Hardness vs Wear Resistance?

[Lenny]

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

 

[hardheart]

more and harder carbides

 

[knarfeng]

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

more and harder carbides

For for the basic question, Wear Resistance is more related to composition than to hardness. Increased hardness has a much larger impact on lack of edge deformation than on wear resistance.

IMO edge retention is a combination of wear resistance and an edge that does not deform.

• If you compare the edge retention of two blades of the same alloy, one at ~56 and one at ~58, the blade hardened to a 58 will have better edge retention.
  
• If you compare the edge retention of two blades of different alloys, but the same hardness, the blade made from alloy with higher carbide content will hold an edge better because it has better wear resistance.

I have done both of these comparisons in my own testing. So to me this is more than theory.

For the specific example you give, I agree with hardheart. S30V has more carbides than 440A. Carbides provide more wear resistance.

There are more factors to edge retention than alloy composition and hardness, but you did not ask about those, so we won't go there right now.

 

[Folderguy]

For the specific example you give, I agree with hardheart. S30V has more carbides than 440A. Carbides provide more wear resistance.

How about a comparison between say a 154 CM hardened to 61-62 RC, versus a similar blade in S30V. Will the S30V last/retain a razor sharp, hair popping edge noticeably longer than the blade in 154 CM?

 

[Jason B.]

How about a comparison between say a 154 CM hardened to 61-62 RC, versus a similar blade in S30V. Will the S30V last/retain a razor sharp, hair popping edge noticeably longer than the blade in 154 CM?

Steels like S30V loose their sharp edge the fastest.

 

[Folderguy]

Steels like S30V loose their sharp edge the fastest.

That's very interesting. Why then are they considered by some to be a super steel?

 

[RevDevil]

That's very interesting. Why then are they considered by some to be a super steel?

Based on what I've learned so far, they aren't really, but when you compare them to 440a it's miles of difference. Aside from that S30V was specifically designed for the cutlery industy, lots of other steels (52100, M4, D2, O1) originally got their introduction in the world of industrial manufacturing (as dies, molds, steel used to cut other steel and hard materials, etc). Super Steel is a term that is loosely used to describe the latest and greatest steels.

 

[singularity35]

So what is a "super steel"?

 

[marcinek]

So what is a "super steel"?

Whatever is newest and most expensive. Lots of letters in the name helps, too.

 

[Noctis3880]

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

That would be the carbides in the steel itself. Think of it like concrete in a sidewalk. The cement itself would be worn away from everything walking(and rolling) on it, but the crushed stones are a lot harder and that gives "wear resistance".

Still, I find that hardness itself has a role in wear resistance. If the steel itself is harder, then it also becomes more wear resistant, albeit not as much as the carbides themselves. Still, it's pretty consistent that a wear resistant steel becomes more wear resistant the harder it is(S30V at Rc 62 vs S30V at Rc 57).

 

[knarfeng]

Steels like S30V loose their sharp edge the fastest.

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:

 

[Jason B.]

That's very interesting. Why then are they considered by some to be a super steel?

To me hardness and wear resistance are not to be thought of as a combined force but as two factors. Hardness I see as more resistant to impact while I view wear resistance as how difficult it is to grind away. A increase in hardness will bring more wear resistance but its not the same as adding large amounts of hard carbides to increase what I guess you could call its "standing" wear resistance.

They are considered to be super steels because even though the edge will not shave no more it still retains a V shape better and when it wears it becomes toothy. Its what most would call a working edge.

Here is a pic of S90V after some intense cutting, this edge would not even grab hair but would still slice paper and tomatos, cut rope.....

Note this edge has a microbevel so small it can not be seen by the naked eye, this knife cut drywall, cardboary, and many other items.

In some of the less damages sections you can see a balling of the metal. This is what typical wear looks like and the toothy/rough feel you get on your fingers.

This pic is AUS-8 at a high hardness after cutting manila rope. This shows better the balling effect. (little fuzzy )

 

[ono724]

Whatever is newest and most expensive. Lots of letters in the name helps, too.

LOL, awesome answer! :thumbup::thumbup:

 

[Nebulae]

wow we've got quit a bit of stuff going on here so I'll just throw in my $.02

first off we've got to define our terms. we've got hardness, wear resistance, and edge properties. All of these are highly correlated, but there is not necessarily a cause and effect relation ship. So...

difference between the same steel at different hardness-
harder steel is more wear resistant. usually much more I've been told it is an exponetial relationship, so 1 or 2 Rc point can make a big difference. this is probably because the harder steel matrix resists wear better, and the harder matrix does a better job of holding on to the carbides.

Different steels Same hardness-
carbide volume is king. The steel with more harder carbides will resist wear better.

Edge properties. This is tough and I have little real experience, so take it with a grain of salt.
The steel with the best wear resistance as measured by weight loss against an abrasive media may not be the steel with the best edge retention. Carbides may make it harder to sharpen, thus lending a seemingly duller edge, or they may just fall out. Since we are talking about very thin angles, large carbides can actually be pulled out of the matrix leaving gaps behind. Edge geometry, carbide volume, carbide size, and steel hardness all effect edge retention. I think we all know that different steels perform better at different angles, and levels of sharpness. Here we get into the shaving edge vs the toothy edge debate.

 

[Justin King]

Just to further complicate the discussion, not all carbides are of equal hardness, or of equal size, so to say that the steel with more carbides is more wear resistant is not always going to be correct. Lots of coarse carbides can also make an edge prone to micro-chipping, which does not necessarily equate to lower wear resistance but does equate to rapid edge degradation under cutting stresses.

 

[Gator97]

Whatever is newest and most expensive. Lots of letters in the name helps, too.

Agreed on the first part, as for the lots of letters, you should check out French(AFNOR) steel names - Z160WKVCD10-08-05- 04-02, Z85WDKCV 06-05-05-04-02, X160CrMoV12-28 instant supers

 

[Ankerson]

Also taking the same steel, say something like S30V and 2 blades at say 60 HRC one blade can hold the edge a lot longer than the other if one of them has too much retained Austenite.

 

[Ankerson]

Whatever is newest and most expensive. Lots of letters in the name helps, too.

Not all the time.

S90V has been around for 15 years..

 

[tiguy7]

Iron carbides are part of the matrix that resists the penetration of the diamond pyramid in the Rockwell hardness tester. Iron carbides can be as hard as the low 60's on the C scale (RWC). Tungsten carbide weighs in at 72 RWC. Vanadium carbide at 82 RWC. These hard included carbides do not resist the penetration of the hardness tester. They are pushed aside. They do resist abrasive wear much like stones in cement. Super steels have oodles of hard carbides among other things. They also tend to have small grain size and high purity.

 

[Ankerson]

Here is S90V after cutting a lot of rope, you can see the working edge forming here. This edge is still extremely sharp, will still slice newsprint easy.

Blown up here.