High vanadium/carbide tear-out questions

OhioApexing

OhioApexing

Sharpener
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it was only today that I discovered the issue of carbide tear-out when sharpening high-vanadium steels using non-diamond abrasives. Apparently, one can sharpen high-vanadium steels in this way but will tear-out the vanadium carbides, dramatically reducing the edge retention and leaving the apex prone to chipping. Because these steels are used primarily for the purpose of edge retention, carbide tear-out essentially nullifies their usefulness.
On to questions:
  • What percentage of vanadium qualifies a steel as "high vanadium?" I assume 3% - 4% wouldn't be considered as such. Obviously, S90V and S110V at 9% would. In short, at what percentage of vanadium should one be cautious about sharpening on ceramics?
 
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Once you get in the ultra fine range tear out isnt an issue any more. I use ultra fine ceramics to finish up before stropping.
 
For 'high vanadium' making a difference in sharpening in general, there seems to be a consensus that the relevant threshold for vanadium content is right around that 3% - 4% ballpark. In other words, it's more likely you'll notice shortcomings in your edge quality or edge retention if you're trying to sharpen with something other than diamond/cbn, when the vanadium content is up around 3% - 4% or higher. Think of a steel like S30V (4% vanadium) as an example where you'd probably start to notice issues, if you're trying to sharpen or refine your edge with aluminum oxide or maybe even silicon carbide at finer grit levels. Switch to refinement with diamond or cbn at that point and it'll be pretty obvious how much better it'll work to a crisper, more durable edge at a higher polish and much, much quicker and easier.

If you're wanting mirrored or high-polish edges on such steels, switch to diamond or cbn compounds on firm wood strops to make the jump beyond the EF/EEF diamond hones themselves. Going from DMT's EF (9 micron) or EEF (3 micron) hones, to 3-micron and finer diamond or cbn compound on a wood strop (basswood is popular) works very well to attain a mirror-polish on a steel like S30V.
 
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Todd S. argues that wear-resistant carbide tear-out is a rare event
https://www.bladeforums.com/threads/carbides-and-cutting-edges.1309485/

However, using anything but diamonds and CBN for honing the high-end knife steels, it is not possible to polish those wear resistant carbides sharp, as you'll only be abrading the steel matrix around them, burnishing it to the edge, and eventually getting a very sharp steel edge that won't last long. As you start cutting with such an edge, your ultra-sharp steel apex will quickly turn into a relatively dull edge made of big unpolished carbides.

Production DE razors have near 0.1 micron edge, a dull knife has over 1 micron edge, and as Todd commented his SEM images of a S30V knife edge, the unpolished vanadium carbides average 1-2 microns.

Todd Simpson's SEM image of S30V shows spheroidal vanadium carbides near the edge
s30v_06.jpg


...and an edge-on view of the same S30V edge:
s30v_edge_02.jpg

Todd's comment: "The vanadium carbides abrade more slowly than the surrounding matrix - that is basic principle of wear resistance.
You can see they sit a bit proud of the matrix."

The above edge was sharpened and stropped with aluminium oxide based abrasives.
If this edge was sharpened with diamonds or CBN, it would look very different, with smoother sides and sharper apex
 
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In my mind, high vanadium is > 4%. For those steels, I use diamonds or SiC almost exclusively depending on the finish I'm trying to achieve. Once in a while I will use the Spyderco UF stone after my finest DMT stone and prior to stropping. I don't have an electron microscope, but I find that it works quite well and refines the edge nicely. The UF seems like it very lightly polishes the edge on those more V-heavy steels, whereas the effect is more pronounced on something like, say, VG10.
 
>= 3% to be exact.
Please see our research comparing sharpening high vanadium knives using aluminium oxide versus CBN/diamond abrasives. This comparison has been done on knives with vanadium content of 1%, 2%, 3%, 4% and 10%.
http://knifegrinders.com.au/SET/Sharpening_High_Vanadium_Knives.pdf

But every research method has its limitations, and personally I use diamonds & CBN on blades with wear-resistant carbides contents at and over 1%.

But even people who have read our study on sharpening high vanadium knives keep mixing diamond and ceramic plates in sharpening them, getting a less stable edge than they could using diamonds only.

The important takeaway from alike studies is that when we sharpen a tool steel or high-end knife using anything but diamonds and CBN, it is not possible to polish those wear resistant carbides sharp, as we'll only be abrading the steel matrix around them, burnishing it to the edge, and eventually getting a very sharp steel edge that won't last long. As we start cutting with such an edge, the ultra-sharp steel apex will quickly turn into a relatively dull edge made of big unpolished carbides.
Production DE razors have near 0.1 micron edge, a dull knife has over 1 micron edge, and as Todd commented his SEM images of the S30V knife edge, the unpolished vanadium carbides average 1-2 microns in that CPM steel.
Yes, we can strop it back to razor sharp by burnishing the steel matrix over the edge and shaping it into a razor edge, but this edge will be short-lived without polishing the vanadium carbides which only diamonds and CBN can do.

Related reading:
Edge Retention in High-end Knives as tested by Nathan Stuart:
http://knifegrinders.com.au/Manuals/High-end_edge_retention.pdf

Knife Steel Nerds research by Larrin Thomas:
https://knifesteelnerds.com/2018/08/27/what-is-edge-stability
https://knifesteelnerds.com/2018/11/19/steel-edge-retention

Sharpening a wear-resistant knife is very different to a regular carbon steel, and requires a sequence of progressively finer diamonds/CBN, it is actually has more in common with sharpening ceramic knives than a carbon steel knife.

A common carbon steel knife we apex and deburr, and can get a lasting sharp edge even off a #150-300 abrasive.
A wear-resistant knife we apex, and then polish and polish and polish through a sequence of progressively finer grits diamonds/CBN; there is no way you can get a lasting sharp edge even off the #1000 - you need diamonds or CBN finer than that.
 
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The earlier description by Wootzblade (with pics from Todd S), of the S30V edge starting out ultra-sharp and then quickly degrading to an edge of 'big, unpolished carbides' perfectly fits my very first impression of S30V, when I tried to refine it with something less than diamond (I'd used AlOx stones, then tried stropping with green compound). I had noticed an initial hair-shaving sharpness which just completely evaporated after just a few cuts into a phone book, after which it wouldn't even cut the paper easily anymore. In my mind's eye, I was picturing an edge with a fragile, burr-like edge crumbling away into an edge that 'felt' (in the paper) like it'd gone suddenly rounded and blunt, after cutting the paper with it. In retrospect, I'm sure I was seeing the effects of the matrix steel burring, with little or no shaping or thinning of the carbides themselves. So, the burr collapses quickly, and what's left of the 'edge' reveals all the shortcomings of the materials used to sharpen it. That left an impression in my mind that has stuck to this day.

Contrast that experience to when I finally wised up and used diamond from start-to-finish (up to near-mirror, stropping with 3µ diamond on basswood), and suddenly my S30V edges were doing all the hair-popping tricks I expect of something like good 1095, and staying durable after some real-world cutting too. That also left a lasting impression in my mind. So, with steels like these, I don't even consider sharpening or maintaining them with anything but diamond anymore. It's a no-brainer for me.
 
Keep in mind, gentlemen, that there are often other carbides present as well, and not all of them are contained in as structurally sound a manner as others may be in the steel matrix. Tungsten comes to mind, and it is definitely present in some of the steels used these days. I know for a fact that this is a big problem with T15 because I've had it happen. And it was very visible under 240x magnification. Further, I could feel the carbides coming loose and rolling around under the blade on very fine hones. (I.E. Spyderco U.F.)

Edit to add: the above does NOT occur with diamond hones.
 
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I have a number of different knives that are S30V S110V M390 and M4 and ZDP-189,I also have a KME but since purchased 2 TSProf's because stone selection is lacking for the KME by far when compared to edge pro stone selection.

If I were you I would contact Jende Industries and get all 3 Spyderco Ceramic stones for the KME they are really hard stones and abrade everything fairly well,you may also look at getting some of the Venev Diamond stones from Gritomatic as they perform very well.

If you ever decide to get really serious into buying and maintaining a lot of high end knives then I would look at a TSProf Hapstone or EDGE Pro for better stone selection,the KME is still a really good system but they have done a major overhaul on it to improve anything and then add new gadget's that you can use along with it plus the rubber pads always come the KME Jaws and the do not hold anywhere near as good as the TSProf's clamp's.

Basedlarrydavid said:
First off, I'm brand new to knife sharpening but have been doing substantial reading/research for quite a while. For numerous reasons, I decided to go with the KME system. It comes with 140, 300, 600, and 1500 diamond hones and I picked up Chosera stones (aluminum oxide, I believe) running from a 1k to a 10k progression. My stropping progression begins at 1 micron using exclusively polycrystalline diamond emulsions and sprays.

At any rate, it was only today that I discovered the issue of carbide tear-out when sharpening high-vanadium steels using non-diamond abrasives. Apparently, one can sharpen high-vanadium steels in this way but will tear-out the vanadium carbides, dramatically reducing the edge retention and leaving the apex prone to chipping. Because these steels are used primarily for the purpose of edge retention, carbide tear-out essentially nullifies their usefulness.
On to questions:
  • What percentage of vanadium qualifies a steel as "high vanadium?" I assume 3% - 4% wouldn't be considered as such. Obviously, S90V and S110V at 9% would. In short, at what percentage of vanadium should one be cautious about sharpening on ceramics?
  • I can't really find diamond hones/plates for the KME past 1500 grit. If I don't hand sharpen, would I be at the mercy of a lengthy progression of diamond strops to get from 1500k down to 1 micron? AKA, does anyone know where I can pick up diamond plates/hones for the KME past 1500k?
Click to expand...
 
wade7575 said:
If I were you I would contact Jende Industries and get all 3 Spyderco Ceramic stones for the KME they are really hard stones and abrade everything fairly well
Click to expand...
This is what the discussion is about. The ceramic stones are not as hard as the Vanadium carbides. It would not be idea to use these from my understanding from all these threads on carbide tear out. I think they would be better than some stones for sure.

The kme does have a somewhat decent selection at gritomatic, but no where near the selection of edge pro style stones. In any case your right... Venev is likely the only diamond stones that have a larger grit selection than the standard kme diamond stones that go from 50grit to 1500. However the 2000 grit venev is like going backwards and should be avoided from what I've read. Continue with diamond or cbn strops instead I'd assume.
 
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Mo2 said:
This is what the discussion is about. The ceramic stones are not as hard as the Vanadium carbides. It would not be idea to use these from my understanding from all these threads on carbide tear out. I think they would be better than some stones for sure.

The kme does have a somewhat decent selection at gritomatic, but no where near the selection of edge pro style stones. In any case your right... Venev is likely the only diamond stones that have a larger grit selection than the standard kme diamond stones that go from 50grit to 1500. However the 2000 grit venev is like going backwards and should be avoided from what I've read. Continue with diamond or cbn strops instead I'd assume.
Click to expand...


The Venev stones are sold out everywhere. I already barked up that tree. I’m genuinely surprised that high-grit diamond stones aren’t readily available, considering the KME’s popularity.

I was considering a Hapstone, but the V7 was sold out everywhere, too. Plus, there are years worth of KME instructional videos out there. The good news is that my KME stones will fit the Hapstone should I make the switch later on.

Regarding the Spyderco ceramics, I was watching a Michael Christy video about this subject and he sharpened S110V finishing with the Spyderco stones before moving to strops. The difference in edge retention between the all-diamond route and the diamond/ceramic route was negligible at best. He seems to think that carbide tearout isn’t that big of an issue as long as you do the majority of your progression on diamonds.

After doing more research since this posting, it seems as though high-vanadium steels shine at lower (<5000) grits anyhow, with the carbides acting as extremely hard teeth.

That said, I still want 4”x1” diamonds, damnit. Lol.
 
wootzblade said:
Sharpening a wear-resistant knife is very different to a regular carbon steel, and requires a sequence of progressively finer diamonds/CBN, it is actually has more in common with sharpening ceramic knives than a carbon steel knife.

A common carbon steel knife we apex and deburr, and can get a lasting sharp edge even off a #150-300 abrasive.
A wear-resistant knife we apex, and then polish and polish and polish through a sequence of progressively finer grits diamonds/CBN; there is no way you can get a lasting sharp edge even off the #1000 - you need diamonds or CBN finer than that.
Click to expand...


Thanks for all of this info. As it stands now, I have an all-diamond hone progression from #100-1500, then an all-diamond stropping progression from 1um down.

What grit/micron steps would you recommend to fill the gap from #1500-1 micron? Aside from emulsions/sprays on strops, any KME aftermarket product recommendations?
 
Even Todd S. concluded that the vanadium carbides are not impacted until going to 3u (1500 grit). So, if you only sharpen to 300 or 600 grit it is a moot point. The main reason I'll use my 600 grit diamond plate is because it is good at removing the small final burr. Still, it doesn't touch the vanadium carbides. DM
 
David Martin said:
Even Todd S. concluded that the vanadium carbides are not impacted until going to 3u (1500 grit). So, if you only sharpen to 300 or 600 grit it is a moot point. The main reason I'll use my 600 grit diamond plate is because it is good at removing the small final burr. Still, it doesn't touch the vanadium carbides. DM
Click to expand...

Agreed, but as I said in the OP, I’m looking to make a sub-micron progression.
 
Basedlarrydavid said:
Thanks for all of this info. As it stands now, I have an all-diamond hone progression from #100-1500, then an all-diamond stropping progression from 1um down.

What grit/micron steps would you recommend to fill the gap from #1500-1 micron? Aside from emulsions/sprays on strops, any KME aftermarket product recommendations?
Click to expand...

We sharpen them with powered equipment, as detailed here https://www.australianbladeforums.c...37391-sharper-razors-sharpening-detailed.html

JENDE has a selection of nano-cloth hones with CBN and diamonds for KME https://jendeindustries.com/1x4-jende-nanocloth.html
Nathan, well-known in Australia sharpener of high-end knives uses them with his TsProf
https://www.youtube.com/channel/UCcfBINHsqEgFdpyuQ1x9QOA/videos

Summary of his tests on edge retention in high end knives is here:
http://knifegrinders.com.au/Manuals/High-end_edge_retention.pdf
 
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David Martin said:
Even Todd S. concluded that the vanadium carbides are not impacted until going to 3u (1500 grit). So, if you only sharpen to 300 or 600 grit it is a moot point. The main reason I'll use my 600 grit diamond plate is because it is good at removing the small final burr. Still, it doesn't touch the vanadium carbides. DM
Click to expand...

Sorry mate, but this is not what we are talking about. No problem bevelling wear-restiant high-vanadium blades with aluminium oxide, silicon carbide or ceramics; however the apexing (edge-setting) and honing should be done with abrasives harder than their carbides, practically it is CBN or diamond.

I have a chapter on high-end knives in my Knife Deburring book http://knifegrinders.com.au/Manuals/Knife_Deburring_book.pdf
It repeats what we discuss here; I've reread it today and can't think of any better wording
If you sharpen high-end knives, it is worth a look, agree or not.
 
The DMT EEF is rated 3 micron - 8,000 grit and would fill your gap nicely. Once the plate wears in it leaves a very fine finish but still cuts quick.

For us to know better what to recommend as far as your edge progression it would help to know what you are doing with the knives. Different tasks need different progressions if you want the longest lasting edges suited to the task at hand.
 
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