I am looking for treatments to harden steel (AISI304 in my case). Luckily, I have found a promising method called borinox and boronizing, which my steel grade qualifies for. But then I had a look at their list of possible steel grades to harden: Materials | Hardening of Stainless Steel and I'm pretty sure that this can't be all of them.
I recall reading somewhere that mild steel isn't well fit for case hardening and heat treatment. Why is that? Does that have something to do with is elemental composition or its elemental structure? Does it depend on the alloying elements? What about *just* carbon steel? Can that be heat treated?