CPM M4

CPM M4 has a moderate carbide volume (13.5%) that is roughly half softer high-speed steel carbides (similar hardness to chromium carbides) and half harder MC-type vanadium carbides. While CPM M4 can be sharpened on conventional stones it benefits significantly from diamond or CBN abrasives.

CPM M4 was originally developed for metal cutting applications. It is known for its good balance of toughness and wear resistance. I consider CPM M4 the middle of the spectrum of the high alloy steels. It is well suited for all-around workhorse knives for those with access to diamond abrasives to sharpen it. I harden my CPM M4 to between 62 and 66 Rc depending on the desired characteristics and it exhibits a fairly wide range of properties over that range.