304 + O2 (K720). Core is soft

[PEU]

Im doing experiments, this one I tought it would work better, but not, its a 304 stainless+O2 core sanmai. After the whole hardening/tempering process based on Bohler K720 datasheet, a steel I know and use a lot, the core is soft, around 40-45RC on my hardness tester.

Can you guys tell me what went wrong? can the carbon migration be that high that it depleted the O2 steel of it carbon thus reducing hardness significantly? or its something else?

Here are some photos, red lines mark the diamond indentations:

I want to learn something out of this. Thanks!


Pablo

 

[kuraki]

Did you grind it back that far before heat treating? Or wasn't the O2 exposed when you quenched?

 

[JTknives]

Was the O2 exposed to the quench oil, did you have the edge bevels ground befor heat treating. If not then the core could have cooled slow enough to not get a proper quench?

 

[PEU]

It was quenched without grinding, K720 is very forgiving regarding quench speed, the datasheet allows 10 seconds to pass the pearlite nose, Im pretty sure in less than that even with the cladding it would harden properly.
Since in its current state is more a spatula than a knife I will grind a little of the edge to leave it thicker and re harden, now that the core is exposed if there was no migration all should be dandy...


Pablo

 

[kuraki]

Well that's the other possibility, you're so shallow into revealing the core you may be testing a layer with significant migration?

The times I've done this with 1095 and 1084 they came out hard no problem.