least chippy super steel

CPM 3V with a heat treat optimized for cutlery shows very little edge chipping, even at HRC 61-62. The only steel I've played with better resistance to chipping without being soft and mushy is INFI. That said, steels like V4E and 4V show less edge damage than 3V or Infi in rough use and thin edges at working hardness over HRC 62, which is why it has beat out M4 as the steel of choice being used in the world cutting championship. Even though the failure mode is chipping, it takes a tremendous amount of abuse to get there. This is in reference to an optimized heat treat such as the knives being used in the cutting competitions, which is significantly different from the HT prescribed for it in the data sheet. If someone is using a 4V or V4E knife that is chippy I can almost guarantee it was heat treated to the data sheet, which results in a crumbly edge. The knives being used in competition, even though they're frequently very hard, are not heat treated that way and don't behave like that.
 
Simply because they are austenitized at the lowest possible temperature to still achieve a desired hardness/strength.
This approach will increase an impact toughness of any heat treated steel. Sad is this is not done in production knives.
 
JSCT said:
Simply because they are austenitized at the lowest possible temperature to still achieve a desired hardness/strength.
This approach will increase an impact toughness of any heat treated steel. Sad is this is not done in production knives.
Click to expand...

Nope, that's not the answer. I understand why you might think that (the data sheet says that), but that's not it. There is not a lot of correlation in "toughness" (joules of energy absorbed in an impact fracture) and the durability and "toughness" of an edge. I think it actually has more to do with forming a strong even homogeneous microstructure. This is not very important in a stamping die where things like retained austenite actually make the tool more durable but the situation changes in a knife edge. We've been testing 4V and V4E here this winter and are several generations into it (many many test blades) and have looked at austenitizing temperatures well under 1900 and well over 2,000 and everything in between and the best edge durability isn't at the low end.
 
IIRC problems with S30V chipping turned out that it requires a broader cutting angle and that solved the chipping problem. Angle , shape , and hardness - different for different steels for optimum performance !!!
 
Didn't the additional of a small fraction of niobium which replaced a little bit of the vanadium solve that problem? That makes me wonder if something other than the generally known grain size controlling properties of vanadium were at work? I have heard good things about Niolox which is a cast stainless steel that supposedly has good toughness and abrasion resistance in knifey applications.
mete said:
IIRC problems with S30V chipping turned out that it requires a broader cutting angle and that solved the chipping problem. Angle , shape , and hardness - different for different steels for optimum performance !!!
Click to expand...
 
I have heard that Busse leaves their edges pretty thick for ultimate toughness, but I have also seen some people committing the cardinal sin of of removing the blade coating and thinning the edge with good results. Do you think that INFI has the same fine edge stability say as low tempered 3V or even Busse's own 52100 recipe?
Nathan the Machinist said:
CPM 3V with a heat treat optimized for cutlery shows very little edge chipping, even at HRC 61-62. The only steel I've played with better resistance to chipping without being soft and mushy is INFI. That said, steels like V4E and 4V show less edge damage than 3V or Infi in rough use and thin edges at working hardness over HRC 62, which is why it has beat out M4 as the steel of choice being used in the world cutting championship. Even though the failure mode is chipping, it takes a tremendous amount of abuse to get there. This is in reference to an optimized heat treat such as the knives being used in the cutting competitions, which is significantly different from the HT prescribed for it in the data sheet. If someone is using a 4V or V4E knife that is chippy I can almost guarantee it was heat treated to the data sheet, which results in a crumbly edge. The knives being used in competition, even though they're frequently very hard, are not heat treated that way and don't behave like that.
Click to expand...
 
jdm61 said:
I have heard that Busse leaves their edges pretty thick for ultimate toughness, but I have also seen some people committing the cardinal sin of of removing the blade coating and thinning the edge with good results. Do you think that INFI has the same fine edge stability say as low tempered 3V or even Busse's own 52100 recipe?
Click to expand...

Busse knives are thick and aren't tuned for optimal cutting performance, but like you say are more oriented towards "ultimate toughness", but INFI will out perform industry standard 3V and is very close to the edge stability of optimized 3V when thinned out to identical geometry. It is definitely a good performer. It's not in the same class as optimized 4V or V4E for edge durability, but it's also much more ductile with higher impact toughness and nearly unbreakable so they're really not analogous materials. Short answer: yes Infi has good edge stability.
 
Nathan the Machinist said:
Nope, that's not the answer. I understand why you might think that (the data sheet says that), but that's not it. There is not a lot of correlation in "toughness" (joules of energy absorbed in an impact fracture) and the durability and "toughness" of an edge. I think it actually has more to do with forming a strong even homogeneous microstructure. This is not very important in a stamping die where things like retained austenite actually make the tool more durable but the situation changes in a knife edge. We've been testing 4V and V4E here this winter and are several generations into it (many many test blades) and have looked at austenitizing temperatures well under 1900 and well over 2,000 and everything in between and the best edge durability isn't at the low end.
Click to expand...

Not sure what is in the datasheet :D As I take them only little into consideration :) There definitely is an microstrength importance
- measured by depth of a nanoindenation. And so there definitely exists a microtoughness which I am not aware was ever tested.

I think better results showed up at higher aust temps simply because with freezing it allows to go higher strength with minimum
of retained austenite so it had more of durabilty you mentioned.

Can you explain a little what you mean by that durability ? some combination of edge retention at cutting and toughness at chopping ?
Which tasks the blades performed ?
 
jdm61 said:
Didn't the additional of a small fraction of niobium which replaced a little bit of the vanadium solve that problem? That makes me wonder if something other than the generally known grain size controlling properties of vanadium were at work? I have heard good things about Niolox which is a cast stainless steel that supposedly has good toughness and abrasion resistance in knifey applications.
Click to expand...

I am currently making 3 gyutos out of niolox will surely upload some pics. Yes it can take a thin geometry and much lower angles
than S30V for obvious reasons I will try to get 61+ HRC out of it..

btw: spyderco nilakka was an excellent example of improper material selection for knife geometry.
original design used by Pekka Tuominen used RWL-34 a high strength steel at 62HRC so obviously
it could take a lower angle than S30V with spydercos ht at 59-60 or so..
 
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