STAINLESS HEAT TREAT UPDATE. DESTRUCTIVE TESTING

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Heat treatment Nr 1
A complete failure in my book.
I austenitized at 1065 Centigrade,and overnight in dry ice and isopropanol.
I could not temper the blades below 61.5 Hrc without going into the sensitisation range. The blades were very chippy however tempering into the sensitisation range improved things vastly
Heat treat Nr 2
Austenitized at 1045 Centigrade, No freeze cycle as I had ran out of dry ice, but did chill the blade to minus 20c to extend conversion range slightly.
Double tempers one at 250C but was too hard. Second temper at 315C ( each at 2 hours) for 58.8 Hrc. MUCH improved performance and flew the brass rod test. Cardboard cut testing was impressive and took place before I filmed the rest of the clips, I also did not sharpen the blade after cutting cardboard as it was still hanging on a finger nail afterwards!
Tested to destruction, I was impressed by how the edge held up considering it was a lean scandi and also how it flexed and returned but feel there may be improvements still to be had.
The blade did fail to very small chips together with some rolling. The chips were tiny and very symmetrical which is a good sign. Grain structure must be fine.
Heat treat Nr3 and Nr4 will follow with dry ice and LN2. I may even lower the Austenitization temps a bit as it's possible the kiln thermocouple could be reading lower than actual reality (this is not unusual, all thermocouples can drift with age and even new ones can be off)
Not quite ready to let the Stainless knives out just yet. I would like to spend a little more time experimenting to see if I can improve things further.
I was however very impressed by the second heat treat even though I had no more dry ice to do a proper freeze quench..
Hopefully will have something I am happy with shortly.
Thanks
Sandy

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