A8 mod testing

I'm no soyentist, but it looks like 1875F at 40 minutes followed by dry ice slurry or LN and 400F tempering is a safe bet for a balanced and efficient heat treatment.
 
HPD said:
Thank you for doing this! I have one question. You list 3VC and 3VHi with the same Aus. temperature in your original post (1950F). Was this was a typo?
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No typo: same 1950F aust, about 30 minutes soak (less than 1 minute delta), same -40C freezer (about same soak time), same tempered temp.
 
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A follow up on my mentioned about testing impact toughness with a thin bevel geometry 1095 felling axe.
Result = failed, sure it has plenty of toughness ;)... next, will try higher yield strength at same geometry. I think A8M would end up with similar result.
*note: no further follow up *

 
I heat treated a couple of blades last night. I did one A8Mod knife. I used 1875 for 40 minutes, continuous quench with plates and compressed air followed by dry ice/isopropyl slurry. I tempered at 300F for two hours and then back into the dry ice overnight. I am now doing a second temper at 380F. After the 300 temper I vigorously ran a 60 HRC file over the edge with only a tiny hint of material removed, practically unnoticeable. Thanks for all the information on this thread.
 
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I recently ran a batch of A8 Mod wth a slightly modified heat treat from what Ryan told me. I used cryo and a high temper and reached 60 Rc.

I have been testing an A8 Mod knife for the last week and yesterday compared it to a similar AEB-L knife. People often say fine edge stability suffers with a high temper, which is the case with some steels, but in this case I felt after carving on bone that the A8 Mod held up better than the AEB-L when looking at the edge under 100x microscope.
 
Seedy Lot said:
I recently ran a batch of A8 Mod wth a slightly modified heat treat from what Ryan told me. I used cryo and a high temper and reached 60 Rc.

I have been testing an A8 Mod knife for the last week and yesterday compared it to a similar AEB-L knife. People often say fine edge stability suffers with a high temper, which is the case with some steels, but in this case I felt after carving on bone that the A8 Mod held up better than the AEB-L when looking at the edge under 100x microscope.
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Maybe it’s just this steel that behaves like this. 3v does quite a bit better with a low temper. Same for ztuff. I did get more edge deformation with ztuff using a high temper. But i got an overall tougher blade from the high temper!
 
rodriguezryan14 said:
Maybe it’s just this steel that behaves like this. 3v does quite a bit better with a low temper. Same for ztuff. I did get more edge deformation with ztuff using a high temper. But i got an overall tougher blade from the high temper!
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You got an overall slightly better "wear resistant" blade with the high temper, at the cost of some apex stability. The seconardy hardening of the higher tempers robs the steel matrix of carbon to form tempering carbides, which increases wear resistance (slightly, as they are VERY small carbides, increasing the overall carbide volume of the steel).
 
Stuart Davenport Knives said:
You got an overall slightly better "wear resistant" blade with the high temper, at the cost of some apex stability. The seconardy hardening of the higher tempers robs the steel matrix of carbon to form tempering carbides, which increases wear resistance (slightly, as they are VERY small carbides, increasing the overall carbide volume of the steel).
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But what I’m trying to figure out is why some steels seem to gain more toughness with the high temper! And some lose it. Larrins tests show a lot of steels gaining toughness with the low temper. But in tests I’ve done, ztuff and A8 gain much more toughness with a high temper!! But yes, you lose that apex stability!! Just a little it seems. I couldn’t detect a loss on A8, but ztuff was noticeable!
 
Stuart Davenport Knives said:
You got an overall slightly better "wear resistant" blade with the high temper, at the cost of some apex stability. The seconardy hardening of the higher tempers robs the steel matrix of carbon to form tempering carbides, which increases wear resistance (slightly, as they are VERY small carbides, increasing the overall carbide volume of the steel).
Click to expand...
And that’s also a reason why some people prefer a high temper on 3v, it seems like it cuts better in skinning rolls. I know big chris uses the high temper a lot!! Maybe you’ll get more rolling of the edge. But if you adjust edge geometry enough, you’ll get a mean skinner out of it!
 
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