Sharpening high hardness and wear resistant steels

You didn't mentioned how exactly sharpen this S30V nor this blade hrc. Apex shows fractures. if much more stropping done, that extra proud on apex and smaller one next on the left are will be detach. Also look like many scratches lines created by detached carbides plowed the matrix. Strop added more variables and erase quite a bit of evident due to smoothing/erasing.

It would be great/cool if you SEM imaging this S30V (like pic below) after sharpened with 1K & 2K for SiC & diamond plate - 4 pics.

Spyderco S110V @62rc would be a good candidate for seeing affects of high carbide volume against sharpening abrasive.

ToddS said:
Can anybody point me to a type of steel (or ideally a very small folder made of that steel) and a sharpening technique that SHOULD cause "carbide tear-out" ?

I've shown these images before: S30V sharpened with an aluminum oxide ceramic (sintered) stone and then stropped on hanging denim loaded with Mother's Mag polish (aluminum oxide). You can see the vanadium carbides sitting a bit proud, simply because they abrade more slowly than the matrix.

s30v_06.jpg
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I read this thread at least twice and still don't really get it. I mean I understand the theory of abrading VC to shape the apex better, which AlOx or SIC etc. should not be able to or very insufficient be able to but diamonds should be.

Whys does it make a difference though how coarse the abrasive is? VC on that SEM picture are about 5 nm apart. A fine diamond compound is 0.25 micron (250 nm), means one particle covers about 50 VCs and 5 times as much "area" of matrix. Correct? So all VCs are "covered" by a large abrasive particle all the time, whether it's 250 micron or 0.25 micron!
 
SEM pics are in um (micro meter) not nm. 250nm diamond translate to cutting tips of 25-50nm depend on substrate & pressure.
awestib said:
I read this thread at least twice and still don't really get it. I mean I understand the theory of abrading VC to shape the apex better, which AlOx or SIC etc. should not be able to or very insufficient be able to but diamonds should be.

Whys does it make a difference though how coarse the abrasive is? VC on that SEM picture are about 5 nm apart. A fine diamond compound is 0.25 micron (250 nm), means one particle covers about 50 VCs and 5 times as much "area" of matrix. Correct? So all VCs are "covered" by a large abrasive particle all the time, whether it's 250 micron or 0.25 micron!
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bluntcut said:
When cutting has lot of draw and pull motions, these teeth will perform fine for cardboard & rope & etc
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Luong, I don't think I'm understanding what you mean here. Are you saying that the effects this phenomena would remain undetectable in high sharpness edge retention while cutting cardboard and rope? Even with an apex set on a ~3um abrasive? And that this is why i would need to use shaving pine or bamboo to test the apex strength between apexes set on AlOx, SiC, and Diamond?

bluntcut said:
Strop added more variables and erase quite a bit of evident due to smoothing/erasing.
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Wait a minute, I thought he effects of an abrasive not being able to cut vanadium were supposed to get worse the finer the AlOx abrasive used, and in particular were supposed to be most egregious when stropping high vanadium content steels using AlOx based stropping compounds on pliable substrates (at least according to this thread)?

If that were the case, shouldn't an s30v blade sharpened on a sintered ceramic aluminum oxide stone and then stropped using an aluminum oxide stropping compound on a hanging denim strop show very severe issues with this problem? Evidence that would be obvious and clearly visible in SEM photography (which is certainly more that 1000x more zoomed in than the USB microscope images I posted earlier)?
 
I'm not Jason, and rarely use my limited non branded waterstones, but I feel there's differences between HAP40, M4, and ZDP-189 I've been testing & using.
Perhaps it's more obvious if one wants high level if edge refinement, and not so obvious if 600 grits DMT or equivalent is the goal. Not saying 600 grit isn't capable of sharp, but I like it when my knives can dry shave my face. The three have differences that can be felt but hard to describe. It was also found when using it on soft material such as peeling mango or apple. The amount of push cut and sawing needed to complete the job gives different nuances.

All three were finished similarly up to DMT EEF.
 
I referred to ~12um abrasive. At 3um there will be smoothing/polishing, i.e. weakened carbides (barely hang on) will be gone and divots get smoothened/erased. Still there will be carbides stand proud - per Todds pic, that carbide protruding from apex is not strong - especially from lateral force, agree?

Strop added at least 4 major variables: flex; lapping; wax; substrate fuzz... so complexity goes way up. It is a sure way to raise massive noise over signal - so speak.

Steel_Drake said:
Luong, I don't think I'm understanding what you mean here. Are you saying that the effects this phenomena would remain undetectable in high sharpness edge retention while cutting cardboard and rope? Even with an apex set on a ~3um abrasive? And that this is why i would need to use shaving pine or bamboo to test the apex strength between apexes set on AlOx, SiC, and Diamond?

Wait a minute, I thought he effects of an abrasive not being able to cut vanadium were supposed to get worse the finer the AlOx abrasive used, and in particular were supposed to be most egregious when stropping high vanadium content steels using AlOx based stropping compounds on pliable substrates (at least according to this thread)?

If that were the case, shouldn't an s30v blade sharpened on a sintered ceramic aluminum oxide stone and then stropped using an aluminum oxide stropping compound on a hanging denim strop show very severe issues with this problem? Evidence that would be obvious and clearly visible in SEM photography (which is certainly more that 1000x more zoomed in than the USB microscope images I posted earlier)?
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You won't really have carbide blow out so much as carbide glazing.

Its the same phenomena you get when sharpening something like D2 or 440c on Arkansas stones. It might work but the outcome won't be as nice.
 
bluntcut said:
I referred to ~12um abrasive. At 3um there will be smoothing/polishing, i.e. weakened carbides (barely hang on) will be gone and divots get smoothened/erased. Still there will be carbides stand proud - per Todds pic, that carbide protruding from apex is not strong - especially from lateral force, agree?

Strop added at least 4 major variables: flex; lapping; wax; substrate fuzz... so complexity goes way up. It is a sure way to raise massive noise over signal - so speak.
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That is a small Buck Vantage in S30V - I have not measured the hardness myself. That particular sharpening was with a Chinese "edge-pro" knock-off ceramic stone (white sintered aluminum oxide), at 30 degrees. In the above image the round dark particles are the vanadium carbide.

I have sharpened this knife a variety of ways and NEVER observed even a single carbide being "pulled out" of the bevel face. In fact, I would argue that this image shows how well the carbides bind to the matrix.
 
Out on a limb ... I see edge quality might not be as good compare to diamond finished edge. Of course, diamond finished will has fractured/feathered apex but less than this one.

vSeHxg7.jpg


Todds - if you are willing (yeah and do us all a favor :thumbup:) to snap a few SEM images for 68rc 10V blade, I would send you a sample. Easier to see the different at a more extreme setting.

ToddS said:
That is a small Buck Vantage in S30V - I have not measured the hardness myself. That particular sharpening was with a Chinese "edge-pro" knock-off ceramic stone (white sintered aluminum oxide), at 30 degrees. In the above image the round dark particles are the vanadium carbide.

I have sharpened this knife a variety of ways and NEVER observed even a single carbide being "pulled out" of the bevel face. In fact, I would argue that this image shows how well the carbides bind to the matrix.
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didn't experience any catastrophic drop in sharpness after slicing several strips off some cardboard I have through the corrugations.
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Where I found a monstrous difference in two steel alloys, not sharpening media, was cutting hard rubber.

I would submit this cutting test for your perusal . . . find a chunk of thick, hard rubber . . . some kind of dock bumper or car bumper pad . . . wash it well to get all the dirt off . . . then take the freshly sharpened knives to it and cut some slivers off . . . doesn't have to be big hunks just kind of trim it up some. Mostly when I do this I am push cutting . . . when the edge goes I give the poor thing the benefit of the doubt and saw away but the end comes quick in any case. RIP

I found M390, properly heat treated (I know mine is because it cuts circles around any other steel I have) to blow S110V properly heat treated (I know because the maker told me so after checking it ((the maker of the knife not the maker of us))). Nary a diamond has violated the M390 . . . the latter has had the works.

For some reason the hard rubber is a true and palpable test . . . you can feel the edge peter out in several cuts or hang in there and feel like you are pealing an apple. There is no question when it goes.

YMMV : My 710 M390 seems not quite there but the Ritter M390 has set the standard that I use. I realize more than in the past edge geometry plays a good part but still.
 
ToddS said:
That is a small Buck Vantage in S30V - I have not measured the hardness myself. That particular sharpening was with a Chinese "edge-pro" knock-off ceramic stone (white sintered aluminum oxide), at 30 degrees. In the above image the round dark particles are the vanadium carbide.

I have sharpened this knife a variety of ways and NEVER observed even a single carbide being "pulled out" of the bevel face. In fact, I would argue that this image shows how well the carbides bind to the matrix.
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After participating in this thread (link below) I am 100%convinced of the fact, though stropping with anything will obscure the apex morphology fresh off the stone.
http://www.bladeforums.com/forums/s...90V-CTS204P-etc)/page2?highlight=stropping#31

I actually noticed some of the grittiness the eKretz described sharpening these steels on UF ceramic. Makes sense the carbides will survive in the swarf longer than the steel matrix.

Though by and large I believe the real negative effect is an inability to cleanly cut the carbides along the apex - per my reference to high Cr carbide steel on Arkansas stones.

Even in Todd's apex pic on page 5 the peak does not look to be as cleanly defined as other images he's done at that magnification.
 
Diamond stones.
Wow those are pretty different.
A nagura to use on diamond stones. Those particular type of stones obviously. That's a whole 'nother world.
 
Wowbagger said:
Diamond stones.
Wow those are pretty different.
A nagura to use on diamond stones. Those particular type of stones obviously. That's a whole 'nother world.
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Yes! I know that Heavyhanded has experience with a Diamond jointing stone a few years back (times flies!). I think the concentration was not that great and the binder was in question, overall slow abrasive but those Diamond-Waterston mentioned above may be indeed a 'nother world!
 
Diamond waterstones are pretty cool, they are not any faster but they sharpen anything. They have a much better feel than a regular diamond plate but still not as good as a regular waterstone. I tested out a Naniwa 1000 grit diamond waterstone once but I feel the higher grits would be of greater use.
 
6K stone (a 3mm thick layer of diamond in binder) was tempting a couple years ago but end up made my own test fixed diamond films. Meh on the 1K because most 1K waterstone (~15-20um abrasive) would adequately prepare the edge for higher grit finishes.

My diamond on thick clay paper backing didn't worked well, mostly due to low binding strength. Diamond embedded in epoxy worked very well once surface is full of protruding diamond (by: rub with high cv steels or thinned with fine sand paper).

Step function: When sharpen PM steels with carbide mostly in 2-5um, when abrasive cutting tip is inside the collision range (tip vs carbide) - results (end sum) are often poor because feed rate is too deep/high, so carbides on the surface are weakened by heavy impacts. So by experiences, ppl jump from ~12-15um to 1-3um diamond. 3um (maybe 75%) crossed over from collision/impact into shaping however with heavy pressure = higher feed rate = higher collision/impact. Aha, so 1um seems more safe doesn't it? Yes, if abrasive is fixed. No, with loose grit because lapping/tumbling/rolling 1um just mostly affect the matrix. Case of 6K diamond stone - edge trailing on mud (binder+diamond+swarf) help polishing, while edge lead will face fixed abrasive (plus minor mud plowing).

Ultimately when try to shape carbides on the apex (like teeth but many without gum in front and back of the tooth), we need avoid excessive sharpening force. sharpening force is mostly lateral and impart cantilevering/pry force at the tip of the carbide, compound with flex from thin matrix at apex = bye bye carbide if impact and or flex beyond yield. *note: flex will mostly be at carbide interface/boundary because carbide doesn't bend in these cases, which mean bending radius affectively near zero. Survived/shaped carbides useful for wear resistant when cutting/using forces involved are mostly compressive and some longitudal direction(ideally near zero lateral).

edit: forgot to mention - for shaping carbides on apex I use/recommend 0.25um diamond. guessing that cutting depth will be in ~30nm range, which should be low enough to keep carbide interface/boundary intact.

awestib said:
I don't know anything about the binder in those stones, how the apex property would be after edge leading vs edge trailing (muddy, non-muddy etc.) but this may be an option for high wear resistant steels. They are not inexpensive but renewable diamonds?:

https://www.japaneseknifeimports.com/collections/stones/products/diamond-1k-6k-stone-set

Any experience anybody?
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bluntcut said:
I get that, almost. So again, at least based on my experience and SEM pictures (for carbon steels that is) and your video, shape the bevel with SIC/DMTcoarse/SPSII and refine with 0.5-0.25 um on Balsa or even harder wood (I wonder though whether harder wood could potentially reduce the amount of "bond" of the diamonds on surface and more tumbling could occur).

I don't know how the edge/apex looks like after SIC or SPSII (I mean on a SEM scale) but I do know it seems to be pretty refined after DMT coarse (on carbon steel), so DMT coarse (light pressure) then 0.5 um on Balsa edge trailing should work well on VC steels?!

p.s. sorry, I don't know why the "reply with quote" looks so funky ...
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missing the close bracket ']' after [bluntcut 16663670

Steels with carbides in sub micron range don't have "step function" of very hard carbide with dia 2-5um. And for steels with mostly cementite, the collision is not applicable because abrasive will easily fracture/abrade these soft cementites (Fe3C).

In general, the coarser the grit, the far apart the abrasive cutting tips (sorry, for stating the obvious). So let pretend light pressure sharp DMT C on vc steels = normal pressure on low density DMT E, then strop with 0.5um on balsa. This combination should work fairly well, albeit apex will has some rounding (not talking about convex edge here) because any minute amount of depression in balsa will sprung up full strength at apex. Severity increase as edge thickness decrease until edge flex become to severe, thus produce wire edge.
 
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