Heat treated 52100 thinking it was AEBL

JTknives

JTknives

Blade Heat Treating www.jarodtodd.com
Joined
Jun 11, 2006
Messages
8,647
So yeah I figured I would make a quick post about this. A customer sent me blades and we processed them as thy where marked. Well after discovering something was off we contacted him asking if on of the aebl blades was not aebl. He looked into it and the blade ended up being 52100. I will let you guys guess what clued us in that the steel was not aebl and what the results where from this heat treat.
 
Substantially different looking scale/decarb pattern. Some what lower hardness, although coarse grained trash can still test hard. Super big grain, and brittle.
 
I guess you have guessed enough.
It came out perfectly straight and after a 300° it reared its head. 62.5-63 is common with our 300° temper but this blade was 66rc. I then reached out to the customer and found out it was miss marked. So I’m guessing the blade was one single grain after being soaked at that temp for 20min. But it was just plate quenched and still hit 66. I planned on re-cycling it through the oven and give it a proper heat treat but the customer wanted it to see how it worked out. So I’m waiting to hear back on how it preformed. I’m planning on doing some tests because I so wanted to snap that blade and look at the grain under the microscope.
 
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This caused me to go back and re read Larrin's post about heat treating 52100. There was a graph of aus temp and resulting hardness that showed that as aus temp increased so did the resulting hardness. The highest temp he used was 1650 so who knows for sure but it does make some sense that you got the result you did. His results also showed that toughness tanked as aus temp increased over 1600.
My guess is that that blade is going to be extremely brittle and chippy. It's too bad he didn't have you do a DET anneal and re harden.

https://knifesteelnerds.com/2019/05/13/how-to-heat-treat-52100/
 
I’m guessing he was as curious as I was and wanted to just play with it. He had other blades in the blanch that came out perfect.
 
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