Carbide tear-out questions

Great pics!
second pic above). But...far more common is the carbides blunting/glazing due to abrasive wear instead of abrasive shaping.
Either way it can be minimized or eliminated with good practices.
Common how we draw several conclusions when looking at the same photos. Trying to draw some similar elements into a conclusion: ToddS has
a point how a thin apex may tend to release carbides when the steel is flexed with wear and some sharpening. I don't have
a high VC steel in a medium flex fillet knife. I just have the very stiff blades in s30v, s60v and s90v. I've observed these steels wear just like
any other steel with use. (just cutting meat, trying not to hit bones) They develop a burr and then the edge will curl. This is the point the knife
expresses 'as dull' and I check it under 8X to see whats going on. It's always the same as any knife ( even with lessor steel) after use. That's what their edge looks like. This condition doesn't require the use of a flat stone to correct. One can merely ease the curl back straight with a
few light, careful strokes on a diamond rod. Or you can remove it by grinding it off on a flat stone. Which I think is not the better approach. All normal. Does this stressing of the metal cause carbide tear out? Would it matter if it did? I know I would not notice. I would go on using it as now I have a sharp knife and I go back to work. Just me, but it is still good to know these gents studied for these conclusions. Thank you for these very good photos and writing. DM
 
Last edited:
I also think it's pretty self-evident that quite a few people are reporting worse edge longevity when some of these steels are sharpened on non-diamond abrasives. Size and variety of carbides is another factor

I'm definitely not that knowledgable on the subject but, ^^^^^this.

I can't get a decent edge on D2 no matter what unless I use diamond. The opinions on the reason for this are fascinating though... carry on.
 
anyone want to start making comments on this video to help him out. i feel like he doesnt understand what most are saying.

 
anyone want to start making comments on this video to help him out. i feel like he doesnt understand what most are saying.

Hi,
Thats kind of ... random ;)

Comment to say what to the guy exactly?
Maybe what "most are saying" is nonsense (what is that)?
Maybe the guy is not interested in hearing the message?

Scanning the first minute of transcript says to me this video is not for me :)
but name was familiar, turns up
comments on sharpening maxamet , exchange between, Michael Elmer from Crazy Sharp, Big Brown Bear, Cliff Stamp, ...
 
First off I'm in no way claiming to have extensive knowledge in the field of metallurgy. However I did take a couple of metallurgy classes when I was in CNC training but those two classes were like a "101 & 102" type classes that truly taught the bare basics of the subject. I did have an instructor in both classes that I truly believed did know his stuff really well.

OK with that said I guess it's fair to say that I probably know enough to be dangerous :eek:. But this concept of "carbide tear out" is something I never heard mentioned in any of the classes I took> and after looking in my text books I couldn't find it in either one of them. But in all fairness we really didn't focus all that much on cutlery steel per se>>actually the two classes focused on a wide range of metal properties and applications in general.

Now I do much of my finish work on my blades with a Spyderco Ultra-Fine stone in many cases and I've only had really nice results in a wide range of cutlery steels. Which would leave me to believe that I haven't had the problem of "carbide tear out" But I don't have a dissecting microscope to actually determine that one way or the other. So what would the main signs of "carbide tear out" indicate with sharpening many of these newer/better supersteels? And for the record I own M390, S110V, S90V, ZDP-189 ect, ect.
 
JD, don't feel out of line with the rest of us. The few guys that are knowledgeable on here about this subject have access to a SEM and examine
their knives with it. Plus, I can tell from their writing they may have a Engineering degree. Which adds to their understanding of the subject.
My degree didn't go into that area and I struggle with some of their writings but I can grasp their main point. Thus, I'm glad we have the
caliber of folks we do on this Forum.
Some say that Spyderco stone is not hard enough to sharpen the vanadium carbides. DM
 
I'm of the belief that carbide tear-out can happen; it's not hard to imagine how it could, and there's at least some evidence it likely does happen. But I'm also of the belief that 99.999% of us will likely never actually see it (in proof), if/when it does happen. With most of the carbides in modern cutlery steels being so small (~ 5µ or less, in PM-process steels), one would need access to SEM technology or high-mag, high-res microscopy to verify it anyway. Otherwise, by simple cutting tests or naked eye/low-mag examination, we'd only be able to chalk it up to simple edge wear, or maybe 'chipping' (or 'micro-chipping'), with no way of knowing or definitively proving how that wear or chipping got started in the first place.

In an industrial/manufacturing environment, where a manufacturer may have their own FA (Failure Analysis) lab with a SEM on-site, they could use that resource to analyze why cutting tools might be wearing faster under particular uses or maintenance schemes. It's been mentioned that inadequate abrasives might increase the likelihood of matrix steel being eroded from around carbides near the tool's edge, while at the same time also failing to shape/thin the carbides themselves. That's when edge durability suffers as the support for carbides near the edge degrades, and the carbides eventually have nothing left to hold onto; so logically, they fall out or 'tear' out under stress, leaving the cutting edge less-refined than may be ideal. For us hobbyist knife/steel enthusiasts, we might only notice that we need to touch up more frequently (on our ceramic tools, maybe) to keep our knives as sharp as we want. AND, it may never occur to us to think why that is so, and most of us won't likely care either, nor really need to, in our simple, infrequent uses of our cutting tools.

But in a manufacturing/high-volume/high-expense environment, an mfr might notice their tools need resharpening more frequently (resulting in more production downtime > lost revenue), and/or need replacement more frequently (more capital expense) than what they consider reasonable or normal. Perhaps they also notice a faster degradation in manufactured product tolerances or finish (effects of cutting tools not cutting so cleanly or precisely anymore). Maybe they notice this after they've recently changed maintenance schemes to less expensive sharpening materials/methods, etc, and they're wondering if/how that affected tool life & performance in use. I could see at that point, where they could start pulling tools from the line periodically to monitor how they're wearing in use, with examinations in the SEM or by whatever other hyper-accurate analysis is useful. That's when it might actually be proven if they can actually SEE an increased frequency/number of empty 'divots' left by dropped carbides at tool edges under microscopic examination, and/or hanging carbides that look like they're not being shaped or refined very well at the edge. That's when they might starting rethinking how they're maintaining the tools.
 
Last edited:
Some say that Spyderco stone is not hard enough to sharpen the vanadium carbides. DM

That's 'cause they aren't. They can abrade the steel substrate, but not the carbides themselves. They'll put some degree of wear on them, but it'll be rounding them from wear rather than shaping them by cutting. Vanadium carbide is harder than aluminum oxide by a not-insignificant margin. :)
 
  • Like
Reactions: Mo2
Ok, thanks 42. I suspect a Spyderco ceramic is a little harder than a Norton India. DM
 
Ok, thanks 42. I suspect a Spyderco ceramic is a little harder than a Norton India. DM
Harder in terms of bond strength and density by a significant margin, but the hardness of the abrasive grains is roughly equal. There is some variation in the specific hardness of various grades of aluminum oxide (or any other abrasive) but it's still all in the same ballpark. The hardness of the bond strength has no impact on the ability of the abrasive to cut vanadium carbide.
 
Ok, thanks for this writing as I was unsure where it sat above the India. DM
 
Last edited:
Aluminum oxide is pretty much aluminum oxide. The difference between an India hone and a Spyderco hone is pretty much down to the binding method, like 42 mentioned. India hones are composed of loose aluminum oxide particles mixed with a binder and pressed into the shape of a hone. They will shed particles as the particles dull and get torn loose. Spyderco's hones are mostly just the abrasive particles (perhaps with a small addition of something to help them fuse), pressed and heated to the point that they fuse together. Very little of this will come loose over the life of the hone.
 
We need to understand that a theory without a solid study backing it is just a theory. The problem is that I highly doubt that someone has time, resources and knowledge to do a study on how different abrasives of different hardness with different bonds affect different steels (low-high hrc) that has different carbide percentage of various sizes in non-industrial applications. It is a very interesting theme, but without more research, it is just opinion against opinion. It's like a debate between a Christian and a Muslim. Both have strong beliefs/opinions backed with very few questionable facts. I am forced to put this book on the shelf. Until some more useful data will come.
 
customLogo.gif


Sisyphus, rolling the carbide back up to the apex...
 
For punishment Sisyphus was sentenced to a life of rolling a boulder up a mountain. Only to see it roll down again. For some reason the Greek
Gods were angry at him. DM
 
For punishment Sisyphus was sentenced to a life of rolling a boulder up a mountain. Only to see it roll down again. For some reason the Greek
Gods were angry at him. DM

If Sisyphus were around today and a member of this board, he'd be sentenced to an eternity of sharpening blades only to have them immediately dull upon completion. :p
 
Back
Top