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In addition.
I'm looking at tempering data for 440c and it requires a low temperature quench, 300 without the cryo would seem to leave you in the Rc-57 range and cryo would add about 1 point maybe. I made a few knives with 440c, but not many and they were around 58 with a double temper at 300 degrees if my memory serves me right, but they were tempered only for 1 hour each with dry ice in-between and contrary to some HT opinion dry ice does make the steel tougher. Two hours btw is all you really need for LN from what I gather from my HT. Doesn't hurt or help to leave it in longer, leastways that's all my HT guy does and I have no complaints on the quality I get in return.
440c is a high carbon, high chromium steel with less than one per cent of Moly and no Vanadium so no V carbides, but there is more than enough Chromium carbide formation though. The moly just adds some toughness along with the manganese as they prevent grain growth. Moly also forms carbides and helps with the chrome too. Far as I can tell all air quench steels have moly in them and all knife steels have manganese.
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