AJ300MAG:
But would the Cyro treating also stress relieve? It is my understanding that the purpose of Cyro treating was never intended to stress relieve.
It is also my understanding that the purpose of cyro treating is exactly what you describe, to change the retained austinite to martinsite.
Also, the parts were stronger, stayed sharp longer, and were more dimensionally stable after cyro treating.
If I understand you correctly, you are saying that the cold would change the dimensions of the part, causing problems, unless the cyro was done immediately following austinizing.
If this is true, a barrel cyro treated later could very well change dimensions, causing more problems that it fixed.
My only experience in cyro treating is sending knifeblades made from 154 CM to a professional heat treatet.
The blades are stress relieved at 1200 degrees F, then taken to austinizing temperature. Then cooled to room temperature and cyro treated before tempering. The stress relieving is done before the knives are even heated to the heat treat temperature.
This person is a professional heat treater, who heat treats the blades of most of the knifemakers nation wide, including many factory blades, and I would trust what he tells me over what I read in Wiki.
Although I was not aware that the martinsite conversion continued after heat treating as you explain in your post, where the parts were put into service in cold temperatures. I thought it happened within a few seconds to a few hours after austinizing.
