Industrial Heating is fortunate enough to have several experts in their respective fields contribute editorial pieces on a regular basis. These experts – David Pye, Debbie Aliya, Dan Kay and Reed Miller – all have a vast amount of experience in the thermal-processing industry. As such, their blogs and columns provide helpful and timely information about heat treatment to our readership.
Since our editorial focus in April is consulting, we asked a couple of our experts involved in that side of the business for their insights … and for some of their most interesting stories. With that in mind, here is what metallurgical consultant David Pye and failure analyst Debbie Aliya had to offer.
Pye is the owner and operator of Pye Metallurgical International Consulting. He has nearly five decades of practical experience in captive and commercial heat treatment, metallurgical laboratory operation and industrial furnace sales. Aliya is the owner and president of Aliya Analytical Inc. She specializes in failure analysis and is publishing a book on the subject. Both have been contributing articles, blogs and columns regularly for many years.
style="margin-bottom: 0.0001pt; color: black; text-align: center;"> According to David Pye, safety in the workplace regarding heat treatment connects each and every person who works in either a captive or a commercial shop. // All graphics provided by the authors, except where noted.
David Pye: Metallurgical Consulting
The information that follows is based on my extensive consulting career. I will be sharing a few memorable cases that will hopefully be useful and enlightening. In the consulting business, unusual cases crop up periodically. Case 3 is a prime example.
Pye Metallurgical Consulting began shortly after I departed from a well-known furnace manufacturer based in the United States. PyeMet started out in a consulting capacity and soon included an educational aspect. Later, upon relocating to the United Kingdom, PyeMet was renamed Pye Metallurgical International Consulting. Currently, it is located in Newport News, Va.
During approximately 47 years of metallurgical consulting, I was surprised to learn that many problems are not complex at all but rather simple. Believe it or not, the failure of a component, product and/or equipment can stem from lack of maintenance and cleaning. When cleaning and/or maintenance is not the main cause, there are more serious matters to take into consideration, which brings me to my first case in point.
Case 1: Gaseous Nitriding and Control of Gas Analysis
I received a telephone call from the United Kingdom with a serious atmosphere control problem on gaseous carburizing. The client had very little control and understanding of the gaseous chemistry reaction. For example, methane and propane each have the presence of carbon to produce a martensitic metallurgical result. The problem was in the component and was identified as a lack of case uniformity.
I advised the client to obtain knowledge and understanding of how carbon is necessary to produce a case based on component analysis. The differences in carbon-content percentages and variations with the analysis of each of the process gases to which they were using was also pointed out and explained. This issue was resolved by analyzing the gas based on experimental procedure.
style="margin-bottom: 0.0001pt; color: black; text-align: center;"> One of the many jobs of a heat-treat consultant is to perform microhardness testing on parts. // All graphics provided by the authors, except where noted.
style="margin-bottom: 0.0001pt; color: black; text-align: center;"> David Pye might be called to consult on how an industrial furnace is operating. // All graphics provided by the authors, except where noted.
Case 2: Understanding the Nitriding Process
This case was located in a Pacific Rim country and was identified by the client as a “steel problem” due to variations of measured hardness results. The history of the problem was consistent. Variations of hardness on the product was observed and noted. It was then concluded that it was not a problem with the steel analysis but with the preparation of the product prior to the nitriding process.
The product was not pre-cleaned in an appropriate manner for the satisfactory diffusion of nitrogen into the product’s surface. When the appropriate pre-cleaning was applied, the problem disappeared.
It was then decided to conduct theoretical heat-treatment principles regarding the necessity of preparing good pre-cleaning of the components for nitriding. The downside of the stainless steel groups is that there is a strong likelihood that the stainless steel will lose its resistance to corrosion. This is generally caused by the formation of chromium nitrides in the surface compound zone.
Ultimately, the problem was due to the client’s lack of understanding and knowledge of the nitriding process by either gaseous methods or by pulsed-plasma nitriding. They also did not adhere to the standard operating instructions on the process of nitriding.
style="margin-bottom: 0.0001pt; color: black; text-align: center;"> A metallurgical consultant can be asked to do many things to help a company solve a problem. // skynesher/E+ via Getty Images
Case 3: Heat Treatment of Metals
This case was located in one of the Central Arabian countries. The goal was to instruct company staff on the heat treatment of metals because there was a great deal of confusion understanding the principles of the heat-treatment process, particularly gas nitriding. The other problem involved the finished products being rejected by the client’s customer.
There were two different groups within the company: the manufacturing group possessed limited instrumentation and consistent services; the inspection group who oversaw the end result lacked knowledge of what the heat-treatment process entailed. The history of the problem was consistent within both groups when it came to accomplishing a consistent, repeatable result and a satisfactory processed result.
Furthermore, the engineering staff possessed the microscopy equipment for examination, whereas the heat-treatment staff did not possess any metallurgical inspection equipment outside of hardness testers and an etching station for visual examination. There was a conflict as to who was in prime control of the final metallurgical inspection of the product to ensure that the company could produce a satisfactory product.
Management requested PyeMet to assist in determining the most effective method of surface treatment – nitriding or carburizing – to produce an accurate and repeatable method for all diffusion processes required by the end user. PyeMet eventually concluded that a gas-assisted procedure or a plasma-assisted procedure could be utilized to control the steel surface metallurgy in terms of cost effectiveness and to produce clean, finished components with the appropriate final surface conditions.
There was also a strong emphasis on the requirement of process temperature accuracy. PyeMet determined that the process temperature was only required if utilizing plasma-assisted process technology. Therefore, the component would always display the product process temperature, which would always be measured and controlled from the product setpoint temperature of the furnace.
Because the procedure is “low temperature” for the diffusion of the process gases, the potential for growth of the component is always reduced. This includes shape or size distortion. Masking to create soft areas is a simple procedure that follows the premise, “What the plasma glow sees, it will nitride.” So, the stop-off method can simply be a piece of thin sheet steel that will effectively protect the area that needs to be kept soft.
Case 4: Nitriding an Internal Bore
PyeMet was hired a few years ago by a client based in the United States that was experiencing difficulties with the process of nitriding in a deep, straight-through hole. The case in the bore was collapsing, flaking and not producing a uniform nitride inner bore surface.
Microscopic examination proved to be strenuous due to the low magnification being unable to reach into the depth of the bore.
In order to ensure that nitriding was occurring uniformly in the hole, a process-gas delivery method was created. A long tube with perforations in the wall of the inner tube was inserted into the hole. The result? A number of sputter remedies was completed, and the inner bore was producing acceptable results.
Debbie Aliya: What does a materials engineer specializing in failure analysis do?
Life is always interesting when people bring you their component engineering problems. As a materials engineer, my focus is always on what happened to the physical component. I wish more people would ask me about the cultural aspects of how they do business that promoted the failures. Our capitalist system, and any other imaginable economic system, exists to facilitate exchange of goods and services, not to promote thoughtfulness. But failures at least provide an opening for people to ask questions beyond the basic, “Who do I blame?”
One way to look at the next level of failure analysis is to try to understand if the company’s business model includes a comprehensive engineering design process or whether it’s better described as a company that operates on tribal knowledge. Even though many companies are using advanced modeling techniques, that doesn’t mean that all such companies take advantage of the latest engineering developments at every step of the design process. I always try to get a sense of how my client operates so that I can propose an appropriate level of service for their current issue.
One of the keys to a successful project includes providing a detailed description of how the problem arose and, if desired, how to avoid recurrences. Who did the company send to the failure-analysis service to start the inquiry? Was it the engineering manager, the engineer responsible for the end product, a quality engineer, the owner or a summer intern?
What I really wrestle with as a failure-analysis consultant is communicating the fact that ensuring good, useful data requires background data. Background data includes more than the engineering print and the latest material and process certification documents. Background data includes helping the consultant understand the design, engineering, quality, manufacturing, marketing and service environments. Those are often much more challenging than figuring out whether it bent, broke, wore out or was damaged by impinging environmental factors. Educating the client about the range of concerns that need to be addressed if a useful failure analysis is to be performed is an ongoing challenge.
If you are curious about the physical, mental or cultural aspects of failure analysis, please reach out to request copies of relevant chapters of my forthcoming book, Constructing Competence in Failure Analysis: A Technical and Philosophical Guide.
style="margin-bottom: 0.0001pt; color: black; text-align: center;"> This image shows a deep cup-shaped part sent to Debbie Aliya. The lower black rectangle shows the crack initiation. The rainbow, orange, red and green arrows show the beach marks at later and later stages of crack growth. The green rectangle (left) shows some faint beach marks that are mostly radial in orientation. The crack, once it broke through the wall at the bottom, made its way around the circumference. We also see quite a few ratchet marks along the inside diameter of the “cup” to the left and especially to the right of the central-initiation black rectangle. // All graphics provided by the authors, except where noted.
As can be clearly seen, being a consultant is an important job in the thermal-processing industry. That is why Industrial Heating is fortunate to have several of these experts provide valuable editorial content for our readership on a regular basis. You can keep up with David Pye and Debbie Aliya via their blogs, and you can also read their quarterly Technical Talk columns. Our other bloggers, including Kay and Miller, can be found here. Take advantage of the educational information that can be easily found on our website.
All graphics provided by the authors, except where noted.