Oil hardening? and "Tool & Die shop" question

I don't remember exactly what case hardening is, (I forgot) but I think
it's a chemical hardening method.

It does something to the outside surface, a very thin layer of the
metal.


I'll guess that if oil hardening involves quenching from a higher
temperature, as with water, it has something to do with the rate of
change of the cooling process and the alignment of the metallic cystal
structures.

Heat treating within the realm of metallurgy is interesting (I think so
anyway), especially pondering how they figured this stuff out...probably
dates back to accidental discoveries...Bronze Age, Iron Age, etc.

With some materials the duration at a particular temperature is
important too, so back to my guess, oil cooling probably allows a dwell
at a higher temperature and a slower cooldown thru that higher
temperature range...water can't go over 212F/100C unless the steam is
pressurized.


Back to an earlier question I posted with no responses, I was advised to
just talk to a local tool & die shop for some prototype parts I
need...hopefully they'll just tell me if they're not interested and
price me out of possibility if not interested.

Murray