Wikipedia calls it
cryogenic hardening. I had a set of brake rotors and drums sent to Cool Rotors in Michigan. It about doubled the cost of the parts, but may give 3-4 times the service life. So far the rotors are unscored.
I found the Isotropic Superfinishing in an article in HotVWs. A transaxle rebuilder in CA will do a whole Vanagon gearset for $250, so less than that.
Magnafluxing, of course, has been around since the '40s.