Some interesting results from yesterday. The no cryo/low temper z-wear came out at Rc55. I used a lower austenitizing temp, of 1925 to try to minimize or at least lessen the retained austenitite. Tempering was at 400f x 4. According to the data sheet, it should have been Rc58/59 with high temper. I’ve done a few knives for harder use at 1935f, with cryo plus low temper, and they come out at Rc62/63. I had another maker use his tester, and he got an average of Rc62.5 on the blade I sent him. It appears no cryo with low temper isn’t a viable heat treat. The sample can go to be tested anyway.
The cryo (1h, as the eta carbides get erased when using high tempers anyway) plus high temper came out at Rc62, but I didn’t grind the small amount of decarb off. I used 1925f as an educated guess as earlier testing using 1975 resulted in a Rc65 blade after tempering. This one (1925f) should be about Rc63 on fresh steel. 1935 would probably give me Rc63/64. I’m probably 1/2 Rc point off of the desired Rc63/64 to match my previous samples. I typically see one additional Rcpoint when I grind the surfaces clean, but in one case I saw an increase of two Rc points, but I think I had foil that wasn’t fully sealed on that one. Larrin, am I correct to assume the cryo converted enough of the retained austenitite that the high temper didn’t bump the hardness as much as it would have with no cryo?
The no cryo, high temper condition came out at Rc61.5, so probably Rc62.5 when clean. I used 1990f. I probably should have used 2000f, or even 2025f. I used four tempers at 1000f.
Z-FiNiT is tempering now. I left the samples in cryo for 48h. Chuck at AKS told me this steel serms to prefer long cryo soaks, and I didn’t pay enough attention to my equipment needs, as I was tempering the no cryo z-wear samples yesterday for 8h.
