To add to Bob's comment, something to keep in mind with case (or pack) hardening and through hardening is that the depth of the case, the skin, is dependent upon how long the part is kept at or above the correct temperature. If something like a little cam is held only for a few seconds before quenching, the case thickness won't be more than a couple thousandths, and once that wears away, soft steel is exposed and the wear will accelerate.
So a one-lobed cam for a small IC engine that is maybe 0.500" OD would be best kept at temperature for 5 to 10 minutes, and this can be tricky. Too high and the steel can be harmed.
Also, the Kasenit or other compound melts and forms a protective shell, but any areas subject to dull red heat without the molten salts can oxidize badly - you get black scale, iron oxide, that can be up to .005" to 0.010" thick; it'll flake off and ruin fine dimensions if care is not taken. It looks bad, too. So gob that stuff on there as the part heats up, and add more during the process. The part will look like a badly crisped BBQ item, with a thick shell so that you can't even see the shape of the part very much anymore!
For O-1, W-1 and the like, a borosilicate glass like KeepBryte saves the day from scale. All that said, my favorite higher carbon steels for small parts these days is A-2, an air-hardening steel. You can wrap these up in stainless steel foil during heat treatment, and there is no liquid quench, no scale, no spatter, no fuss. The parts come out greay to purple, attractive, and squeaky-hard.