High HRC is not equal high wear resistance

[ferider]

Pretty obvious when i compare my rex45 and cruwear pm2 in use. I have to sharpen rex45 more often.

Of course its nice to have a hard knife.

Discuss :)

[DOUBLE D]

That seems shocking that you would have to sharpen rex 45 more often. I am interested in why that would be!

[A.S.O.K.A]

My rex45 has proven to have a little more wear resistance than my M4. But my M4 has better impact resistance than my rex45. Also, my rex45 responds better to stropping than my M4. Both knives are Para3s

[Pelagic]

I find it hard to believe that Rex 45 at 66 HRC has noticeably less edge retention than cruwear at 61-62 HRC. That is an extreme difference in hardness.

I know HRC isn't everything, so whoever is waiting to bash me as if I believe that, calm down. But cut tests almost always reveal that HRC and edge retention are directly correlated.

[ferider]

I find it hard to believe that Rex 45 at 66 HRC has noticeably less edge retention than cruwear at 61-62 HRC. That is an extreme difference in hardness.

I know HRC isn't everything, so whoever is waiting to bash me as if I believe that, calm down. But cut tests almost always reveal that HRC and edge retention are directly correlated.

Not bashing you, and maybe im treating my rex45 pm2 harder than my beloved Cruwear one. But also Ankersons cutting tests show the softer s110v military way above the harder Rex45 one. Why ?

[ZrowsN1s]

Carbide volume, grain size, heat treat protocol, geometry.....so many factors. High HRC is just one variable among many. One 60 HRC knife is definitely not automatically equal to another 60 HRC knife with different variables. Got to look at the whole picture :D

[Deadboxhero]

Edge finish and cutting style.

220- 400 grit with a draw slicing motion

More of the harder carbides are exposed with a rougher finish at the teeth of the edge.

Take s110v and Jack it to 65 with a boutique HT and you'll smoke the softer s110v.

So hardness has a place for edge performance

A stronger matrix holds the carbides better also.

So harder matrix can support thinner blade grinds and support thinner edges angles but is an inverse relationship with pure durability.

So either use a knife like a knife and be rewarded with more performance. Or use like a hammer and be punished with thicker geometry that doesn't cut very good but doesn't break for ridiculous non knife uses

[Bill1170]

Edge finish and cutting style.

220- 400 grit with a draw slicing motion

More of the harder carbides are exposed with a rougher finish at the teeth of the edge.

Take s110v and Jack it to 65 with a boutique HT and you'll smoke the softer s110v.

So hardness has a place for edge performance

A stronger matrix holds the carbides better also.

So harder matrix can support thinner blade grinds and support thinner edges angles but is an inverse relationship with pure durability.

So either use a knife like a knife and be rewarded with more performance. Or use like a hammer and be punished with thicker geometry that doesn't cut very good but doesn't break for ridiculous non knife uses

Yup. Well said.

[ferider]

So either use a knife like a knife and be rewarded with more performance. Or use like a hammer.

Well, yeah, well said; except - this might be entirely me - I missing an answer to my question. I am comparing two knives with identical geometry in practical use (PM2), wasn't using them as hammer or prybar. Cutting greens in the yard, a few boxes for recycle, cutting electrical cables and getting rid of isolation, cutting brass connectors out of a hose, etc. After a day like that I have to resharpen the Rex45 PM2, the Cruwear one holds a couple yard days instead. I had a Cruwear Manix 2 camping for a week, and the edge did not reflect light on our return.

And, from https://www.bladeforums.com/threads/ran ... ope.793481

CPM S110V - 1080 - Spyderco Military - 63-64 RC - .020" Behind the edge
: : :
REX-45 - 840 - Spyderco Military - (? HRC) - .023" behind the edge

From viewtopic.php?f=2&t=83847

REX45 Military - (66.3 - 67) HRC (at least 2 Rockwell points higher than the s110v Military, but wear resistance is 25% lower).

What's up with that ? What does that have to do with anybody using a knife not as a knife ?

Roland.

[Banter 247]

So either use a knife like a knife and be rewarded with more performance. Or use like a hammer.

Well, yeah, well said; except - this might be entirely me - I missing an answer to my question. I am comparing two knives with identical geometry in practical use (PM2), wasn't using them as hammer or prybar. Cutting greens in the yard, a few boxes for recycle, cutting electrical cables and getting rid of isolation, cutting brass connectors out of a hose, etc. After a day like that I have to resharpen the Rex45 PM2, the Cruwear one holds a couple yard days instead. I had a Cruwear Manix 2 camping for a week, and the edge did not reflect light on our return.

And, from https://www.bladeforums.com/threads/ran ... ope.793481

CPM S110V - 1080 - Spyderco Military - 63-64 RC - .020" Behind the edge
: : :
REX-45 - 840 - Spyderco Military - (? HRC) - .023" behind the edge

From viewtopic.php?f=2&t=83847

REX45 Military - (66.3 - 67) HRC (at least 2 Rockwell points higher than the s110v Military, but wear resistance is 25% lower).

What's up with that ? What does that have to do with anybody using a knife not as a knife ?

Roland.

HRC is matrix hardness. A given sample, within a useful range of hardness, will gain wear resistance with higher hrc. But, comparing two compositions, that hardness won’t necessarily overcome carbide. Carbides are the difference, here. That’s what Deadbox Hero was alluding to. (See also: nitrides)

So... LC200N at 58 will smoke AEB-L at 60, assuming the same geometry, because LC200N is leaning on nitrides, while AEB-L read about carbides in a book in a long, hot summer around 1973.

[ferider]

HRC is matrix hardness. A given sample, within a useful range of hardness, will gain wear resistance with higher hrc. But, comparing two compositions, that hardness won’t necessarily overcome carbide. Carbides are the difference, here. That’s what Deadbox Hero was alluding to. (See also: nitrides)

So... LC200N at 58 will smoke AEB-L at 60, assuming the same geometry, because LC200N is leaning on nitrides, while AEB-L read about carbides in a book in a long, hot summer around 1973.

Thanks, got it. So M4 or even M2 at - say - 64 can have similar or more wear resistance than Rex45 at 67, as M[24] have more carbides ?

[ferider]

And finally, do you agree with Crucible that CPM 20CV at 58 HRC (while this might not be optimal) has as much wear resistance as CPM m4 at 63 HRC ? Or are they over-selling one of their steels over another one ?



Thanks,

Roland.

[Pelagic]

And finally, do you agree with Crucible that CPM 20CV at 58 HRC (while this might not be optimal) has as much wear resistance as CPM m4 at 63 HRC ? Or are they over-selling ?



Thanks,

Roland.

I wonder in what context they were making that statement. In folding knives (edge retention), I'd seriously doubt that was the case. There's not a big enough difference in those 2 steels carbide-wise to overcome that huge difference in matrix hardness.

[Banter 247]

HRC is matrix hardness. A given sample, within a useful range of hardness, will gain wear resistance with higher hrc. But, comparing two compositions, that hardness won’t necessarily overcome carbide. Carbides are the difference, here. That’s what Deadbox Hero was alluding to. (See also: nitrides)

So... LC200N at 58 will smoke AEB-L at 60, assuming the same geometry, because LC200N is leaning on nitrides, while AEB-L read about carbides in a book in a long, hot summer around 1973.

Thanks, got it. So M4 or even M2 at - say - 64 can have similar or more wear resistance than Rex45 at 67, as M[24] have more carbides ?

I’m not especially familiar with Rex 45 or Cruwear.

When talking about carbides, there are matters of size, hardness of the carbide itself, distribution, shape/formation, etc. Chromium carbides are larger than the smaller vanadium carbides, for example. There’s also volume, or what % of the steel is represented by carbide.

In general, high volume of homogeneously distributed, harder carbide -> greater wear resistance, and harder matrix between the carbides -> greater wear resistance.

For more specifics on quirks of a given composition, Deadbox Hero or Larrin are the people to ask, if they are available.

[Deadboxhero]

So either use a knife like a knife and be rewarded with more performance. Or use like a hammer.

Well, yeah, well said; except - this might be entirely me - I missing an answer to my question. I am comparing two knives with identical geometry in practical use (PM2), wasn't using them as hammer or prybar. Cutting greens in the yard, a few boxes for recycle, cutting electrical cables and getting rid of isolation, cutting brass connectors out of a hose, etc. After a day like that I have to resharpen the Rex45 PM2, the Cruwear one holds a couple yard days instead. I had a Cruwear Manix 2 camping for a week, and the edge did not reflect light on our return.

And, from https://www.bladeforums.com/threads/ran ... ope.793481

CPM S110V - 1080 - Spyderco Military - 63-64 RC - .020" Behind the edge
: : :
REX-45 - 840 - Spyderco Military - (? HRC) - .023" behind the edge

From viewtopic.php?f=2&t=83847

REX45 Military - (66.3 - 67) HRC (at least 2 Rockwell points higher than the s110v Military, but wear resistance is 25% lower).

What's up with that ? What does that have to do with anybody using a knife not as a knife ?

Roland.

It depends on how they were sharpened. The Rex 45 and Cruwear are close but the Rex45 is run harder.

[Banter 247]

And finally, do you agree with Crucible that CPM 20CV at 58 HRC (while this might not be optimal) has as much wear resistance as CPM m4 at 63 HRC ? Or are they over-selling one of their steels over another one ?



Thanks,

Roland.

I’m unsure of how they express *wear resistance* in machining and industrial application, but in the context of cutlery, M4 at 63 will out perform 20CV at 58 in terms of edge retention vs cardboard or similar commonly cut media.

[Deadboxhero]

Yea AEB-L or 52100 at 64rc will not out cut s110v at 59-60rc on rope .

Yet, s110v at 59-60 isn't going to have the best edge retention for all circumstances and users either so it just depends.

Edge finish eludes most people but is a significant factor in how the edge performance is expressed.

Along with if the edge is being used in a drawing slice or saw motion or pushing straight down with a "push"

Will show benefits with a certain edge finish and some steels have better synergy with one finish or either.


S110v is capable of going harder but it becomes less forgiving to improper abrasives and abuse so it's a trade-off for more horsepower.

You'll probably only ever find from a very experienced and knowledgable custom maker that is a glutton for pain and that knows his customer can handle it.


It doesn't have to be some kind of battle between choosing wear resistance and hardness, one can have both if they don't use it like a hammer.


Sometimes less carbides and just high hardness is best.
Preference is king after all.

It's silly to use these industrial graphs for pointing out edge performance differences. The makers of those graphs never intended them to be applied to sub micron knife edges besides None of those tests where done with knife edges. It's for parts. Knives don't pay the bills to keep the lights on for all the testing and process they do and the volume of steel they need to sell. These graphs are for industrial purposes and giving a rough idea, Not gospel.

[ferider]

These graphs are ... Not gospel.

True and point taken.

But neither is the HRC number all by itself, as obvious after this thread.

Case in point: I've been using this Hinderer XM-18 Wharncliffe all day in the yard yesterday; I love that knife, the way it handles, does things (yesterday was electric cable and box cutting again), and how I can blindly handle it. When I put the knife away at night, still quite sharp, I was wondering if the fact that Hinderer hardens their 20cv to HRC 59-60 should bother me. I decided it should not. The knife works.

Roland.

[Larrin]

Rockwell Hardness is the Megapixels of Knife Steel Specs: https://knifesteelnerds.com/2018/11/12/ ... -hardness/

[Skywalker]

When I put the knife away at night, still quite sharp, I was wondering if the fact that Hinderer hardens their 20cv to HRC 59-60 should bother me. I decided it should not. The knife works.

Roland.

That's what I find kind of funny about the recent M390/20CV/204P uproar. It doesn't seem to have been sparked by people upgrading from VG10 or 14C28N or S30V and not being happy in use, but from repeated cardboard cut tests. Doesn't mean the tests are bad or worthless, just that they might not be representative of how some people are using knives in those steels day-to-day (that, or no-one's actually using them... separate issue ).

I've got two M390 knives that I've used a decent amount - a Para2 from the first run, and a Benchmade 710DLC-1. Both of those are from ~2011-12. Spyderco had previously only done the M390 Mule; Benchmade only a gold class and another couple small-run limiteds, and then they were still warping blades on the 581 a couple years later. So there's a decent chance that the HT on either isn't as dialed in as we'd expect today.

Each was a definite, noticeable upgrade from the VG10, AUS8, and 14C28N I had been using before, and they've consistently remained better than the D2, S30V/S35VN, XHP, etc. I've used since. Both sharpen more easily than the S90V in my Sprig. Absolutely no idea what the HRC on either is, but the PM2 is always going to be in my EDC lineup and even the Sprig hasn't bumped the 710 as hunting knife of choice. No qualms about buying M390/204P/20CV or whatever else they want to call it from Spyderco or BM since, published HRC range or not.

Like you say - the knives work!