Most basic blade hardening steps

[me2]

So, if we then reheat this blade during sharpening, does it further soften the steel or work harden the edge like heat treating it?

If the blade is reheated to a higher temperature than the original tempering temperature, then softening can occur. The heating of the edge does not work harden the blade. Work hardening requires the material to be permanently deformed (plastic deformation) via cold rolling, peening, cold forging, bending, or any number of other means. Technically, machining and grinding create a very thin layer of work hardened material just under the material that was removed. However, this is generally not considered in cutting tools, as the ductility of the material is generally very low in hardened steels, and some ductility, or ability to be plastically deformed, is required for work hardening.

This video shows machining in slow motion and you can see the cold worked layer just under the cut. It's very thin, even here. This is for machine cutting bits, but similar layers appear under ground surfaces. Also, note how ductile the material is and how little the hardened bit moves. No deformation, either plastic or elastic, is visible to me.

https://www.youtube.com/watch?v=2fDJ1Wk-y04