How can carbon harden 316L & improve corrosion resistance? 7

[rnd2]

In thread 330-49696 TVP mentions a surface hardening process called Kolsterising.
Apparently tough corrosion resistant material like 316L can surface harden to 75 HRC with Kolsterising.
Apparently corrosion resistance is improved, particularly if molybdenum is present; the hardening agent is carbon which is infused into the metal surface and the infusion process ensures carbon does not react with chromium to form chrome carbides.

1) Can anyone list the conditions where this process improves the corrosion resistance of 316L?

2) Can anyone list the conditions(if any)where this process inhibits the corrosion resistance of 316L?

 

[rnd2]

Thank you for your interest unclesyd.
Spotting, and its ramifications has the potential to translate into a BIG problem for our application.
I have very quickly read James R. Easterday, P.E. paper about Kolene process. It seems the process is intended for regular steel rather than stainless yet I notice you used it with 17/4 sleeves. Could it be used to coat a heat hardened Martensitic stainless? What happens if some of the coating is penetrated?
I would like to continue to use 316L but desire to modify either it or its surface to >58 HRC at the same time maintain its existing excellent corrosion resistance against seawater .
The Kolsterising process showed promise, until the air induced brown surface specks emerged. They seem unpreventable because the pacification treatment suggested in an earlier post seems very iffy to me. Actually come to think of it, the cast parts were passivated before delivery and before kolsterising treatment and they showed the same brown specks as the machined parts, but not as many.
If 316L is not a viable option then I would very much appreciate suggestions that may be.

 

[unclesyd]

Here are two leads for additional processes for hardening Austenitic SS. I haven’t checked them out but have recommended the first system for some extrusion machine components.

http://www.industrialheating.com/CD...ures/BNP__Features__Item/0,2832,99594,00.html

This is a new one and may be linked to Japanese process.

http://www.asminternational.org/Con...wsArticle.htm?SMContentIndex=5&SMContentSet=0

 

[rnd2]

Thank you unclesyd. These leads appear most helpful and I will follow them through.
Regards
rnd2

 

[rnd2]

I would like to thank everybody for their contributions.