Originally Posted by
David Bassett
I suspect you aren't distinguishing the general "hardness", e.g. HRc 62 (or whatever), or the iron/blade with much harder carbide particles in the high alloy steels which help it hold* an edge and make it harder to sharpen. Lots of threads discuss which abrasives cut which carbides present in which steel. Plain steels, carbon & iron, can be heat treated and tempered to remain very hard, e.g. Japanese blades in White #1 at HRc 65+, and still be relatively easy to sharpen.
(* Warren may drop back in to point out it is an inferior edge that is lasting longer. Depending on what you're doing this may or may not be important. E.g. carbide router bits seem an advantage in MDF, but much less so for delicate hand carvings.)