Here's a relatively new surface-hardening process used by Comp Cams:

http://www.corvetteonline.com/tech-stories/engine/camshaft-technology-what-is-the-nitriding-process/

Parkerizing is a substitute for bluing used primarily in the firearms industry. It's more of a rust preventative process than hardening. I do that on some of the military rifles I rebuild if the owner wants a period-correct finish on something like a M-1 Garand or a 1903-A3 Springfield. All that's required for Parkerizing is the right chemical solution, a stainless steel submersion tank, and a heat source.
Jerry

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