Hardness vs Wear Resistance?

[singularity35]

So I guess that letters and numbers in the name, and date of birth don't a supersteel make.

 

[Ankerson]

So I guess that letters and numbers in the name, and date of birth don't a supersteel make.

I believe it has more to do with performance than when a steel came out or how many letters or numbers it has.

Some steels like CPM-S90V, CPM-10V, CPM-S110V have been around for awhile and to this day they are still at the top of the heap.

 

[Jason B.]

Carbide tear out is something that once sounded good to me but after looking REAL close at a edge I don't see this effect. And if its so small that you can't see it at the above levels it probably has minimal effect compared to the larger damage happening around it. Deformation and abrasive wear seem to make up 95% of all edge damage, the last 5% is micro chipping/fracturing and deformation followed by tear out.

Fracturing, chipping, tear out, are all things you don't really want to happen at the edge. Through better heat treatments and more highly refined and pure (clean) steels we get closer to perfect edge wear and resistance to all unwanted factors. One problem that still remains though is that a factory HT in no way compares to a custom makers HT and the difference is sometimes beyond belief.

I have another picture of the other AUS-8 blade with a standard factory HT I'll get up in the morning. The difference is very shocking.

Super steels may not be as stable when thinned to a very small apex thus loosing the razor sharp edge but the added wear resistance prevents excessive material loss. If the geometry is held longer and the edge resists fracture and deformation better the knife will continue to cut longer. That does not mean it stays sharper (as in sharp feel) longer though.

 

[Ankerson]

Carbide tear out is something that once sounded good to me but after looking REAL close at a edge I don't see this effect. And if its so small that you can't see it at the above levels it probably has minimal effect compared to the larger damage happening around it. Deformation and abrasive wear seem to make up 95% of all edge damage, the last 5% is micro chipping/fracturing and deformation followed by tear out.

Fracturing, chipping, tear out, are all things you don't really want to happen at the edge. Through better heat treatments and more highly refined and pure (clean) steels we get closer to perfect edge wear and resistance to all unwanted factors. One problem that still remains though is that a factory HT in no way compares to a custom makers HT and the difference is sometimes beyond belief.

I have another picture of the other AUS-8 blade with a standard factory HT I'll get up in the morning. The difference is very shocking.

Super steels may not be as stable when thinned to a very small apex thus loosing the razor sharp edge but the added wear resistance prevents excessive material loss. If the geometry is held longer and the edge resists fracture and deformation better the knife will continue to cut longer. That does not mean it stays sharper (as in sharp feel) longer though.

Yes, you are correct in the differences between Production and Custom HT, they can be worlds apart for sure. There is a large difference between HT 200 blades at the same time and doing one or 2.

 

[Joshua J.]

So what is a "super steel"?

I would say that a "super steel" is simply a steel type that performs better than the average premium steel types (usually 440C or 154CM) in some way. CPM-15V is one of the most wear resistant steel types ever, and S-7 (designed for use in jackhammers) is probably the toughest steel there is. Then you have stuff like CPM-S30V which is a more generalized and less drastic improvement.

Super steels aren't new, most of them came about in the 70's and 80's for various industrial purposes (and then there's D-2, which is a world war 2 era steel).
Powder metallurgy is nothing new either, the earliest experiments coming from the early 1900's. After that it's a matter of refinement of the process and actually applying it to different industries.

The only reason you see so much hype about these things now is that they are finally being applied to knives. Only in the last 20 years has the steel industry taken any interest. In the 90's 154CM was a big deal, but guess what? It's made for the aerospace industry, we're just bumming it off them. Steel types like S30V represent a huge departure from the norm in that they are designed from the ground up to be used in knives.
The knife industry has this longstanding problem of being held back by the average user who does not know or care what a knife is made of, and manufacturers can only make what they can sell. If everybody scooped up every knife made of S90V the moment it hit the street, S90V would be much more common, and chances are we would have even better alloys like S110V and who knows what else all over the place. Unfortunately very few people can justify the cost of production using materials like that if sales aren't guaranteed.

 

[nozh2002]

OK, I've been wondering about this for some time.
What's the relationship between hardness and edge wear resistance?
Say we have 2 blades both hardened to RC 59; one is 440A, one is S30V.
What makes the S30V blade have better edge wear resistance than the 440A blade?
Lenny

Wear resistance is good for rail road or something this nature. CPM S30V has a lot of vanadium carbides - so it is like sandpaper or abrasive stone on the micro level. This does not directly mean good edge or good edge holding - CPM S30V show pretty average results and CPM S90V is not on the top eather, I guess those carbides tend to fall out from edge as sandpaper abrasive. While ZDP-189 with 65HRC actually performs best, so we may say that higher hardness - better edge retention. Until of course it is not overhardned.

Wear resistance means harder to grind and so for example nobody making knives from CPM S125V - even Spyderco gave up. Those knives in result costs higher with same performance.

However many steels can show excellent results without high hardness - like Dozier D2 or Custom made carbon steel knives - 1095, so this is not general rule.

Thanks, Vassili.

 

[Ankerson]

Wear resistance is good for rail road or something this nature. CPM S30V has a lot of vanadium carbides - so it is like sandpaper or abrasive stone on the micro level. This does not directly mean good edge or good edge holding - CPM S30V show pretty average results and CPM S90V is not on the top eather, I guess those carbides tend to fall out from edge as sandpaper abrasive. While ZDP-189 with 65HRC actually performs best, so we may say that higher hardness - better edge retention. Until of course it is not overhardned.

Wear resistance means harder to grind and so for example nobody making knives from CPM S125V - even Spyderco gave up. Those knives in result costs higher with same performance.

However many steels can show excellent results without high hardness - like Dozier D2 or Custom made carbon steel knives - 1095, so this is not general rule.

Thanks, Vassili.

I bolded the one thing you got right in that post....

 

[Lenny]

Wow, awesome discussion guys. :thumbup:
But now I'm more confused than ever!
Lenny

 

[Ankerson]

Wow, awesome discussion guys. :thumbup:
But now I'm more confused than ever!
Lenny

To make it simple.

The higher the percentage of Carbides that are in the steel the more wear resistant it will be, wear resistance and edge holding are directly related. Now that's assuming a good HT and proper hardness.

 

[cziv]

Steels like S30V loose their sharp edge the fastest.

That sucks to hear. I have a few knives (Benchmades) in S30V and I thought it was good stuff. What's an optimal bevel for sharpening?

I have a new Demko custom coming in CPM 154, what's the best edge bevel for that one?

How come CTS-XHP or Duractech 20CV, like XM-18's are made of, not mentioned? I thought they'd be top notch steels.

Sorry for all of the questions.

 

[Ankerson]

That sucks to hear. I have a few knives (Benchmades) in S30V and I thought it was good stuff. What's an optimal bevel for sharpening?

I have a new Demko custom coming in CPM 154, what's the best edge bevel for that one?

How come CTS-XHP or Duractech 20CV, like XM-18's are made of, not mentioned? I thought they'd be top notch steels.

Sorry for all of the questions.

He is talking about that hair splitting edge, not overall cutting ability.

CTS-XHP is a good steel, it's a very agressive cutter and holds an edge well, about the same as ZDP-189 edge retention wise.

Duratech 20CV is also a great steel, Duratechs vers of M390 and at proper hardness is right up there towards the top of edge retention. It takes a good HT that really knows what they are doing to get the best out of 20CV and M390 as the tempering process is very involved.

CTS-XHP, ELMAX and ZDP-189 are in the same group edge retention wise.

 

[cziv]

He is talking about that hair splitting edge, not overall cutting ability.

CTS-XHP is a good steel, it's a very agressive cutter and holds an edge well, about the same as ZDP-189 edge retention wise.

Duratech 20CV is also a great steel, Duratechs vers of M390 and at proper hardness is right up there towards the top of edge retention. It takes a good HT that really knows what they are doing to get the best out of 20CV and M390 as the tempering process is very involved.

CTS-XHP, ELMAX and ZDP-189 are in the same group edge retention wise.

Thanks for the info. Figuring out steels is kind of difficult - this thread is very good. :thumbup:

 

[Ankerson]

Thanks for the info. Figuring out steels is kind of difficult - this thread is very good. :thumbup:

Learning is a never ending process when it comes to steels.

Then you throw in a Custom HT from a great heat treater that really knows how to push the limits and things really get interesting in a real hurry.

 

[dantzk8]

What's the relationship between hardness and edge wear resistance?

Hardness provides strength.

Wear resistance has to see with the type and the amount of the carbides.

Edge holding has to see with the wear resistance, the strength, the toughness and the stain resistance. More or less with each of those four points according to the use you have of the blade.

dantzk.

 

[Folderguy]

I agree with Knifenut. At least for me, High Carbide alloys don't really take a highly polished edge very well and when (if) they do, they won't hold it all that long. But they will take a lesser edge very well and will hold that edge a very long time.

Sort of like this freehand drawing:

So, when sharpening S30V, should a slightly coarser belt, say 240 or thereabouts, be used to get the blade pretty sharp, and somewhat toothy, followed with some judicious use of a sharpening steel to get the blade shaving sharp?

 

[Ankerson]

So, when sharpening S30V, should a slightly coarser belt, say 240 or thereabouts, be used to get the blade pretty sharp, and somewhat toothy, followed with some judicious use of a sharpening steel to get the blade shaving sharp?

I wouldn't go that far....

S30V will take a screaming sharp highly refined polished edge.

Now yeah once you get that hair splitting edge on there it will be gone after you cut the flaps off a box, but then that's the same for most other steels also.

The problem can be with the high Carbide steels is what some are using to sharpen them with and yes they take more time to sharpen and polish the edges.

They will take a highly refined edge, but you will run into the carbides so it takes more effort to get them that sharp.

 

[dantzk8]

So, when sharpening S30V, should a slightly coarser belt, say 240 or thereabouts, be used to get the blade pretty sharp, and somewhat toothy, followed with some judicious use of a sharpening steel to get the blade shaving sharp?

I've found that for S30V the best (at least for me) was to refine the edge with an XXFine DMT plate and stop the sharpening at that point.

dantzk.

 

[Folderguy]

I wouldn't go that far....

S30V will take a screaming sharp highly refined polished edge.

Now yeah once you get that hair splitting edge on there it will be gone after you cut the flaps off a box, but then that's the same for most other steels also.

What steels don't lose their screaming sharp edge after cutting the flaps off a box?

 

[Folderguy]

I've found that for S30V the best (at least for me) was to refine the edge with an XXFine DMT plate and stop the sharpening at that point.

dantzk.

I hear you, but I no longer use stones (or the DMT plates, except in an emergency) for sharpening. For me, it's the Worksharp without a doubt.

 

[Ankerson]

What steels don't lose their screaming sharp edge after cutting the flaps off a box?

I haven't found one yet, but I am still looking, I am sure there is one out there someplace.

I likely wouldn't want to sharpen it though because I am sure it would be a real PITA.

I am talking about that very fine screaming edge here, not just shaving sharp etc....