A retort furnace with an Inconel 602CA alloy retort has been shipped from Pennsylvania to a leading manufacturer of motor laminations, located in Midwestern U.S. The laminations are deployed for motors in various aerospace, military, automotive, medical and industrial fields.
L&L Special Furnace shipped the model XLC3348 XLC3348 which has an effective work zone of 23” x 23” x 36” and uniformity of ±15°F above 1,200°F. The control system includes one control loop along with six zones of heating volume that can be adjusted to achieve the required temperature gradients. The model XLC3348 satisfies all requirements for AMS2750F class 3 uniformity and type B instrumentation. The process gas lines are required copper refrigeration lines along with stainless steel to ensure a very low dew point in the process gasses.
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A producer of aluminum and aluminum alloy sheets for the automotive and aerospace industries has ordered two continuous heat treatment lines (No. 3 and No. 4) and one continuous process treatment line (No. 4) from a manufacturer with North American locations.
The Andritz Group will supplyShandong Nanshan Aluminum Col, Ltd, China with the engineering, equipment supply, supervision of erection, and commissioning of the complete lines, including the electrical and automation equipment. Start-up will take place in 2025. Shandong Nanshan Aluminum Co., Ltd has built the complete aluminum processing industrial chain in its region.
Wang Tao, director of the Nanshan production plant, commented, "technology, focusing on excellent aluminum process lines, and the extensive local network of experts and service specialists" were factors in the decision.
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In December 2022, the first HIP batch on Latin American soil was performed. The journey to success in HIP, as any HIP user will agree, is a bumpy road. What are the challenges that aerospace manufacturers with in house heat treating should be aware of when considering HIP processing? Learn how HT-MX Heat Treat & HIPing — the heat treater who ran the first HIP batch in Latin American history — navigated the transition from small tooling jobs to HIP processing for aerospace parts.
Read the English version of the article below, or find the Spanish translation when you click the flag above right!
This original content article, first published in English and Spanish translations, is found in Heat Treat Today's March Aerospace Heat Treatingprint edition.
Writing this story as the first Latin American company to offer Nadcap accredited hot isostatic pressing brings a flood of memories and images to mind. HT-MX’s beginnings were simple, but also filled with challenges, failures, and lessons. When the company began, we were certain that, though small, we were still a “heat treat plant” and not just a shop.
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Being located in Mexico means that there were large companies with headquarters located far away — potential customers — that would be deciding on their heat treat supplier close to their location. We worked hard to be and to present ourselves as being very professional. But a lesson soon learned was that achieving trust with partners takes a lot more than a good speech and a clean plant.
Unsurprisingly, the first jobs were simple tooling work, like quench and tempering tooling and carburizing gears. A junior engineer and I would drive around in my old hatch-back to local machine shops and pick up a small shaft or gear and bring it back to the plant. We would get so excited when we got the case depth right.
With minimal resources, we decided to complete quality control ourselves. We became friends with a quality manager from a local company, and he came over to help on weekends and after 6:00pm until the audit date came. His knowledge is still in use at HT-MX to this day. I remember celebrating with a “Carne Asada” (a Mexican style barbecue) when we finished that first audit, thinking we had just made a huge step forward, not realizing how far away we still were from our vision.
HT-MX Team
Source: HT-MX Heat Treat & HIPing
But as time passed, we turned our attention to the aerospace industry in Chihuahua, a city with four OEMs. We received the AS9100 certification and started working on Nadcap accreditation. This required time, but by then, a pretty strong engineering team was in action, and successfully obtained Nadcap accreditation in late 2019. Again, we celebrated with a Carne Asada, this time, with a better understanding on where we were and what future challenges we needed to face.
Taking On Hot Isostatic Pressing
HIP system at HT-MX
Source: HT-MX Heat Treat & HIPing
The pandemic hit. Boeing’s 737 Max crisis continued to impact the industry. Moving into aerospace was slow with limited volume, especially compared to what we had seen in the automotive and oil and gas industry. But by now, international companies were more willing to transfer heat treat operations to Mexican suppliers, and we were ready, beginning with running aluminum batches, precipitation hardening, annealing, and other standard processes. It was during this early start to serve the aerospace industry that we heard about hot isostatic pressing (HIP).
Around 2019 during an aerospace cluster event, an OEM with a local presence approached us with their HIP requirements. I had only heard of HIP, but I was immediately interested — until I found out how much one of those machines cost!
But good financing through government programs helped make this HIP project a reality. Timing was not the best, as the federal election in Mexico caused a temporary Mexican currency depreciation, handicapping the project at its beginning.
Getting the proper certifications and validations proved to be a long and complex process, too. Theoretically, we knew what to expect, in terms of getting the Nadcap checklist approved, but the reality was a little different. Gaining Nadcap certification slowly builds a certain culture into any company in its day-to-day activities. Translating that culture into a completely different business unit, new crew, and new process proved to bring its own challenges.
HIP Challenges: Pressure, Temperature, Thermocouples, and Argon Supply
Heat treating usually handles temperature, atmosphere control (or lack of), and regular traceability requirements. HIP, however, adds a few new dimensions to what we usually see: internal pressure, very high temperatures — up to 3632°F (2000°C) — and argon supply. It was the first time HT-MX dealt with a process that incorporated up to 30,000 psi and also used a lot of high purity argon.
Pressure has its own challenges, though the HIP press takes care of those challenges. Still, the internal workings on these kinds of presses are fundamentally different than that of a regular heat treat furnace. Yes, you need to heat it up, but apart from that, it’s not even a furnace but a press. Understanding how the machine works, what happens inside with all that pressure, how it affects the components undergoing hot isostatic pressing, and how it affects the baskets you’re using is a critical learning curve.
High temperatures change everything about running these types of cycles. We work with metals, which means temperatures range between 1832°F and 2372°F (1000°C and 1300°C). This has an impact on thermocouple selection, calibration, and more; with the company’s thermocouple product suppliers based in the U.S., this entails more challenges and extra costs. I have lost count on those urgent same-day trips to the border to retrieve critical spares in time. It’s an 800-km/498-mi roundtrip! We have fortunately found a great supplier that has offered the technical feedback we needed, and we have started to finally understand and control our thermocouple consumption. Although, I must be honest here, we still have a lot to learn in this aspect.
Then, there’s the argon supply. HT-MX never expected it to be a challenge, but it turns out getting the proper supplier — one that understands the requirements and is willing to work with you from validation to production — is key. You might be able to start your validation process using argon transported in gas containers but eventually you will need to switch to liquid argon. That proved to be more difficult than expected. There are not many projects requiring these kind of alliances locally. Getting the right supplier was key and more of a challenge than expected. And then came the lessons on efficiently using the liquid argon, avoiding excessive venting of the tank, and being all around smart with the HIP schedule. This has been a constant learning process, one that has high costs.
Final Hurdles: Certifications, Current Events, and Energy Costs
Once our company had the Nadcap certification, we still needed to get the OEM’s approval for the HIP process, then the approval for the specific version of the HIP process, and then the actual approval for the part numbers.
These approvals were handled by the headquarters’ engineering department and not locally. It was a time-consuming process, with several test runs, lab testing, multiple audits, visits, and more testing, etc. And while all of this was happening, we still had to design the operation, locate critical suppliers not available in Mexico, create alliances with suppliers, etc. Writing this down in a few lines makes it seem simpler and quicker than it really was.
Additionally, in instances like this, Mexican companies, especially small ones, face much more scrutiny than U.S. or European-based companies, and must prove themselves in every single step. It makes sense, even if it feels a little unfair, as HT-MX had no proven track record of high tech processes such as HIP. It does cost extra time, extra care, and sometimes extra testing, but it is the reality we face and we must overcome the extra hurdles.
While navigating HIP approval, the pandemic hit. Months later, the war in Europe began with significant impacts on the cost of energy. Our main clients were high volume and low margin, and with energy prices rising, our competitiveness began to diminish. To adapt and evolve, we decided to add some smaller furnaces for smaller parts, invest in training and increased sales efforts, and focus on AMS/Nadcap-based customers, letting go of major clients. Slowly, things began to turn around.
The First Official HIP Batch in Latin America History
In December 2022, HT-MX ran the first official HIP batch in Latin American history. It was a long time coming. I always thought that running that first batch would feel like reaching the Everest summit. When the day came, it just felt like reaching Everest’s base camp. We still have a long way to go to be truly an established HIP supplier. Now, it’s back to climbing and shooting for that summit, that summit that will perpetually precede the next summit.
There are still several challenges: stabilizing new processes and improving established ones. But I am confident we will move forward in this new stage. And I am so looking forward to the next Carne Asada.
About the Author: Humberto Ramos Fernández is a mechanical engineer with a master’s degree in Science and Technology Commercialization. He has over 14 years of industrial experience and is the founder and current CEO of HT-MX Heat Treat & HIPing, which specializes in Nadcap-certifi d controlled atmosphere heat treatments for the aerospace, automotive, and oil and gas industries. With customers ranging from OEMs to Tier 3, Mr. Ramos has ample experience in developing specific, high complexity secondary processes to the highest requirements.
En diciembre de 2022, se realizó la primera horneada de HIP en suelo latinoamericano. El camino hacia el éxito en HIP, como cualquier usuario de HIP estará de acuerdo, es un camino lleno de baches. ¿Cuáles son los desafíos que deben tener en cuenta los fabricantes aeroespaciales con tratamiento térmico interno al considerar el procesamiento HIP? Aprenda directamente de HT-MX Heat Treat & HIPing, un tratador térmico que ejecutó la primera horneada de HIP en la historia de Latinoamérica, cómo navegaron la transición desde trabajos pequeños de herramentales hasta el procesamiento HIP para piezas aeroespaciales.
Read the Spanish translation of this article in the version below, or see both the Spanish and the English translation of the piece where it was originally published: Heat Treat Today's March Aerospace Heat Treating print edition.
Si quisieras aportar otros datos interesantes relacionados con HIP, nuestros editores te invitan a compartirlos para ser publicados en línea en www.heattreattoday.com. Puedes hacerlos llegar a Bethany Leone al correo bethany@heattreattoday.com
De herramientas simples al tratamiento térmico aeroespacial
Humberto Ramos Fernández Founder and CEO HT-MX
Escribir esta historia de como llegamos a ser la primera compañía latinoamericana en ofrecer prensado isostático en caliente acreditado por NADCAP trae a la mente una avalancha de recuerdos e imágenes. Los comienzos de HT-MX fueron simples, pero también llenos de desafíos, fracasos y lecciones. Cuando comenzamos la compañía, estábamos seguros de que, aunque éramos pequeños, éramos una “planta de tratamiento térmico” y no solo un taller.
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Estando ubicados en México quiere decir que hay grandes plantas con corporativos lejos de aquis — clientes potenciales — que estarían decidiendo sobre su proveedor de tratamiento térmico lejos de nuestra ubicación. Trabajamos arduamente para ser y presentarnos como profesionales y confiables. Pero pronto aprendimos que lograr la confi anza con los clientes requiere mucho más que un buen discurso y una planta limpia.
Como era de esperar, los primeros trabajos fueron trabajos simples de herramentales, algunos templados y revenidos de herramentales y carburizado de engranes. Recuerdo como un ingeniero junior y yo dábamos la vuelta en mi viejo hatchback alrededor de talleres locales y recogíamos un pequeño eje o engranaje y lo llevábamos de regreso a la planta. Nos emocionábamos mucho cuando lográbamos la profundidad de capa correcta.
HT-MX Team Source: HT-MX Heat Treat & HIPing
Con recursos mínimos, decidimos implementar el sistema de calidad nosotros mismos. Nos hicimos amigos de un gerente de calidad de una empresa local, venía a ayudarnos los fines de semana o después de las 6:00 p.m. hasta que llegó la fecha de la auditoría. Su enseñanzas aún se usan en HT-MX hasta el día de hoy. Recuerdo celebrar con una “Carne Asada” cuando terminamos esa primera auditoría, pensando que habíamos dado un gran paso adelante, sin darme cuenta de lo lejos que aún estábamos de nuestra visión.
Con el tiempo, dirigimos nuestra atención a la industria aeroespacial en Chihuahua, una ciudad con cuatro OEMs. Recibimos la certificación AS9100 y comenzamos a trabajar en la acreditación NADCAP. Esto requirió tiempo, pero para entonces contábamos con un equipo de Ingenieros bastante sólido y obtuvimos con éxito la acreditación de NADCAP a finales de 2019. Nuevamente, celebramos con una Carne Asada, esta vez con una mejor comprensión de dónde estábamos y qué futuros desafíos tendríamos que enfrentar.
Entrándole al Prensado Isostático en Caliente
La pandemia llegó. La crisis del 737 Max de Boeing continuó afectando a la industria. Empezar en sector aeroespacial fue lento y con un volumen limitado, especialmente en comparación con lo que habíamos visto en la industria automotriz y de oil&gas. Pero para entonces, las empresas internacionales estaban más dispuestas a trasladar las operaciones de tratamiento térmico a proveedores mexicanos, y estábamos listos, comenzando a procesar aluminio, endurecimiento por precipitación, recocido y otros procesos estándar. Fue durante estos inicios en la industria aeroespacial que escuchamos hablar del prensado isostático en caliente (HIP) por primera vez.
Alrededor de 2019, durante un evento del Cluster Aeroespacial de Chihuahua, un OEM con presencia local se acercó a nosotros con sus requerimientos de HIP. No conocíamos mucho de HIP, pero de inmediato me interesé . . . ¡hasta que descubrí cuánto cuesta una de esas máquinas!
Pero un buen financiamiento a través de programas gubernamentales ayudó a hacer realidad este proyecto de HIP. El momento no fue el mejor, ya que las elecciones federales en México causaron una depreciación temporal de la moneda mexicana, lo que obstaculizó el proyecto al principio.
HIP system at HT-MX Source: HT-MX Heat Treat & HIPing
Obtener las certificaciones y validaciones adecuadas resultó ser un proceso largo y complejo también. Teóricamente, sabíamos qué esperar en términos de obtener la aprobación para el checklist de NADCAP, pero la realidad fue un poco diferente. Obtener la certifi cación de NADCAP construye lentamente una determinada cultura en cualquier empresa en sus actividades diarias. Traducir esa cultura a una unidad de negocio completamente diferente, con un nuevo equipo y un nuevo proceso, demostró traer sus propios desafíos.
Retos en el HIP: presión, temperatura, termopares y argon
El tratamiento térmico generalmente trata de temperatura, control de la atmósfera (o la falta de ella) y los requisitos regulares de trazabilidad. HIP, sin embargo, agrega algunas dimensiones nuevas a lo que normalmente vemos: presión interna, temperaturas muy altas, de hasta 3632°F (2000°C) y suministro de argón. Fue la primera vez que HT-MX lidiaba con un proceso que incorporaba hasta 30,000 psi y también usaba mucho argón de alta pureza.
La presión tiene sus propios desafíos, aunque la prensa de HIP se encarga de ellos. Aún así, el funcionamiento interno en este tipo de prensas es fundamentalmente diferente al de un horno de tratamiento térmico regular. Sí, necesitas calentarlo, pero aparte de eso, no es ni siquiera un horno, sino una prensa. Comprender cómo funciona la máquina, qué sucede dentro con toda esa presión, cómo afecta a los componentes sometidos a prensado isostático en caliente y cómo afecta a las canastas y fi xtures que estás utilizando, es una curva de aprendizaje crítica.
Las altas temperaturas cambian todo sobre el funcionamiento de estos tipos de ciclos. Trabajamos con metales, lo que significa que las temperaturas oscilan entre 1832°F y 2372°F (1000°C y 1300°C). Esto tiene un impacto en la selección de termopares, calibración y más; con los proveedores de termopar basados en EUA, esto implica más desafíos y costos adicionales. He perdido la cuenta cuantos viajes urgentes de ida y vuelta por refacciones a la frontera he hecho. ¡Es un viaje redondo de 800 km! Afortunadamente, hemos encontrado un gran proveedor que nos ha ofrecido la retroalimentación técnica que necesitábamos, y finalmente hemos comenzado a comprender y controlar nuestro consumo de termopares. Aunque, debo ser honesto aquí, todavía tenemos mucho que aprender en este aspecto.
Luego está el suministro de argón. En HT-MX nunca esperamos que fuera un desafío, pero resulta que conseguir el proveedor adecuado, un que entienda los requisitos y esté dispuesto a trabajar contigo desde la validación hasta la producción, es clave. Es posible que puedas iniciar tu proceso de validación usando argón transportado en contenedores de gas, pero eventualmente necesitarás cambiar a argón líquido. Eso resultó ser más difícil de lo esperado. No hay muchos proyectos que requieran este tipo de alianzas a nivel local. Conseguir el proveedor adecuado fue clave y resultó ser un desafío mayor de lo esperado. Y luego vinieron las lecciones sobre cómo utilizar eficientemente el argón líquido, evitar el excesivo venteo del tanque y ser inteligente con el calendario de HIP en general. Esto ha sido un proceso de aprendizaje constante, uno que tiene altos costos.
Últimos obstáculos: certificaciones, eventos globales y costos energéticos
Una vez que nuestra empresa obtuvo la certificación NADCAP, todavía necesitábamos la aprobación de los OEM para el proceso HIP, luego la aprobación para la versión específica del proceso HIP y luego la aprobación real para los números de parte.
Estas aprobaciones fueron manejadas por el departamento de ingeniería del corporativo y no localmente. Fue un proceso que consumió mucho tiempo, con varias pruebas, pruebas de laboratorio, múltiples auditorías, visitas y más pruebas, etc. Y mientras todo esto sucedía, todavía teníamos que diseñar la operación, localizar proveedores críticos que no estaban disponibles en México, crear alianzas con proveedores, etc. Escribir esto en pocas líneas parece más simple y rápido de lo que realmente fue.
Además, en casos como este, las empresas mexicanas, especialmente las pequeñas, enfrentan mucho más escrutinio que las empresas estadounidenses o europeas, y deben probarse en cada paso. Tiene sentido, aunque se siente un poco injusto, ya que HT-MX no tenía un historial comprobado de procesos de alta tecnología como HIP. Cuesta tiempo extra, cuidado adicional y a veces pruebas adicionales, pero es la realidad que enfrentamos y debemos superar los obstáculos adicionales.
Mientras navegábamos en la aprobación de HIP, llegó la pandemia. Meses después, comenzó la guerra en Europa con impactos significativos en el costo de la energía. Nuestros principales clientes eran de alto volumen y bajo margen, y con el aumento de los precios de la energía, nuestra competitividad comenzó a disminuir. Para adaptarnos y evolucionar, decidimos agregar algunos hornos más pequeños para piezas más pequeñas, invertir en capacitación y aumentar los esfuerzos de ventas y enfocarnos en clientes basados en AMS / NADCAP, dejando ir a clientes principales. Poco a poco, las cosas comenzaron a mejorar.
La Primera Horneada Ofi cial de HIP en la Historia de Latinoamérica
En diciembre de 2022, HT-MX llevó a cabo la primera horneada oficial de HIP en la historia de Latinoamérica. Tomo bastante tiempo. Siempre pensé que hacer esa primera horneada se sentiría como llegar a la cima del Everest. Cuando llegó el día, solo se sintió como llegar al campamento base del Everest. Todavía nos queda mucho camino por recorrer para ser realmente un proveedor de HIP establecido. Ahora, volvemos a escalar y apuntamos a esa cima, esa cima que perpetuamente precederá a la próxima cima.
Todavía hay varios desafíos: estabilizar nuevos procesos y mejorar los establecidos. Pero estoy seguro de que avanzaremos en esta nueva etapa. Y estoy muy emocionado por la próxima Carne Asada.
Acerca del Autor:Humberto Ramos Fernández es un ingeniero mecánico con una maestría en Ciencia. Tiene más de 14 años de experiencia industrial y es el fundador y actual CEO de HT-MX Heat Treat & HIPing, que se especializa en tratamientos térmicos de atmósfera controlada, con certifi cación NADCAP, para las industrias aeroespacial, automotriz y de petróleo y gas. Con clientes que van desde OEM hasta Tier 3, el Sr. Ramos tiene una amplia experiencia en el desarrollo de procesos secundarios específi cos de alta complejidad para los requisitos más exigentes.
A new, fully automated quenching system is nearing completion and will be installed at C/A Design’s heat treat facility in Exeter, NH, which serves the aerospace and defense industry. It has been custom designed and developed specifically to service aluminum brazing applications, expanding capabilities and services.
The system, from Wakefield Thermal, adheres to the guidelines set by both AMS2750 and AMS2770, ensuring proper heat treatment for aluminum brazements and adherence to critical specifications. The custom solution for C/A Design includes temperature and quenching control technology.
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What is the connection between AMS2750 specifications and furnace classifications? With tight specifications, what does the heat treater need to know to be compliant? Follow along as we take a brief look into this often-overlooked topic.
This Technical Tuesday article, written by Douglas Shuler, owner and lead auditor, Pyro Consulting LLC, was first published in Heat Treat Today's March 2023 Aerospace Heat Treating print edition.
Doug Shuler Lead Auditor Pyro Consulting
AMS2750 is the specification that covers pyrometric requirements for equipment used for the thermal processing of metallic materials. AMEC (Aerospace Metals Engineering Committee) is one of the committees which oversees the changes and revisions of AMS2750. There are five main sections in the technical requirements of the specification: sensors, instrument calibrations, thermal processing classification, SAT (system accuracy testing), and TUS (temperature uniformity surveys). Additionally, there are quality provisions that detail what happens if a calibration or test is either past due or fails.1
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Revisions to the original requirements have occurred over the years, with the newest being Revision G. The structure of Revision G has carried over from Revision F and has remained the current structure of the AMS2750 specification. This structure includes furnace classes, which are based on the minimum requirements for temperature uniformity.
Furnace classes are defined in Figure A of Revision D Figure 1.
Figure 1. AMS2750G furnace class uniformity tolerances Source: Doug Shuler
Originally, furnace classes were based on temperature uniformity, but also subzero transformation, refrigerated storage of aluminum alloys, and embrittlement relief, Figure 2.
Figure 2. Original AMS2750 instrument accuracy requirements, no class structure Source: Doug Shuler
AMS2750 Revision C was released in May 1990 and started to implement the class and instrumentation type structure and differentiated between furnaces for heat treating parts versus furnaces for heat treating raw materials. Furnaces for heat treating parts were classified based on uniformity, but also on a readability requirement. Furnaces for heat treating raw materials were classified based on a readability requirement alone.
AMS2750 Revision D was released in September 2005 and continued to define equipment class (Figure A)* and instrumentation type (Section 3.3.1.1)*. It also clarified chart recorder resolution (Table 4)*, print and chart speed (Table 5)*, and testing frequencies for SAT (Tables 6, 7)* and TUS (Tables 8, 9)* for the processing of parts versus raw materials.
AMS2750 Revision E was released in July 2012 and continued to build on the clarity presented in Revision D by adding an instrumentation type table (Figure 3)* instead of a simple text description in the body of the specification.
Figure 3. AMS2750 Revision C: distinguishment between furnaces for heat treating parts versus raw materials Source: Doug Shuler
Moving to AMS2750 Revision F, the specification saw a major rewrite and restructuring where the tables were moved from the end of the document to the first area text that called out the specific table. Revision F also put into place a sunset date for analog instruments.
That brings us to the current revision of AMS2750, Revision G, which has carried forward the structure of Revision F and only sought to further clarify the intent of the requirements.
Over the years, the technology of sensor, instrument, and furnace manufacture and capability has continued to produce better and tighter controls for the process of heat treating. The evolution of AMS2750 has recognized these advancements and has kept pace with them in technology. The understanding of the origins of AMS2750 and how it has evolved is vital in understanding its application to today’s heat treat special processes.
*Specified figure, table, or section is associated with the AMS2750 revision being discussed.
About the Author: In 2009, Douglas (Doug) Shuler became the owner of Pyro Consulting LLC and also began working with Performance Review Institute (PRI), first as an instructor and course developer and later as an auditor for the Nadcap program. As a lead auditor for Nadcap, he has conducted over 380 Nadcap special process and aerospace quality management system audits on behalf of the Aerospace Primes over the past 10+ years. Doug continues to focus on instruction, training, and education for the heat treat industry, developing courses, authoring exams, and employing the PIE method: “Procedures that Include all requirements, and Evidence to show compliance.”
Robert (Bob) Hill, President at Solar Atmospheres of Western PA Source: Solar Atmospheres
A western PA heat treater recently degassed 175,000 pounds of 6AI-4V titanium in their 48-foot-long vacuum furnace. This is the largest and heaviest single load of titanium ever processed in the company's history.
Solar Atmospheres of Western PA vacuum degassed the load consisting of 154 sheets of titanium 40” x 240”. Their president, Bob Hill, states, “The future of the global aerospace titanium market is very promising with the many opportunities in the commercial and military aircraft markets!”
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What are the factors that lead to carburization and carbon transmission? How can heat treater avoid these unwanted reactions? Discover the challenges of CFC fixtures and the steps heat treaters can take to mitigate these challenges.
This Technical Tuesday article, written by Dr. Jorg Demmel, founder, 0wner, and president, High Temperature Concept, was first published in Heat Treat Today's March 2023 Aerospace Heat Treating print edition.
Introduction
Dr. Jorg Demmel Founder, Owner, President High Temperature Concept
The main advantages of CFC fixtures were introduced in “CFC Fixture Advantages and Challenges in Vacuum Heat Treatment, Part 1,” which was released in Heat Treat Today’s November 2022 publication. This included a discussion of the limits of CFC in vacuum and protective atmosphere heat treatment. Successful applications of CFC workpiece carriers in heat treatment were presented along with field test results that included a brief discussion of undesired contact reactions (i.e., carburization and melting of parts). In Part 2 of this paper, the mechanisms involved with carburization and carbon transmission due to direct contact of parts with CFC fixtures will be further explained.
Mass Transfer from CFC Fixtures
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The mass transport of carbon from CFC fixtures into steel parts at high temperatures will be examined in the following areas:
Reactions in oxygen (i.e., the reaction medium)
Transport of carbon in CFC during exposure to oxygen
Transfer mechanism into the steel parts
Diffusion of carbon into the steel parts
Part reactions (melting, carbide formation)
Figure 1: 1.6582 steel samples and GDEOS depth profile analysis Source: Dr. Jorg Demmel, High Temperature Concept
CFC samples were tested in contact with steel samples under laboratory conditions in a vacuum of 7.5 x 10-7 Torr (1 x 10-6mbar). Results of the contact with CFC for steel samples at different temperatures are presented to the left (Figure 1). It is important to note that:
Sample (0) is the reference sample and had no exposure to the contact test.
Sample (0’) is the back side of Sample (0).
Sample (1) is the contact side at 1922°F (1050°C).
All three samples are visually identical, therefore only one is shown. Sample (2) at 1967°F (1075°C) and Sample (3) at 2012°F (1100°C) exhibited a distinct visual surface pattern after CFC contact. This was analyzed by Glow Discharge Optical Emission Spectroscopy (GDOES) and the test location (gray spot) clearly observed on Samples (2) and (3). For Sample (4) run at 2057°F (1125°C), the CFC was found to have adhered to the steel surface.
The carbon content in 10mm depth measured with GDOES (see the profiles in Figure 1) increased from initially 0.29 weight-% for the 1922°F (1050°C) test, although nothing was visible on metal surfaces. For carbon contents, see Table 1.
Table 1. Carburizing of 1.6582-samples in 10 µm depth after CX-27C1-contact (GDOES) Source: Dr. Jorg Demmel, High Temperature Concept
CFC Reactions with Oxygen
The chemical reactions of CFC with various gases are essential in Step 1 (referenced in Part 1 of this article) and an indicator of chemical thermal suitability.
In the case of the unwanted contact carburization considered above is similar, in a sense, to carburization of steel in contact with carbon powder or granulate. However, the actual carburization mechanism, which occurs between approximately 1616°F and 1697°F (880°C and 925°C), does not take place directly via the carbon contact but is based on the fact that solid carbon reacts with atmospheric oxygen according to the Equation Table to form carbon dioxide (CO2).
Equation Table. Reaction rates and activation energies for graphite (800°C; 0.1 bar) Source: Dr. Jorg Demmel, High Temperature Concept
Carbon monoxide (CO) is then formed from CO2 by the Boudouard reaction (Equation 3). At high temperatures and low pressures (see Figure 2), almost only CO is present.
Figure 2. Boudouard equilibrium Source: Dr. Jorg Demmel, High Temperature Concept
Transport of Carbon
The carbon carrier must be transported to the surface of the parts.
The cases considered in Part 1 of this article were conducted in vacuum, that is in the absence of a carburizing atmosphere. The laboratory tests were even carried out in a vacuum as low as 7.5 x 10-7 Torr (1 x 10-6mbar). Nevertheless, part surface reactions were observed.
Transfer Mechanism into the Steel Parts
Theoretically, carbon from the CFC fixtures can be transferred into the steel via solid phase (as opposed to gaseous phase) reactions. Gas particles can be adsorbed by surfaces via physisorption and/or chemisorption. The author’s personal research experience has shown that metal samples usually oxidize after a short time, even in a high vacuum of 7.5 x 10-7 Torr (1 x 10-6mbar). In particular, elements such as iron, molybdenum, and chromium have a strong ability to chemically adsorb oxygen or CO.
Furthermore, there is a disproportionately large amount of adsorbed oxygen in the CFC samples. CFC has open porosities as high as 30%. CFC in industrial practice is never completely evacuated. So, there is a disproportionately large amount of oxygen present in CFC fixtures.
It can be assumed that oxygen repeatedly escapes from the CFC and is initially available in the contact area. Proof of this can be provided by the GDOES analysis. Outside the contact areas, no (gas) carburization took place (as evidenced by the non-contact side of steel samples).
The oxygen and carbon surplus combined with close contact lead to complete reaction of oxygen creating carbon dioxide as in Equation (1). Because of the carbon surplus, almost only carbon monoxide is produced as shown in Equation (2). Because of the very close contact between CFC and steel, C-adsorption by gamma iron and desorption of carbon dioxide as in Equation (5) takes place:
Equation 5 Source: Dr. Jorg Demmel, High Temperature Concept
Since carbon dioxide immediately comes in contact with carbon in the CFC again, carbon monoxide is produced according to Equation (3). In other words, carbon dioxide regenerates immediately and the reaction starts again.
Direct carbon transfer from CFC to metal via solid phase is very unlikely since carbon atoms in CFC are firmly bound in rings.
Diffusion of Carbon in the Steel Parts
In solids, the surface diffusion usually takes place at significantly higher diffusion rates than in the bulk material. The thermodynamic driving force of diffusion or carburizing reactions is the difference in carbon activity for a specific concentration in the austenite to that of the reaction medium. The carbon activity is the ratio of the vapor pressure of the carbon in state under consideration to vapor pressure of pure carbon (graphite/CFC). Alloying elements of the steel influence the activity of the carbon.
Part Reactions (Melting and Carbide Formation)
Steel can begin to melt if, at the given values for temperature and pressure, a partially liquid phase is reached, that is, the solidus line in the phase diagram is exceeded. At even higher temperatures, the liquidus temperature can be reached and steel is completely liquid.
According to metastable iron-carbon diagram phase diagram (Figure 3), a steel such as SAE/ AISI 4340 (34CrNiMo6) alloy (DIN 1.6582) with around 0.47% by weight percent carbon does not begin to melt at 1922°F (1050°C), the exposure temperature for Sample (1), or Sample (2) at 0.56% and 1967°F (1050°C) for Sample (3) with 0.67% for 2012°F (1100°C). The iron-iron carbide phase diagram applies to steels with less than 5% (by mass) of alloying elements and thermodynamic equilibrium, so it is an accurate representation for a SAE/AISI 4340 (34CrNiMo6) alloy.
Figure 3. Metastable equilibrium diagram Fe-Fe3C for steel (good fit for 1.6582) Source: Dr. Jorg Demmel, High Temperature Concept
A calculation of the solidus temperature shown on the iron-iron carbide diagram (Figure 3), which is dependent on the carbon content and alloying elements, yields a value of 2703.2°F (1,484°C) (J’).
For an SAE/AISI 4340 (34CrNiMo6) steel (DIN 1.6582) with 0.3% C and one for 0.5% C, the calculated solidus temperature is 2640°F (1449°C). This is shown on the J’-E’ blue dotted line in Figure 3. In other words, a lower solidus line (cf. dashed blue line in Figure 3) and thus a slight reduction in austenite phase region.
The iron-carbon diagram also indicates that melting of surfaces that have absorbed carbon (e.g., Sample No. 2) will occur at 1967°F (1075°C). This value is within approximately 90°F (50°C) of the temperature used (dotted line E’-C’-F’). From this information we can conclude that the observations seen in Figure 1 are not the result of melting, but rather imprints due to surface softening.
The melting (c.f., Figure 1) observed in Test No. 4, which occurred at 2057°F (1125°C) is likely due to partial carburization of the steel surface and exceeding the solidus temperature. A micrograph confirms eutectic melting and high carbon content, which could also be indirectly confirmed by hardness measurement.
Carbide Formation
Additional reactions can occur between carbon absorbed from the CFC fixtures and the steel parts due to either separation of carbides (e.g., iron carbide in the form of secondary cementite) or carbide formation with alloying elements such as Ti, V, Mo, W, Cr, or Mn (listed in decreasing tendency to form carbides).
Table 2. Reactions between C and metal Source: Dr. Jorg Demmel, High Temperature Concept
Table 2 lists various elements in alphabetical order that react with carbon above the specified temperatures to form reaction products mentioned, primarily carbides. It should be noted that the temperatures listed apply only to pure metals and pure carbon. As such, they provide only rough approximations of a temperature at which a reaction might begin.
Countermeasures
There are several measures to avoid these unwanted reactions:
Ceramic oxide coatings such as aluminum oxide (Al2O3) or zirconium oxide (ZrO2) layers placed onto the CFC
Hybrid CFC fixtures having ceramics in key areas to avoid direct contact with metal workpieces
Alumina composite sheets
Boron nitride sprays
Special fixtures made of oxide ceramics
An yttrium-stabilized zirconium oxide layer (93/7) was applied to CF222 by thermal plasma spray and tested successfully (see Figure 4).
Figure 4. Yttrium-stabilized zirconium oxide layer with an average layer thickness of 110µm on CF222 material. The photograph on the right shows a hybrid CFC fixture. Source: GTD Technologie Deutschland
Summary
It is important to consider the specific process conditions in advance so that unwanted reactions — from carburization to catastrophic melting of the workpieces — can be avoided. Effective countermeasures can be taken.
References
Atkins, P. W.: Physikalische Chemie. 1. vollst. durechges. u. berichtigter Nachdr.d. 1. Aufl ., Weinheim, VCHVerlag, 1988 – ISBN 3-527-25913-9.
Bürgel, R.: Handbuch Hochtemperatur-Werksto technik: Grundlagen, Werksto bean-spruchungen, Hochtemperaturlegierungen. Braunschweig, Wiesbaden: Vieweg, 1998. ISBN 3-528-03107-7.
Demmel, J.: Advanced CFC-Fixture Applications, their scientific challenges and economic benefits, In: 30th Heat Treating Society Conference & Exposition, Detroit, MI, USA, 15th Oct. 2019.
Demmel, J.: Werkstoffwissenschaftliche Aspekte der Entwicklung neuartiger Werkstückträger für Hochtemperaturprozesse aus Faserverbundkeramik C/C und weiteren Hochtemperaturwerkstoffen, Dissertation, TU Freiberg, Germany, 2003.
Demmel, J.: Why CFC-Fixtures are a Must for Modern Heat Treaters, FNA 2020 Technical Session Processes & Quality, USA, 30th Sept. 2020.
Demmel, J., et al: Applications of CMC-racks for high temperature processes. In: 4th Int. Conf. on High-Temperature Ceramic Matrix Composites, 3.10.2001, p. A-17.
Demmel, J. und J. Esch: Handhabungs-Roboter sorgt für Wettbewerbsvorsprung. Härterei: Symbiose von neuen Werkstoffen und Automatisierung. In: Produktion (1996), No. 16, p. 9.
Demmel, J. und U. Nägele: CFC revolutioniert die Wärmebehandlung. In: 53. Härterei-Kolloquium, Wiesbaden, 10.10.97. Vortrag und Tagungsbericht.
Demmel, J., Lallinger, H.: CFC-Werkstückträger revolutionieren die Wärmebehandlung. In: Härtereitechnische Mitteilungen 54, No. 5, p. 289-294, 1999.
Eckstein, H.-J., et al: Technologie der Wärmebehandlung von Stahl. 2nd Edition, VEB Deutscher Verlag für Grundstoffindustrie, Leipzig, 1987. ISBN 3-342-00220-4.
Godziemba-Maliszewski, J.; Batfalsky, P.: Herstellung von Keramik-Metall-Verbindungen mit Diffusionsschweißverfahren. In: Technische Keramik, Jahrbuch, Essen, 1 (1988), S. 162-172. ISBN 3-80272141-1.
Grosch, J.: Grundlagen-Verfahren-Anwendungen-Eigenschaften einsatzgehärteter Gefüge und Bauteile, ExpertVerlag, 1994, ISBN 3-8169-0739-3.
Hollemann, A.F.; Wiberg, E.: Lehrbuch der anorganischen Chemie / Hollemann-Wiberg. 91.-100. Aufl ., de Druyter Verlag, 1985 – ISBN 3-11-007511-3.
Kriegesmann, J.: Technische Keramische Werkstoffe. Loseblattwerk mit 6 Ergänzungslieferungen pro Jahr.
Kussmaul, K.: Werkstoffkunde II. Stuttgart, Universität, Lehrstuhl für Materialprüfung, Werkstoffkunde und Festigkeitslehre, Vorlesungsmanuskript, 1993.
Lay, L.: Corrosion Resistance of Technical Ceramics. 1. Aufl ., Teddington, Middlesex, Crown-Verlag, 1983 – ISBN 0-11-480051-0.
Marsh, H.; u.a.: Introduction to Carbon Science. 1. Aufl ., London, Butterworths-Verlag, 1989 – ISBN 0-40803837-3.
Spur, G.: Wärmebehandeln. Berlin, 1987, ISBN 3-446-14954-6.
Samsonow, G.V.: Handbook of refractory compounds. New York, 1980.
Schulten, R.: Untersuchungen zum Kohlenstofftransportmit Carbidbildung in Nickelbasis-legierungen. RWTH Aachen, Fakultät für Maschinenbau, Diss., 1988 Deutsche Keramische Gesellschaft, 1990 following. ISBN 3-87156-091-X.
About the Author: Dr. Jorg Demmel is the founder, owner, and president of High Temperature Concept. He received his Engineering Doctorate in the field of CFC workpiece carriers for heat treatment and served in different leading positions for Volkswagen before moving to the U.S. In this article, Demmel draws on his dissertation, “Material scientific aspects of the development of new Fixtures for high temperature processes made of fiber-composite ceramics C/C and other high temperature materials” (Technical University Mining Academy Freiberg, Germany, 2002/3), and his personal experiences. For more information, contact Jorg at jorg.demmel@high-temperature-concept.com
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You can take the aircraft apart, but can you put it back together? Reverse engineering, as anyone who has ever taken apart the TV remote will tell you, is more complicated than it first appears. It is, however, far from impossible. Learn the essential steps to reverse engineering, the role of heat treating, and the challenges the thought process presents.
For this Technical Tuesday piece, take a few minutes to read Jonathan McKay's, heat treat manager at Thomas Instrument, article drawn from Heat Treat Today's March Aerospace Heat Treating print edition. Heat Treat Today is always pleased to share pieces from one of our 40 Under 40 alumnus like Jonathan!
If you want to share ideas about the aerospace industry, our editors would be interested in featuring it online at www.heattreattoday.com. Email Bethany Leone at bethany@heattreattoday.com with your own contributions!
Contact us with your Reader Feedback!Jonathan McKay
Heat Treat Manager at Thomas Instrument
Source: Thomas Instrument
Reverse engineering (RE) is the process of taking a component or design and dissecting it all the way down to the raw material. Reverse engineering can range from a singular component such as a piston or gear, to multiple components that make up an overall assembly such as an engine or mechanical actuator. This process allows engineers to analyze and gain an understanding of a component’s overall function and design through deductive reasoning. RE can range in the type of analysis, from geometric measurements and material analysis to electrical or mechanical testing. Each analysis reveals clues of how something can be reproduced. The idea of reverse engineering is to look beyond what’s in front of you and find the unexposed clues that can show why something was designed or possibly the thought process of the original designer.
Reverse engineering typically happens through a third-party manufacturer usually not affiliated with the original equipment manufacturer (OEM). Often this is done because the original manufacturer no longer supports the product, or the original design is outdated and needs to be modernized to improve efficiency, functionality, or life expectancy. To put this in perspective, the U.S. Airforce received its first B-1 Bomber in 1984. Since then, over 100 aircrafts have been delivered. After nearly 50 years the aircraft is still flying, but many OEM manufacturers have moved on to newer programs, thus allocating their capabilities and capacity towards the present and future market demands. This creates a market for fabrication of replacement components and assemblies to support aging platforms. In most cases, the OEM’s retain proprietary data thus creating a need for RE processing.
"[T]he U.S. Airforce received its first B-1 Bomber in 1984.
Source: Unsplash.com/midkiffaries
With aerospace products in particular and specifically aging aircrafts, one will encounter obsolescence issues. The goal is to maintain the aircraft with replacement parts that conform to all form, fit, and function requirements while also assuring they have proper life expectancy with respect to maintenance cycles. With this in mind, you typically work with low volume production and invest more time into the design and planning phase of the process. When engaged in this process, it is critical that one understands and implements a fabrication plan that will yield a product that is equivalent or better than that of the OEM. Some engineers would say “Well, let’s make it bigger and better,” but with aerospace components this is not always the case. Typically, the main focus is to replicate the original design intent to the best of your ability because you have a specific footprint and weight to maintain as well as functionality. The exchangeability of the original design and RE design is key. The reverse engineered product needs to possess the same functional and physical characteristics and be equivalent in the performance, reliability, and maintainability. This allows both items to be exchanged without concern for fi t, performance, or alterations to its adjoining component(s).
Another key point in RE processing could be to limit long lead phases by minimizing the need for additional qualification testing where possible. As plating, heat treat, or materials begin to deviate from the initial design, you must consider requalification testing to prove those changes are not detrimental to the application and do not cause more harm than good. Sometimes engineers create features within a design that are meant to be a weak point; this prevents a more critical component from breaking or being destroyed. When you begin to make deviations, it may push the weak point closer to the critical component.
While there are certainly many steps to RE, the essential steps include:
Collect as much data as possible from an external standpoint without destroying or disassembling; i.e., note the overall measurements, orientation, special features, electrical or mechanical properties, etc. It is also a good idea to analyze mating components and/or the system in which the component is utilized. Mating parts are a big part of the discovery; the mating parts can help determine what alternate materials, plating, heat treat, or finishes can be used.
Start creating preliminary drawings with detailed dimensions, notes, and features that were inspected from Step 1.
Slowly disassemble the part (if an assembly) and inspect key features and create preliminary drawings for sub-assembly components. In some cases, it helps to reassemble the product to ensure an understanding of how it goes back together in order to optimize the assembly process once new components are manufactured.
Evaluate the product(s). Conduct material analysis to acquire chemical and mechanical property data. This will aid in defining the appropriate layout for machining, material conditioning (i.e., heat treatment), external finishes/coatings, etc.
While the design and planning phase may pose some challenges, the more critical challenges that occur during reverse engineering are in the execution of the manufacturing, assembly, and qualification testing. To elaborate, once you begin machining and processing components, there may be special methods of manufacturing that require discovery because standard methods may not have worked when the OEM produced it. When this happens, you go back and forth on updating and fine-tuning the process plans, fixturing, programs, etc. Sometimes this means scrapping parts and starting over or validating if parts are still usable for prototyping. Along the same lines, when the process progresses into the assembly and testing phase, engineers typically discover variability, errors, or weak points that require adjustments. In those cases, the engineer’s drawings must be revised. A large percentage of these issues can be limited through experience with similar components or assemblies, but in most cases, there is a lot of analysis and some trial-and error involved in the manufacturing, assembly, and testing phase that is not apparent upon initial RE processing.
References:
Boeing. “The Bone.” https://www. boeing.com/defense/b-1b-bomber/
DLA. “Master List of Technical and Quality Requirements Version 14.”
MIL-STD-280A. “Handbook for definitions of item levels, item exchangeability, models, and related terms.”
DOD Washington, D.C. 20301.
Special thanks to David V. Jones and Thomas R. Blackburn IV at Thomas Instrument for their input on this topic.
About the Author:
Jonathan McKay is a mechanical engineer at Thomas Instrument, a company specializing in reverse engineering critical aerospace components. At the company, he is manning the establishment of heat treat operations, has created procedures and process plans for Thomas Instrument to be an approved heat treater for an aerospace prime, and has attained Nadcap accreditation for heat treat.
Aero Space Power, an MRO facility, has ordered a custom-made vacuum furnace tobe utilized in repair solutions for both complex aircraft engines and gas turbines in the energy industry.
Mark Peter Biro Commercial Sales Manager at Aero Space Power Source: LinkedIn
“We decided to acquire in-house heat treatment because we want to be independent in production. It will also give us much better control over the process and treated part quality," commented Mark Peter Biro, commercial sales manager, Aero Space Power. "By installing production capacity in-house and creating our own heat treatment department, we not only become independent from external suppliers, but we also significantly reduce transportation costs.”
The furnace on order from SECO/WARWICK, a company with locations in North America, is unique due to the size of the heating chamber. It has been adapted to the Aero Space Power requirements and has a working area of 51" x 39" x 59" to enable heat treatment of large components up to 55" diameter especially large aircraft parts, as well as gas turbines for the energy sector. The custom technology on order, in addition to non-standard dimensions, is designed to process work in the presence of two gases: argon (used for partial pressure) and nitrogen, which is used mainly in the cooling process. A dew point sensor for each of the gases will be included with the furnace.
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A retort furnace with an Inconel 602CA alloy retort has been shipped from Pennsylvania to a leading manufacturer of motor laminations, located in Midwestern U.S. The laminations are deployed for motors in various aerospace, military, automotive, medical and industrial fields.
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