52100 heat treat summary.

Like Samuraistuart said, with all that time at temperature it is necessary to be sure to get rid of any residual decarb layer that could have your reading lower than the steel underneat. 52100 i think should harden very well even in not pre heated oil....:confused:
Anyway if it would have been decarb i believe it would have showed in polishing since it's appearence would be duller than the silvery steel you got (me too find 52100 particulary brilliant).

I can make one guess...may be a shot in the dark
If i were you i would have thought my TC were reading a bit higher, assuming i were hence soaking below 1475°F. That would have lead to first time quench lower hrc; but the second time the martensite "stored" the carbon bringing readily into solution and the second soak added a little bit more carbon, giving me higher hrc.
This could be veryfied testing the same procedure but quenching from 1485 °F (assuming: closer to "real" 1475°F), and see if the hrc goes up...

If, on the contrary your TC were reading lower than reality i assume things would have been worst in the second quench due to more RA.
 
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Stezann I have to admit that I was too wondering about the readout on my oven. I guess there in no real way to tell except do another batch and up the temp 25 or so degrees. I did sharpen up one of the test blades and it is noticabely sharper than same blade in 1084 in same geometry. I also quckly wittled a little wedge out of seasoned oak and it still shaved in the same manner it did before. The grind is chisel with 25 secondary. This steel is honestly all it is worked up to be. I am soo happy with the results.
 
Here is a pic of a 2 3/4 scandi blade that was one of the test blades. If you look closely you can see the indentations from HRC probe. I wanted them to measure more foward on the blade where I know that all de carb has been removed but hey, you should not look in gifted horses mouth. They dont charge me to test.

As you can see I leave the tang oversize so its easier to hold while grinding. That makes for a instant cupon that I then broke in three pieces to check for grain size. Photos were taken with I pad and it actually looks finer than in photo. Definitely finer than a 1084 I broke few monts ago in the same manner.

One thing that I did notice 52100 will acctually bend and not return true while I was trying to break it. I might add that I had to use large pliers do do so. Pretty tough little piece. 1084 I broke would flex roughly 35-40 degrees and would still be straight as an arrow.

Let me know what you think.




 
The grain seems fine, the bending often means RA or insufficient saturation with carbon in solution...i would exclude pearlite leftovers for 52100.
So far it seems you are doing fine, if you get the chance maybe you could try checking the temps the way we hypotized.
 
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