Avoid tempering carbide precipitation

[BluntCut MetalWorks]

I got results inline with my goal, which is to avoid tempering carbide precipitation from AQ to ~375F. However I appreciate alternative views or assessed otherwise - as in lousy ht. It would be great if our discussion mostly focus on tempering & carbide precipitation, and ignoring the rest of ht processs.

4 knives(K0-K3): 1"x3.5" Slicer-Utility 52100(src: Aldo/NJSB) 3/32" thick

Normalized + grain refinement ...
Hardening aust 1480F soak 7 minutes. Evenheat 18KO for hardened-aust & tempered. All knives after quenched, received cold water wash and then LN2 dip.

K2 Quenched->3 seconds*->400F->70F 10 minutes**
HRC: 63.5@AQ 63.5@250F 63.5@275 63.5@300F 63.5@325 63.5@350F 63.5@375 62.5@400F 62@425F
* took 3 seconds to cool from 1480F to ~400F
** took 10 minutes stair step lowering temperature to cool from 400F to ~70F

K0 400F->70F 3 seconds
HRC: 63.5@AQ 63.5@250F 62.5@400F

K1 400F->70F 5 minutes
HRC: 63.5@AQ 63.5@250F 62.5@400F

K3 400F->70F 15 minutes
HRC: 63.5@AQ 63.5@250F 62.5@400F

For my process, if harden aust at 1490F, will produce 65rc AQ. 1500F -> 66rc. But both AQs lead to 62.5rc@400F. Interesting?

Why doing/want this? Once hardened - martensite lattice is formed, tempering carbide formation could(?) weaken the matrix. Also if mart matrix linearly decrease in hardness AQ to 375F, which could mean that martensite lattice is overly stressed and boundary mis-aligned. Further more, cooling time 3seconds or 15 minutes didn't impact the AQ hardness.

I was abled to whittled dry oak with these knives after 250F tempered, 8dps bevel, 0.01" behind edge. Chipped with bamboo. 13dps bevel barely whittle bamboo, ripple edge if start whittle cut with lateral push. 13dps at 62.5rc bamboo fine except a minor lateral dent.