Had to share - VERY hard steel

K

Knifemaker.ca

Dealer - Purveyor
I referenced this in another thread, but thought it deserved it's own mention. A customer recently sent me a blade ground from CPM Rex121 for HT. Strange stuff but it heat treated without problems. 2200F with 15 minute soak - RHC63 off the quench plates - RHC68 out of cryo - RHC 70 out of first temper (1025F) and just a tiny bit more in the end after three tempers.

It may well be we've finally defined "harder than a woodpeckers lips". :biggrin:

Curious to hear how it performs. It isn't stainless - and it surely won't make a prybar. It will likely be hard to sharpen, but's also possible it will never need sharpeneing. :les:

Rob!
 
Sounds like funny stuff, hot temps for non stainless. It would be interesting to see how it preforms.
 
That steel has some wicked specifications to it. The Charpy Notch spec on it is about 11ft lbs to the same manufacturers 440C at 16. I don't know what HRC the test is typically calibrated at or any other variables so getting an apples to apples comparison is going to be tough. The advertised wear resistance is off the hook...I'd like to have some first hand results and possibly a destructive test. Niagara Specialty Metals is supposedly a possible vendor.
 
No, it's not possible that it will never need sharpening if it is used long enough. There are some things, like cardboard boxes and fibrous rope that will take the edge off of even these wonder steels. Personally, for what it's worth, I think that there's a definite down side to steels that are so wear resistant that they are hard to sharpen.

Doug
 
Best guess is that it's a complex enough steel that it has a secondary hardening node, generally found around 1000°, where native carbides are formed. Note that it was tempered at 1025°. The increase with the cryo was probably due to forcing the retained austinite to convert to untempered martensite.

Doug
 
Yeah, I've heard of steels doing that and how cryo'ing can gain hardness points, but I have never seen that dramatic of an increase! Pretty neat!
 
Sorry Mooseyard. I didn't hink to take and pictures because a blade on a rockwell tester isn't all that interesting. It's on the way back to the maker now.
 
Taz575. If you look at the data sheet for Crucible's 154CM in the 2000F column, the difference with cryo is something like 9 points as quenched. You're right though. 1 - 2 points is more typical.
 
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