Has anyone heat treated hotroll steel/Do we have the materials to do it? (Some sort of carbon additive?)
I don’t know, but doubt that you will find the commercial stuff at the space. It was moderately expensive and isn’t a common use item (and if I remeber correctly contained some HIGHLY toxic compounds).
You have a couple of options.
This is the commercial stuff:
Cherry Red Case Hardening compound
or I remember reading a article in one of the Machinist Bedside Readers about sealing the part in a tea tin with some bone meal a some chemicals (a cyanide compound was involved I believe) and ‘cooking’ it in a campfire to carborize the skin of the part.
A search on ‘Case Hardening’ may turn up more information. I have never done it myself.