Totally unrelated to gears, but I've been doing a lot more blacksmithing for ornamental iron projects and a few knife blades. To harden the knife blades, I throw them into the forge until they are a uniform dull orange then quench them in used motor oil. After doing this 3 or 4 times, I then sharpen the blade. They seem to hold the edge pretty well as opposed to a raw piece of flat strap (I used to cut out knife blades on my band saw when I was 9 years old. They would bend over & go dull in a day from normal use).
Just wondering if this process could be done to gears?