Too hard- - - - -drill rod and other high carbon steel alloys can be annealed and tempered to any stage of hardness/toughness needed for different applications by some judicious application of heat and/or quenching in various cooling media- - - -air, oil, water, or even sand. Stellite makes great exhaust valve seats for engines running on "dry" fuels like Natural Gas or LP, but it's far too brittle for most other applications. I have made some very long-lasting lawn mower blades by building up a layer of hard-facing welding rod on the cutting edges, though!
Jerry
