability — that’s the term for cleaning the really deep holes and the parts really close to each other.
Another thing to consider is I would call overall the EHS. That means what is the company? Is it okay to use inside the factory? Do I need VOCs? Do I need aqueous to be VOC free? For solvents you need to check how flammable they are.
Waste in Cleaning (29:07)
When we’re talking about waste and footprint — what is the difference between the systems? The footprint for solvent is smaller because all you need is the degreaser machine, open top or vacuum cleaner. You clean and you dry. Normally, the drying process is way easier with the solvent.
Plus, you don’t have all the other processes needed for the water based. All the waste generated from the solvent that you have is possibly some water that came from the water-based rust inhibitor or even the oil or some cleaner that is already gone. You have this weighed and then you send for a partner that will pick it up and take care of the waste.
For aqueous, this is different. You will need rinses. You will need a temperature to dry. You need blowers; you need heaters. The o-rings [ET1] may be needed to dry the parts, and that’s a problem. If you leave the water behind, it can lead to corrosion, for example. So that’s a big difference between solvent and water-based.
Doug Glenn: The reason the solvent is not an issue so much with the drag out, where you keep part of the cleaning solution on the products, is because of evaporation? Solvents evaporate much quicker than water.
Fernando Carminholi: Yes, that’s right. That’s why old open-top vapor machines could be a problem because the EPA [MS2][JM3] tightens limits every year. When you have an old machine with chillers on the top, you have the vapor phase, which is when you heat up your solvent. And then you have the chillers, which is the coil to condensate back. If the chiller is not working well, the solvency will go to the atmosphere. At the end, when you take out your part, it will dry up really easily. When you go for the closed system, you don’t have this emission.
That is another big difference between solvent and water-based. When you have a machine based on the solvent, you feel the machine. Normally, we’re talking about five to ten drums of product, and the consumption is really low. Clients spend one drum every 2 or 3 months for solvent depending on the system. For aqueous, you need all the rinses. So every time that you run a load, you go through the rinse, and you drag solution out of your tank, so the consumption will be higher for water based.
The Cost Debate (33:07)
Doug Glenn: So as far as variable cost, your aqueous system might have a higher operational cost?
Fernando Carminholi: That’s another good debate. The operational costs need to include the equipment as well.
Doug Glenn: I was going to ask about the difference between capital equipment costs. You said the solvent is a smaller footprint, does that mean it is a lower price?
Fernando Carminholi: Yes, I would say for the aqueous, if you need to include ultrasonic, for example, because you need an invasive way to use the waves to clean the parts, it will increase the cost. However, normally the cycles for the water based are lower. You can produce more parts.
No clear winner here when talking about cost
For example, if you were cleaning parts in a plant that already has a wastewater system, you will need to treat the water (possibly 1 to 2 gallons per minute depending on the flow rate on the rinses). This water needs to be treated before it is dumped into the sewage. You also need to follow the regulations and the limits.
But the cost overall depends on the parts. If we start to talk about cost, there’s a big difference now. Not that long ago, before Covid, water used to be cheap. But now water is very expensive. Energy is very expensive. Waste is very, very, very expensive. Then if you take all this rework, it is unacceptable. We like to say, cleaners can be cheap, but poor cleaning is always expensive.
The cleaning process will be cheaper than the heat treated part or even the steel or grinding or blasting. If you take the overall cost, cleaning is nothing. But if you don’t do the best that you can do, it can cause a huge problem, and that’s one thing to keep in mind.
Doug Glenn: Product failure, most notably. The more critical the part, the more important to make sure it’s cleaned.
Is it safe to say there’s no clear winner here when we talk about cost of equipment versus cost of operation for aqueous or solvent?
Fernando Carminholi: It really depends on the parts, the level of cleanliness that you want, and the kind of oil you’re using.
If you have a part that cannot be cleaned with aqueous because there’s a lot of holes and you need to clean inside the holes or the parts are close together, then there is no comparison. But you can bring up a lot of factors and put them side-by-side.
Solvent could be more expensive because of the chemical consumption, but for aqueous you need more equipment. When you’re talking about a vacuum cleaning machine, it will be a substantial capital expense for the equipment — over $1 million.
I’m seeing equipment manufacturers for the vacuum washing machine. They’re looking at the market and they see the problem of the mix of oils and cooling and you can use what they call a hybrid system. On the same machine you can use water-based fluid and then go to the solvent fluid. That’s a new feature in the market.
Doug Glenn: That’s very interesting. It’s a hybrid piece of equipment that starts with an aqueous wash and then finishes up maybe with a solvent washer?
Fernando Carminholi: Exactly.
Cleaning and the Environment (39:03)
Doug Glenn: Let’s move on to the fourth and final topic. I want to wrap up this third thing that we’re talking about as far as the pros and cons of aqueous versus solvent. If a listener has questions about which system makes the most sense for them, I’m sure your team at Hubbard-Hall can help them answer that question.
Fernando Carminholi: The best way to evaluate is to get a picture of your situation. We look at your costs, the pros and cons that you have today, your timeline for changing, whether you’re solvent regulated, for example.
We can do a scenario on how much you’re going to spend on the new line if you need a new line. We do have a prototype line where we can run some tests, different cleaners or solvent, or open-top machine. We can run different scenarios, evaluate the costs, and find a more environmentally friendly solution.
Doug Glenn: The last question I do want to ask you is about the cleaning process. How do we make it more efficient, profitable, and environmentally friendly?
Fernando Carminholi: The chemical manufacturers look it up in different ways. Let’s start with the solvent. Like I told you, there are a few. It’s a really low drag out. But it is dependent on the solvent, especially talking about modified alcohol. All the oil that you bring on the part could contain product that would change the pH of the chemical, and it could go really acidic or it could go really alkaline. That will screw up your machine; that will attack your parts. So, you lost the solution. You can have problems with the seal casket. You can attack the parts if you go acidic.
There are some ways to extend the life, and then you can analyze the solvent. You can add some stabilizers to continuously use the same solution because this is a fairly new technology. About ten years ago, the chemical manufacturers developed way better stabilizers to handle these new kinds of oil that we mentioned to extend the shelf life or the life of the solvent as much as we can. That’s a big savings.
On the aqueous side, what can be done? The problem here is why you dump your process. It’s because oil as well. Hubbard-Hall does work with a feature that’s a piece of equipment that is a membrane filtration. We built this equipment internally. We have sold it to many clients already. This technology has been on the market for 40 years; it’s well tested. This technology filters the oil out of the cleaner to extend the life of the cleaner.
I will give one example. We have a client with parts that are brake calipers. They need to dump the cleaners every 2–3 weeks. That’s a cost to put chemicals is a cost to treat. With the membrane filtration, it’s been more than five years without dumping the solution.
We understand that it recovers like 98% of the cleaner in the future oil that you don’t need. This changes the cost a lot. That’s why there are a lot of variables that we can put on the equation. That’s why I ask listeners with this problem that if you’re looking for the solution, we’re more than happy to jump in and evaluate one system or another and compare costs for what you have.
Doug Glenn: Does that membrane filtration system you’re talking about work on both solvent and water based?
Fernando Carminholi: No, normally the solvent has the distillation process to separate the solvent, the water, and the oil.
The main drain will work only on the water based and when you use product that will emulsify the oil. And emulsifying means the cleaner is able to mix the oil and the water like you see in milk when you have 2% of fat.
Doug Glenn: All right. Well, Fernando, I really appreciate your time and your being here.
Fernando Carminholi: Thank you for this opportunity. I hope that all the subscribers understand a little bit more clearly how important the cleaning process is before the heat treat.
About The Guest
Fernando Carminholi Business Development Manager Hubbard-Hall
Fernando Carminholi is the business development manager at Hubbard-Hall, a six-generation family business that develops, services, and supplies specialty chemicals for ferrous and non-ferrous metals. A chemical engineer graduate from E.S.P.M. in Sao Paulo, Brazil, he oversees the company’s distribution channels and business development team. Fernando has extensive experience in the chemical specialty products industry for surface finishing, focusing on industrial parts cleaning, metal pre-treatment, and functional electroplating.
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’sMarch 2025 Aerospace Heat Treating print edition.
Last time (Air & Atmosphere Heat Treating, February 2025) we addressed the question of why normalizing is necessary. Here we look at the importance of a “still air” cool on the final result. Let’s learn more.
What Is a “Still Air” Cool?
Contact us with your Reader Feedback!
As we learned last month, the term “cooling in air” is associated with normalizing but poorly defined in the literature or in practice, either in terms of cooling rate or microstructural outcome. This lack of specificity has resulted not only in many different interpretations of what is needed, but in a great deal of variability in the final part microstructure.
By way of example, this writer has on multiple occasions asked what changes are made to car bottom furnace cycles where cars are pulled outside of the plant for “air cooling” (Figure 1). Questions such as, is the furnace opened and the car pulled out in inclement weather? And, is this practice done on a particularly windy day, or in a rain or snowstorm or when the temperature is below zero? An all-too-common response is, “Only if it isn’t raining ‘too hard’ or snowing ‘too much’; then, we wait a while.” No wonder part microstructures are often found to vary from part to part and load to load!
Most heat treaters agree, however, that normalizing is optimized by a cooling in “still air.” This term also hasn’t been clearly defined, but it will be here based on both an extensive survey of the literature and the most common heat treat practices. In Vacuum Heat Treatment, Volume II, I define a still air cool as: “Cooling at a rate of 40°F (22°C) per minute … to 1100°F (593°C) and then at a rate of 15°F–25°F (8°C–14°C) per minute from 1100°F (593°C) to 300°F (150°C). Any cooling rate can be used below 300°F (150°C).”
Typical car bottom normalizing furnace opening to the outside environment
In addition, many consider nitrogen gas quenching in a vacuum furnace at 1–2 bar pressure to be equivalent to a still air cool. But again, so many factors are involved that only properly positioned workload thermocouples can confirm the above cooling rates are being achieved.
Also, many use the term “air cooling” to differentiate the process from “air quenching,” “controlled cooling,” and “fan cooling.”
Recall from the previous installment of this column that any ambiguity with respect to cooling rate ought to be defined in engineering specifications and/or heat treat instructions so that the desired outcome of the process can be firmly established.
From the literature, several important observations will serve as cautionary reminders. In STEELS, George Krauss points out that: “Air cooling associated with normalizing produces a range of cooling rates depending on section size [and to some extent, load mass]. Heavier sections air cool at much lower cooling rates than do light sections because of the added time required for thermal conductivity to lower temperatures of central portions of the workpiece.”
George Totten’s work in Steel Heat Treatment indicates: “Cooling … usually occurs in air, and the actual cooling rate depends on the mass which is cooled.” He goes on to state:
After metalworking, forgings and rolled products are often given an annealing or normalizing heat treatment to reduce hardness so that the steel may be in the best condition for machining. These processes also reduce residual stress in the steel. Annealing and normalizing are terms used interchangeably, but they do have specific meaning. Both terms imply heating the steel above the transformation range. The difference lies in the cooling method. Annealing requires a slow [furnace] cooling rate, whereas normalized parts are cooled faster in still, room-temperature air. Annealing can be a lengthy process but produces relatively consistent results, where normalizing is much faster (and therefore favored from a cost point of view) but can lead to variable results depending on the position of the part in the batch and the variation of the section thickness in the part that is stress-relieved.
In “The Importance of Normalizing,” this writer offers the following caution: “It is important to remember that the mass of the part or the workload can have a significant influence on the cooling rate and thus on the resulting microstructure.”
Finally, Krauss again observes: “The British Steel Corporation atlas for cooling transformation (Ref. 13.7) establishes directly for many steels the effect of section size on microstructures produced by air cooling.” (Note: Interpretation of continuous cooling transformation (CCT) curves will be the subject of a future “Ask The Heat Treat Doctor” column.)
Since hardness is one of the most commonly used criteria to determine if a heat treat process has been successful, it should also be noted that one can usually predict the hardness of a properly normalized part by looking at the J40 value when Jominy data is available.
The Metallus (formerly TimkenSteel) “Practical Data for Metallurgists” provides an example of the type of data available to metallurgists and engineers to help define a required cooling rate for normalizing (Figure 2).
All literature references to normalizing agree (or infer) that the resultant microstructure produced plays a significant role in both the properties developed and their impact on subsequent operations.
Figure 2. Combined hardenability chart for normalized and austenitized SAE 4140 steel showing approximate still air cooling rates and resultant hardness (data based on a thermocouple located in the center of the bar diameter indicated)
Final Thoughts — The State of the Industry
It is all too common within the industry for some companies who wish to have normalizing performed on their products to specify only a hardness range on the engineering drawing or purchase order callout that is given to the heat treater.
Industry normalizing practice here in North America varies considerably from company to company. Normalizing instructions are sometimes, but not often enough, provided on either purchase orders, engineering drawings, or in specifications (industry standards or company-specific documents). These instructions range from, in the case of certain weldments, absolutely nothing (i.e., no hardness, microstructure, or mechanical properties) to referencing industry specifications (e.g., AMS2759/1) or specifying complete metallurgical and mechanical testing including hardness and microstructure.
Most commercial heat treaters often perform normalizing to client or industry specifications provided to them. Others prefer so-called “flow down” instructions in which the process recipe is provided to them. It is a common (and mistaken) belief that this removes the obligation of achieving a given set of mechanical or metallurgical properties even if they are called out by specification, drawing, or purchase order.
Also, the final mechanical properties that result from normalizing are seldom verified by the heat treater. Rather, a hardness value (or range) is reported, but hardness is not a fundamental material property, rather a composite value, one which is influenced by, for example, the yield strength, work hardening, true tensile strength, and modulus of elasticity of the material.
Krauss, George. STEELS: Processing, Structures, and Performance, ASM International, 2005.
Practical Data for Metallurgists, 17th ed. TimkenSteel, 2011
Totten, George E., ed. Steel Heat Treatment Handbook, vol. 2, 2nd ed., CRC Press, 2007.
About the Author
Dan Herring “The Heat Treat Doctor” The HERRING GROUP, Inc.
Dan Herring has been in the industry for over 50 years and has gained vast experience in fields that include materials science, engineering, metallurgy, new product research, and many other areas. He is the author of six books and over 700 technical articles.
As heat treating facilities strive for energy efficiency and reliability, investing in power improvements can move a company toward sustainable operations. In this Controls Cornerinstallment, Brian K. Turner of RoMan Manufacturing, Inc. compares real power factor and displacement power factor in the efficiency and electrical performance of vacuum furnaces.
En el contexto de los hornos de vacío, el factor de potencia real y el factor de potencia de desplazamiento son conceptos claves en relación a la eficiencia y el comportamiento tanto de la fuente de energía eléctrica como de la carga del horno. A continuación, una comparación entre los dos factores.
1. El factor de potencia real (PF, por sus siglas en inglés)
Definición: El factor de potencia real es la relación entre la potencia real (potencia activa, P, medida en vatios) y la potencia aparente (S, medida en voltamperios). Da cuenta tanto del desplazamiento de fase como de la distorsión armónica.
Relevancia para hornos de vacío:
Los hornos de vacío, en particular los que funcionan con calentamiento por inducción, con frecuencia generan cargas no lineales debido a la operación de la electrónica de potencia.
Las cargas no lineales conllevan armónicos que distorsionan la forma de onda de la corriente generando una disminución en el factor de potencia real.
Un bajo factor de potencia real es indicador de ineficiencia ya que el sistema se ve obligado a aumentar el consumo de potencia aparente para generar la potencia real que se requiere.
2. El factor de potencia de desplazamiento (DPF, por sus siglas en inglés)
Definición: El factor de potencia de desplazamiento es el coseno del ángulo (ϕ) entre dos componentes fundamentales: el voltaje y las formas de onda de la corriente.
Relevancia para hornos de vacío
En los hornos de vacío la esencia inductiva de los componentes (p.ej., los transformadores y las cargas inductivas) genera un factor de potencia de retardo que se ve reflejado en el DPF.
Un bajo factor de potencia de desplazamiento (es decir, con retardo importante) implica demandas significativas para el sistema en cuanto a potencia reactiva, lo que a su vez afecta el tamaño de los transformadores y del equipo de distribución de energía.
Tabla superior: DPF – Condiciones ideales
La forma de onda sinusoidal verde representa la corriente en un escenario con factor de desplazamiento de potencia ideal en el que interviene únicamente el desplazamiento de fase (ϕ) entre el voltaje (curva azul) y la corriente.
Las formas de onda se ven limpias y sinusoidales, indicando la ausencia de distorsión armónica.
Tabla inferior: PF — Con distorsión armónica
La forma de onda roja representa la corriente con la intervención de la distorsión armónica, situación típica de sistemas con cargas no lineales, caso de los hornos de vacío.
Esta distorsión genera una disminución en el factor de potencia real frente al factor de potencia de desplazamiento, aún cuando no se haya modificado la relación en la fase fundamental.
Formas de onda que permiten visualizar el DPF vs. el PF en relación a voltaje y corriente
Efecto sobre el tamaño de transformadores y transformadores de distribución
Aumento en la demanda de potencia aparente
Un factor de potencia real disminuido (debido a los armónicos) implica que el transformador deberá manejar una mayor potencia aparente (S) sin importar que la potencia real (P) no haya cambiado. Esto puede aumentar los costos de capital al requerir transformadores más grandes.
Estrés térmico
Los armónicos llevan a pérdidas adicionales (por las corrientes inducidas y la histéresis) generando el sobrecalentamiento de los transformadores y disminuyendo la eficiencia y duración de los mismos.
Regulación de voltaje
Los armónicos distorsionan la forma de onda del voltaje, lo que podría afectar los equipos sensibles y obligar al uso de transformadores capaces de regular de manera más precisa el voltaje.
Penalización por consumo energético
Los proveedores del servicio de energía muchas veces aplican sanciones por un bajo factor de potencia real, con lo que buscan incentivar a los usuarios a mejorar la calidad de la potencia mediante el uso de filtros armónicos o corrección del factor de potencia.
Conclusión
La revisión del factor de potencia en los hornos de vacío es de crítica importancia para lograr una mayor eficiencia y la reducción de los costos operativos. En su avance hacia la eficiencia y la fiabilidad energética, invertir en estas mejoras permitirá a las plantas de tratamiento térmico acercarse un paso más a la operatividad sostenible.
Traducido por: Shawna Blair
About the Author:
Brian Turner Sales Applications Engineer RoMan Manufacturing, Inc.
Brian K. Turner has been with RoMan Manufacturing, Inc., for more than 12 years. Most of that time has been spent managing the R&D Lab. In recent years, he has taken on the role as applications engineer, working with customers and their applications.
As heat treating facilities strive for energy efficiency and reliability, investing in power improvements can move a company toward sustainable operations. In this Controls Cornerinstallment, Brian K. Turner of RoMan Manufacturing, Inc. compares real power factor and displacement power factor in the efficiency and electrical performance of vacuum furnaces.
In the context of vacuum furnaces, real power factor and displacement power factor are key concepts related to the efficiency and electrical performance of the furnace’s power supply and load. Here’s a comparison:
1. Real Power Factor (PF)
Definition: Real power factor is the ratio of real power (active power, P, measured in watts) to apparent power (S, measured in volt-amperes). It considers both the phase displacement and harmonic distortion.
Relevance to Vacuum Furnaces:
Vacuum furnaces, especially those using induction heating, often generate nonlinear loads due to the operation of power electronics.
Nonlinear loads introduce harmonics, which distort the current waveform, reducing the real power factor.
A low real power factor indicates inefficiency, as the system draws more apparent power for a given amount of real power.
2. Displacement Power Factor (DPF)
Definition: Displacement power factor is the cosine of the angle (ϕ) between the fundamental components of voltage and current waveforms. It ignores harmonic distortion and considers only the phase displacement caused by inductive or capacitive loads.
Relevance to Vacuum Furnaces
In vacuum furnaces, the inductive nature of components (e.g., transformers and inductive loads) causes a lagging power factor, which is reflected in the DPF.
A poor displacement power factor (e.g., heavily lagging) means the system has significant reactive power demands, affecting the sizing of transformers and power distribution equipment.
The above waveforms illustrate the difference between displacement power factor (DPF) and real power factor (PF) as they relate to current and voltage:
Top Chart: DPF — Ideal Conditions
The green sinusoidal waveform represents the current in an ideal displacement power factor scenario, where only phase displacement (ϕ) exists between the voltage (blue curve) and current.
The waveforms are clean and sinusoidal, indicating no harmonic distortion.
Bottom Chart: PF — With Harmonic Distortion
The red waveform represents the current with added harmonic distortion, typical in systems with nonlinear loads, like vacuum furnaces.
This distortion causes the real power factor to drop compared to the displacement power factor, even if the fundamental phase relationship is the same.
Waveforms that illustrate DPF vs. PF as it relates to voltage and current
Effects on Transformer and Utility Transformer Sizing
Increased Apparent Power Demand
A lower real power factor (due to harmonics) means the transformer must handle higher apparent power (S), even if the real power (P) is unchanged.
This can necessitate larger transformers, increasing capital costs.
Thermal Stress
Harmonics lead to additional losses (eddy currents and hysteresis), causing transformers to overheat and reducing their efficiency and lifespan.
Voltage Regulation Issues
Harmonics distort the voltage waveform, which can affect sensitive equipment and require transformers with tighter voltage regulation capabilities.
Utility Penalties
Utilities often impose penalties for low real power factor, incentivizing users to improve power quality through harmonic filters or power factor correction.
Conclusion
Addressing power factor in vacuum furnaces is crucial for improving efficiency and reducing operational costs. As heat treating facilities strive for energy efficiency and reliability, investing in these improvements is a step toward sustainable operations.
About the Author:
Brian Turner Sales Applications Engineer RoMan Manufacturing, Inc.
Brian K. Turner has been with RoMan Manufacturing, Inc., for more than 12 years. Most of that time has been spent managing the R&D Lab. In recent years, he has taken on the role as applications engineer, working with customers and their applications.
For more information: Contact Brian at bturner@romanmfg.com.
