Hardenable stainless for mildly cold application?
Hardenable stainless for mildly cold application?
(OP)
We are a commercial heat treater working with a potential customer on carburizing a stainless steel. The idea is to replace 4-5" diameter pipes currently made of carburized 8620 material. The pipes are failing after 3-10 weeks. They think the failure is due to corrosion, thus the move to stainless steel. The pipes have integrated bearing races that need to have high 50s Rockwell C hardness, thus the carburizing at least of the race areas (potentially the non-race areas could be masked if the carburizing lowers the corrosion resistance too much.) The core uncarburized areas have the following mechanical requirements:
A. Minimum Tensile Strength = 119,000 psi
B. Minimum Yield Strength = 95,000 psi
C. Minimum Elongation = 15%
D. Minimum Reduction of Area = 35%
And there is a requirement for a Charpy test at -20°F to have three samples all above 15 ft-lb with the average of the three at least 20 ft-lb.
They have initially come up with X4CrNiMo 16-5-1 and 431 as candidate materials. They provided 16-5-1 samples to us to use in developing a low pressure (vacuum) carburizing process. In addition, they requested that we suggest alternate materials (so they can compare price and availability, I think). Any suggestions for me to look into that I could pass on to our customer would be greatly appreciated; it would be a special bonus if any of the materials have carburizing process data available.
A. Minimum Tensile Strength = 119,000 psi
B. Minimum Yield Strength = 95,000 psi
C. Minimum Elongation = 15%
D. Minimum Reduction of Area = 35%
And there is a requirement for a Charpy test at -20°F to have three samples all above 15 ft-lb with the average of the three at least 20 ft-lb.
They have initially come up with X4CrNiMo 16-5-1 and 431 as candidate materials. They provided 16-5-1 samples to us to use in developing a low pressure (vacuum) carburizing process. In addition, they requested that we suggest alternate materials (so they can compare price and availability, I think). Any suggestions for me to look into that I could pass on to our customer would be greatly appreciated; it would be a special bonus if any of the materials have carburizing process data available.





RE: Hardenable stainless for mildly cold application?
Is carburizing required because of specific case depth and hardness requirements for service conditions? What rides against the races? What are the operating conditions? I can go on but as I mentioned, much more background information is required to evaluate suitable materials.
RE: Hardenable stainless for mildly cold application?
The first thing that comes to mind is 13-8PH. Good corrosion resistance and high strength.
You might look into SolNit-M or S3P or StaniHard for the surface treatment.
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P.E. Metallurgy, Plymouth Tube
RE: Hardenable stainless for mildly cold application?
They had some parts nitrided (by another source, the company I'm at doesn't have nitriding equipment) and decided against nitriding. Again, it's been hard to get details out of them on why they decided not to nitride.
I understand about not having enough information - I appreciate you guys reviewing my post and commenting, it helps. Thank you also for the pointer to the stainless hardening processes, those are interesting to read about.
RE: Hardenable stainless for mildly cold application?
RE: Hardenable stainless for mildly cold application?
They are process to diffuse N into the alloy without forming any nitrides.
They harden the surface without reducing corrosion resistance.
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P.E. Metallurgy, Plymouth Tube
RE: Hardenable stainless for mildly cold application?
Ion/plasma nitriding,Kolsterizing are special treatment and cost benefit analysis will have to be performed .
Ed's choice of 13-8PH is a good one.
"Even,if you are a minority of one, truth is the truth."
Mahatma Gandhi.
RE: Hardenable stainless for mildly cold application?
If surface corrosion is your concern, then I would recommend using a carburizing steel like 8620 or 9310 for the races, and coating them with thin dense chrome for corrosion protection. It is common practice with commercial bearings to apply thin dense chrome over E52100 steel races for corrosion protection rather than using more costly corrosion resistant alloys like 440C. Rough machine the pipe and race surfaces, carburize/heat treat them, perform an intermediate grinding operation on the race/journal surfaces, apply the thin dense chrome plating, and then perform a finish grind operation on the race/journal surfaces.
RE: Hardenable stainless for mildly cold application?
RE: Hardenable stainless for mildly cold application?
Unfortunately in this case our customer's interests and my company's interests diverge, because their other options would lead them to not give us any work. At this point we're focused on heat treating their chosen material as best as possible and just keeping in mind that they later might find an alternative path and pull the work from us.
I really appreciate all the comments here - I have learned a lot from them (always a good thing in itself) and they have helped me extract some additional background information from our customer.