Case harden 316l?

Wouldn't it form carbides everywhere, especially on the grain boundaries, particularly with Chromium, serving zero useful purpose and thereby "robbing" the metal matrix of the solute metals which make it stainless? ie. you'd get a brittle material which corrodes badly?

There's extremely high-carbon stainlesses made by powder metallurgy, giving a pocket knife costing about US$100 and where you can both do any normal task and shave with it.

I don't know whether a carbon-rich layer would work, but if not maybe nitrogen or something?

I am looking for an easy(-ish) home workshop process if possible.

Peter F

coat with stellite and regrind?

Useful properties are obtained by giving a high-carbon layer to stainless steels. This was being looked at 20 years ago as I met it. They were aiming for around 6.5%C. Can't remember the method used. Cannot be "case-hardening" with time at temperature in a carbon-source material, as the carbon would react with the alloying elements and give carbides (?)