Well, it all boils down to how much retained austenite you have after heat treat. I use CPM154 for all my stainless stuff, so I’m pretty familiar with it. The problem you run into is, the martensite finish temperature (where the austenite has fully converted to martensite) is well below zero Fahrenheit. You “can” heat treat it without cryo and expect a decent hardness, but the retained austenite over time can convert to martensite which is then untempered. Also, the boundary between areas of austenite and martensite is highly unstable, and the combination of the two issues leads to a good chance that the blade can develop cracks down the road. If you want a good example of how much cryo can affect the steel, try heat treating two samples. After they are quenched, stick one in a vise and bend it. As quenched steel should shatter like glass, but I’ll bet you that your sample will bend like mild steel, even if a file still skates off it. Cryo the other, and try the same test. It should break just like you would expect hardened steel to. I know that many high alloy steels have two tempering options, a high temp option that doesn’t use cryo, and a low temp option that does. The high temperature option uses the higher temps to force conversion of austenite, the low temp option uses cryo to force conversion. Usually doing the high temp version is at a small sacrifice to toughness and corrosion resistance. I’ve not used S35V, so I don’t know if that is an option for you. I have not seen that option for CPM154, and have always stuck to the low temp tempers that Crucible recommended. It’s a really great steel, but unless you find a recommended high temp temper option, do not skip cryo, and do it immediately after quench.
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