NITRIDING TECHNICAL CONTENT

The following transcript has been edited for your reading enjoyment.

Advanced Heat Treat Corp.’s Beginnings with Ion Nitriding (01:20)

Doug Glenn: We’re going to be talking about nitriding, specifically, ion nitriding. Gary Sharp has a long history with the technical aspects of ion nitriding.

Tell us a little bit about yourself and Advanced Heat Treat.

Gary Sharp:  I started with John Deere in the Chemistry department. I have a degree in Science Chemistry. Then I went into various other areas: production support and different management positions before I ended up ultimately leaving to start Advanced Heat Treat.

The way I became oriented and introduced to ion nitriding was a company who we had done work with wanted to sell John Deere some new technology. They came in for some meetings, and we had several meetings with top management. But in 1979/80, that was one of the first real downturns in the ag market. So, Deere wasn’t really interested in taking on a new technology at that time. While I was still interested, I talked to various management people. Ultimately, I got permission to invest and investigate, on my own, the ion nitriding process.

Doug Glenn: Even while you were still at Deere?

Gary Sharp:  While I was still at Deere, but I had to do it on my own. All of my vacations, my holidays, and things were spent doing market surveys, talking to various potential users and so forth, in the marketplace, to see if it had a “fit.” Because, obviously, when an equipment supplier comes in, everything is nice and rosy and so forth and the equipment works for everything. That’s not always the case, of course.

After discussion with the management, they gave us permission to continue our investigation. From 1979 to 1981, we did a lot of research. I took vacations and went and did market surveys with different potential customers and found out that ion nitriding still seemed to have a lot of the glitz and the shine from the company that came in to talk to us.

We went ahead and, after a period of time and evaluation, put together an investor base. We put together a building, equipment was purchased, and then we began to do ion nitriding. We started with a 25 KW lab unit and a 160 kW unit that we would transfer from development into production-sized lots.

Doug Glenn:  You say “we,” so this was not Deere though — these were the people outside of Deere — yourself and some others, right?

Gary Sharp:  Yes, myself and several others, at the time. Unfortunately, some things happened and partnerships are not always the easiest. That dissolved, and it was pretty much me and my wife and our employee base. That was the start anyway.

The trouble is, early on, the small lab unit worked fine, and we could do out development; but it didn’t transfer over to the larger production unit. We kept having power supply issues. This went on for months and months and months. Ultimately, I had to get legal involved. That churned around for over a year, probably. Here we’re trying to have a startup business and, at the same time, we’re fighting with everything else. The building came together, the lab we put in worked well, but we just had issues.

We weren’t aware of how many pieces of equipment had been sold in the marketplace by this company until we got into legal, and then we started having more serious discussions. They replaced the power supplies with a new source and solved the arc suppression problems and some of the things that were taking place. Basically, we would get into the range of an unstable arc discharge; and instead of heat treating we were melting the parts. Unfortunately, we couldn’t keep many customers doing that! That got resolved, we got additional equipment in the settlement, and then we took off.

Doug Glenn:  When did you actually start the company?

Gary Sharp:  1981/82 timeframe.

From the market surveys, we knew there was considerable interest. Obviously, we went back to some of those folks and started doing some development work with them, particularly on applications where ion nitriding was a significant advantage over some other treatments. Where I was in Iowa, they were doing gas nitriding on cylinder liners. Again, with the market going south for a while, they weren’t interested in any new technologies; and they just continued to do the gas nitriding.

Doug Glenn:  So, you ran through a little bit of legal issues. When would you say was the first time you felt you were up and running?

Gary Sharp:  I think last week, maybe! It took a while.

In our investigation, we found out they had sold quite a few pieces of equipment; and they’d all been mothballed and put on the shelf. In a way, it was a bad deal, but it was good for us because we had the solutions to fix them.

I went around and purchased equipment, 10 cents on the dollar, and bought additional capacity. We would get up to around 70–80% capacity on one vessel, and then I’d go buy another. I’d get that up and established in our plant. It worked out quite well for us, being dumb and stupid, I guess.

Gary Sharp:  It kind of evolved over time. We’ve got 50+ units now — ion nitriding as well as gas nitriding. The nitriding field has been our baby for many, many years. We’ve done a lot of development with other suppliers to make sure the applications they run are using the right process.

What Is Nitriding? (09:03)

Doug Glenn:  Let’s talk a little bit about nitriding. Then I want to hone in a little bit more into ion nitriding. What is nitriding? How is it different from ion nitriding? What are we doing, and why do we do it?

Gary Sharp:  Nitriding is a case hardening process. It is used on a variety of components to improve wear, abrasion resistance, fatigue strength, etc. It’s generally a lower temperature process (than, say, carburizing or anything like that), so you don’t have the resultant distortion and post machining requirements that you do with some of the existing treatments that are out there.

Nitriding is a case hardening process. It is used on a variety of components to improve wear, abrasion resistance, fatigue strength, etc.

As you mentioned, there is ion nitriding, there is gas nitriding, there is salt bath nitriding. All three do similar things, they just have different requirements. Obviously, there are materials and chemistry that are involved with each of those materials, but you can nitride almost anything, at least putting a compound zone or an outer layer on that’s very abrasion resistant. Where the process gets developed is when you have alloy (Chromalloy, malatium, aluminum); these are nitride formers which, combined with the nitrogen at and below the surface, give you a diffusion zone that has longevity and a very high hardness.

Doug Glenn:  In the simplest terms, nitriding is in one sense hardening the surface of a metal by infusing nitrogen, basically. It’s done in a variety of ways, and that’s what I wanted to ask you a question about.

If the total universe of nitriding is 100%, what percent of that, do you think, is gas nitriding, salt nitriding and ion nitriding? Your best guess.

Gary Sharp:  I’ve heard different numbers. Ion nitriding has grown significantly over the years. Up until that point, gas nitriding and salt bath nitriding were probably 70/80%, I would guess. Ion nitriding is quite visual — it has a purple glow. That’s why I’ve got this purple tie on.

Doug Glenn:  I was going to ask why you have the purple tie on. I wondered why www.ahtcorp.com is purple.

We won’t go into the details of gas nitriding or salt nitriding; that can be a topic for another day. Let’s talk a little bit about how ion nitriding gets the nitrogen into the surface of the metal. How does that happen? How does that differ from, if you will, gas and/or salt?

Ion Nitriding (13:40)

Gary Sharp:  It’s a diffusion process. If you look at a piece of equipment, a hearth plate is a cathode in a DC circuit. The vessel wall is the anode, and the gas is your carrier.

Through the transfer of energy, you bombard the part with ions and neutral atoms. They transfer their kinetic energy, and that is what actually heats up the parts. In the early years, that was the only way you could heat the parts. Later came more developed equipment.

Now, you have auxiliary heating in the walls which adds some advantage, but it also adds a little more complexity in terms of keeping and maintaining a current density on the part adequate to diffuse into the metal itself. Sometimes you put it in a vessel, and you turn on the power supply. All the energy is coming from somewhere else, and you don’t actually diffuse or harden the part itself. It’s been solved, obviously, over the years.

Doug Glenn:  Are you making a positively and negatively charged item?

Gary Sharp:  The ions bombard the surface.

Doug Glenn:  Right. The ions bombard it because they’re attracted magnetically?

Gary Sharp:  Yep. And they transfer the kinetic energy. That’s what heated the workpiece up in the early equipment. Like I said, in later equipment, they had auxiliary heating, as well, in the chambers.

Applications of Ion Nitriding (15:17)

Doug Glenn:  Typically, what are some of the more common applications? Is it mostly agriculture, like John Deere?

Gary Sharp:  By no means. When I was still at Deere and left Deere, we made sure we didn’t have conflict of interest. I didn’t even solicit any Deere parts, and that went on for quite a few years. Since, we’ve done parts for them and so forth.

Anything that has high wear and abrasion. One of the advantages that we haven’t talked about is the ability to selectively harden and the ease of masking. “Ease of masking” means instead of using copper paints or stop-off materials, you can just interrupt the plasma from touching that surface. If you have some threads, you just put a nut on there. It blocks the plasma from touching the threads, and they won’t get hard. It is a physical block. And you have maybe an 8–10 thousandths/8–15 thousandths gap and you still don’t diffuse beyond the masking itself.

There are a lot of ways of masking parts with ion nitriding. Those are generally done on customers’ parts that are repeating, so you don’t have to paint them every time they come in. You let the copper paint dry and all of that. We would just use mechanical masking and just use them over and over. They basically last forever.

Doug Glenn:  I’ve heard one of the other real advantages of ion nitriding is blind holes and areas like that where gas flow wouldn’t necessarily get. Even salt might have a little of bit of difficulty getting in there.

Gary Sharp:  It is an advantage. There is an L/B ratio we must be aware of. You conform that plasma to go down in the hole, if it intersects itself with the other side (it’s called hollow cathoding). That is extremely hot and can melt the parts.

That’s what we learned early on, before we got some of the equipment issues resolved, is that we would get in that unstable arc discharge range. We’d basically melt the work piece. And the customers weren’t happy with that!

Doug Glenn:  It’s a bad day when you open the furnace to a pool of metal. That is not a good day!

We’ve got certain benefits there. Any industry, you’re saying, can do it, anywhere where there’s high resistance. So, automotive parts, yes?

Gary Sharp:  Automotive, aerospace. We did the submarine gear for the Seawolf-class submarine, 35,000 pounds, 160 inch diameter. That ran, probably, 400+ hours. Not because it was big, but because they had an extremely deep case requirement. The diffusion took longer, particularly at the lower temperatures that you run, versus other kinds of treatments.

Doug Glenn: With ion nitriding, you are typically below the temperature where distortion could occur, I believe. So, you shouldn’t have to do post hardening processes.

Gary Sharp:  Yes. That is one of the big advantages, for sure. We found that one of the reasons a lot of our customers transition out of one process into ours was because we eliminated some subsequent operations which they typically had to have and reduced their cost. Even though it wasn’t a direct cost in nitriding, it definitely affected that.

Challenges with Ion Nitriding (

Doug Glenn:  What are some possible challenges with ion nitriding?

Gary Sharp:  Loading a chamber and the part spacing you need, depending on what level of backing they’re going to run at, will determine how wide the plasma is. That, in turn, affects then how close you can put parts together or close to each other so that you still get treatment on both products or both pieces. And it does allow you to do mixed loads of different types of things, depending on the level of vacuum and how wide the plasma that you’re conducting surrounds that part.

This is a concern, and that’s why we review all those. Generally, we even run some test samples for the customer. We let them compare our metallurgy with theirs before they commit even further production loads.

We had a steering torsion bar we probably ran 10,000 pieces in a load. We masked the bottom portion of that because it got cross-drilled in the assembly and, of course, they didn’t want to have to drill through a hardened piece of material. Consequently, it worked out really well for us; and we did that for 15/20 years.

Special Consideration: Parts Cleaning (22:17)

Doug Glenn:  I have heard that when you’re ion nitriding, part cleanliness is a critical part. Can you address that?

Gary Sharp:  Yes. Of course, we clean everything before it goes in the chamber. Typically, it has been either with an alkaline wash or vapor degrease to get rid of any contaminants off the surface. The early part of the cycle, when you turn the DC power supply on, you begin to sputter. So, any oxides and things like that on the surface get sputtered away before you actually ramp up and start the diffusion phase of the cycle.

Cleaning is important. If you have plating, that often blocks out. If you have dirty parts, that will prevent nitriding. Or, an even worse case, it will sputter off and onto other parts and then you contaminate those as well.  Cleaning is an important part of the equation.

Doug Glenn:  Are there any other common misperceptions about ion nitriding that you would like to address?

Gary Sharp:  I don’t know any more. Back then, when we first started, that’s how we learned some of the things we did, of course. The spacing is important, the gaps are important so that you don’t hollow cathode. And, as you touched on a little bit ago, the cleanliness; if it’s really dirty and contaminated, you’re going to have a void in that area and it won’t nitride. Even a fingerprint could cause an issue.

Cleaning parts it’s getting more difficult, right now, with the push to restrict the use of vapor degreasing and things like that. We have to come up with other cleaning methods that are suitable and still meet the end-product requirements.

Wear and abrasion are big benefits. Treating parts at a low enough temperature that you don’t have distortion. You don’t have to set up and post heat treat machine. Those are all key benefits from the process itself.

It’s repeatable. Over and over, we do thousands and thousands of parts and loads at our different locations. It’s been quite successful for us.

Ion Nitriding and FNC (26:07)

Doug Glenn:  Can you put ion nitriding (or nitriding, generally) in perspective with things like ferritic nitrocarburizing, maybe carbonitriding? Where does it fall on the scale? What are the differences between those processes?

Gary Sharp:  Ion nitriding is most effective when you have Chromalloy, malatium, aluminum, and those types of elements in your product. Of course, with carburizing, that’s not a requirement. With carbonitriding, typically, it isn’t a requirement. Both of those processes are done at considerably higher temperatures which then gets you back into the questions: Is the part going to distort, do we have to post heat machine?

Doug Glenn:  I have one last question for you about people who, potentially, could use your services, but I want to dive a little bit deeper into your company before we wrap up. You’ve got three locations, now, correct?

Gary Sharp:  We have four.

Doug Glenn:  Four locations? Where are they?

Gary Sharp:  Three of them do ion nitriding and the nitriding process. Here, in Waterloo, we have the corporate headquarters where we have the largest ion nitriders. As a matter of fact, we are installing one right now that will do parts upwards of about 30 feet. We have Waterloo, Iowa, and we have the two facilities here in essence where we started. It was risky enough, leaving John Deere, without going somewhere else.

Here, in Waterloo, we have the corporate headquarters where we have the largest ion nitriders. As a matter of fact, we are installing one right now that will do parts upwards of about 30 feet.

Then we added Michigan. Dr. Ed Rolinski was our key “go-to” guy up in Michigan. He lived with me for a year and half. Meanwhile, we were building the facility in Michigan; so he could go back to it.

Then we started a plant in Cullman, Alabama. We’ve got the central Midwest pretty well covered with all types of applications. We’re starting to add some other types of treatments: the black oxide treatment® to kind of subsidize the ion nitriding, if you will.

Doug Glenn:  Let me wrap up with this question:  Let’s say there is a company out there, a manufacturer, who currently is doing some sort of a case hardening process. They’re thinking, “I wonder if I should look into nitriding/ion nitriding.” What would be your guidance for them? What questions should they be asking themselves?

Gary Sharp:  Companies have to go through the some of the same steps we did early on —  testing, making sure the parts/the treatment they select is repeatable, and it fits their end-use.

It’s rather expensive equipment. Some equipment is in excess of $600,000–$700,000 apiece. Depending on the size, they can get even more expensive than that.

We do make some of our equipment, now. We have in the past, particularly, when there were things that weren’t available.

If you’re looking to outsource ion nitriding, you’d start first with the material chemistry and see what materials are used. It has to fit the requirements of the end application, as well. That’s probably the biggest thing.

Then, if it’s got alloy in it and you figure out your case steps and your diffusion requirements, next you would do some development testing on parts and see how it worked in the application and go from there.

Doug Glenn:  And it’s probably best just to ask an expert! At least call and check it out.

Is there any part (or maybe there is more than one) that if you have this part, you shouldn’t even consider ion nitriding — it’s just not going to work?

Gary Sharp: In ion nitriding, a key thing to be cautious of — assuming the material is compatible with the nitriding reaction — is wide holes, or holes we can’t conform the plasma tight enough to reach. In those cases, you’d have hollow cathode and then you’d have a melting issue or damage to the parts.

Parts that have to be nitrided all over can also be problematic. Oftentimes, in those cases, you would nitride for half cycles and then flip them because where it’s sitting is actually getting masked, where it’s sitting on the hearth plate or on your fixture plate or something similar. So, those are the kinds of applications that you have to give more thought to.

Doug Glenn:  We appreciate your time, Gary. You folks have been around a long time, and your reputation is one for doing great work. I hope people will get in touch with you.

About the expert: Gary Sharp founded Advanced Heat Treat Corp., “AHT” for short, in 1981. The company initially went to market with its UltraGlow® ion nitriding & ion nitrocarburizing services, but since then, has expanded its offerings to also include gas nitriding, gas nitrocarburizing and UltraOx® as well as more traditional heat treatments such as carburizing, induction hardening, carbonitriding, through hardening and more.

For more information: Contact with Gary or learn more about Advanced Heat Treat Corp. at www.ahtcorp.com, or call 319-232-5221.

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