It turns out that my memory wasn't playing tricks on me:.
One interesting thing - they quench in olive oil.
It also turns out that various kinds of liquid soap or detergent also work:.
Kasenite is also used: heat the metal up, roll in the powder, heat to red heat, quench.
If you don't have Kasenite, in a pinch, use sugar: .
The above methods yield a fairly thin case, and repeated application is used to deepen the case.
Probably, any substance that yields a tightly adherent char will work. I suppose one could as well varnish the item before heat treatment begins. Or barbeque sauce. The process appears to be millennia old.
One can also use the above process and materials to prevent decarburization, which was my original purpose. Decarburization is the opposite of case hardening.
Now, all these examples so for have the metal at a red heat, maximum. Well, some go to orange-red. We'll see if this works at a orange-white heat.