Vanadium Carbide sharpening stone

BluntCut MetalWorks

BluntCut MetalWorks

Knifemaker / Craftsman / Service Provider
Joined
Apr 28, 2012
Messages
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I've been looking for fixed abrasives stone with sub-micron grit. Enter CPM S-90V, it has 9% of vanadium and also stainless. Since Vanadium carbides are quite hard, hence could be a tweener between diamond and alox/sic/ceramic. btw - this type of stone will supports edge-lead stroke :D

Stone1: Annealed, ~ 24hrc, uniform Vc distribution, uniform grain.
It worked reasonably well for sub-micron edge. I was able restored shaving-edge for: opinel, mora, endura (vg-10), d2 and s30v. There was abrasion occured under magnication but it abrades very slowly.

Stone2: Quenched - well my little torch failed to achieve austenitize temp 1150c for a crude quench, so will wait for a bigger torch on its way.
I expect quacky grain growth and possibly crack from bad quench process, just hope to achieve >67rc martensized. May be this stone will abrade & burnish at the same time.

Your thoughts/ideas/laughs...
 
to clarify, you took a piece of cpm s90v to use as a sharpening stone ?

not sure the carbides are there yet on the annealed state, dont they need a correct heat treatment to form?

anyway, i assume you'll have to abrade the steel matrix to have them showing on the surface too.
 
pwet said:
to clarify, you took a piece of cpm s90v to use as a sharpening stone ?
Click to expand...
Yes.

not sure the carbides are there yet on the annealed state, dont they need a correct heat treatment to form?
Click to expand...
"CPM steels are HIP consolidated from tiny powder particles, each having uniform composition and a uniform distribution of fine carbides. Because there is no alloy segregation in the powder particles themselves, there is no alloy segregation in the resultant compact. The uniform distribution of fine carbides also prevents grain growth, so that the resultant microstructure is fine grained."
http://www.crucibleservice.com/eselector/general/generalpart3.html

Even in annealed state, my 1x30 belt has hard time with it, hardly any sparks using 80 grit belt.

anyway, i assume you'll have to abrade the steel matrix to have them showing on the surface too.
Click to expand...
Yes. First I used belt-sander to flatten, then diamond plate to get more flat and desirable scratch pattern. Once the surface VC is worn out, I use diamond to abrade/lap a thin layer to expose new carbides. A renewable abrasives, similar to a ceramic stone, while diamond plate is non-renewable.
 
bluntcut said:
"CPM steels are HIP consolidated from tiny powder particles, each having uniform composition and a uniform distribution of fine carbides. Because there is no alloy segregation in the powder particles themselves, there is no alloy segregation in the resultant compact. The uniform distribution of fine carbides also prevents grain growth, so that the resultant microstructure is fine grained."
http://www.crucibleservice.com/eselector/general/generalpart3.html
Click to expand...

doesnt say anywhere that the carbides are there at the annealed state, there is carbon, chromium, vanadium etc but the carbide forms when you heat treat by combining with the carbon .... similar to stainless getting stainless only once het treated ...

at least thats my understanding, i couldbe wrong as i'm not a metalurgist by any stretch.
 
I'm not a metallurgist either. But I do see 'carbides', 'alloy', 'segregation' the main reasons (ok, plus elements purity) for PM. In this PM case, additional CrC form (depend on HT process) during austenize to matensinitic (iron -> steel) state. Also if without carbides at annealed state, my belt would wears at the same rate as grinding an iron bar. My worn belts disagreed ;)
 
Before final heat treat of a blade, carbides are already formed from the molten metals, and stainless steel is already stainless. Changes to properties/carbide fraction happen in heat treat, but the initial melt, pour, pressing, and rolling are all part of heat treating/forging as well.
 
I quenched the annealed s90v stone using the jet-engine sounding propane torch. Sadly it warped (bowl, x y directions). After 15 minutes with diamond plate, I figured it would take me another 2 hrs before I've a flat surface again. So, hey maybe I can gently hammer it flat :barf: Well, I now have a 2" stone. Spent another 15 minutes flatten it, good enough to for testing...

Used stone flat surface: I got same results as annealed stone.

Used stone edge (a burnisher?):
a) carbon knives (opinel, mora, box-cutter, old-hickory - dmt F finished): All were able to push cut phonebook paper at 45*.

b) vg-10, s30v (dmt ee finished): after a few minutes on s90v stone edge, both knives seem slice & pushcut phonebook paper more quietly.

Conclusion: S90V is NOT worthy of being a stand alone stone but handy to know in a pinch, you can use the spine edge of high VC knives to touch up lower or no alloy knives.
 
It sounds like it would make a good honing steel though. And i wonder how one of those cera-titan type metals would work for this application. Just food for though since i'm not getting my hands on any of this stuff anytime in the near future :P thanks for sharing the experiment
 
Another thought, check out how lapping is done if you want to play with a metal "sharpening stone". A piece of lapped-dead-flat cast iron doped with diamond compound or CBN / Boron Carbide might be just what you're looking for.
 
Komitadjie said:
Another thought, check out how lapping is done if you want to play with a metal "sharpening stone". A piece of lapped-dead-flat cast iron doped with diamond compound or CBN / Boron Carbide might be just what you're looking for.
Click to expand...

Lapping wise - I hasn't tried lapping on cbn/diamond charged cast iron yet. I did tried: glass, ceramic, various stainless, wood, clay, paper, plastic, brick, etc... For high hardness (non-embedable) surfaces, diamond & cbn tore/wore them up. Also these surfaces are not renewable (except more spray/smear of diamond), plus non-fixed abrasives are not conducive to edge-leading stroke.

If S90V( or fancy me a 15V) would acts like a super-fine file (sharp abrasives embeded throught out in quenched metal), we would have a cool sharpening stone with grits go below 3um & sub-micron. Also we all know the limitations of diamond plate & film.

I think, I understand why you recommended cast-iron (cementited matrix) :) maybe someday, I would try to cementite s90v by adding a bunch of carbon when during austenite (definitely I need a bar thicker than 0.11").
 
I've never tried SHARPENING on a lap myself, just more conventional uses. I have done a fair bit of surface finishing on a cast-iron lap, though, mostly for seal surfaces that can't use gaskets and have to rely on perfection of surface finish for their seal. It seems like with a softer material like gray cast iron (most commercial laps) you would end up with an edge-trailing stroke anyway, to avoid potential of catching the edge, and "plowing" abrasive in front of it.

If you can avoid the carbides pulling out, I'd think it could work... Micrography of the etched surface could be very interesting to see.
 
After a loud 'DOH!'.

I used waterstone to create carbide haze surface - i.e. where waterstone abrasive (alumina=alox) abraded the steel matrix, leaving carbides partially sticking out of the surface. It calls 'haze' because the surface will never goes mirror because the polishing agent is softer than some elements in the target material.

a) DMT E => 800 grit haze => s90v stone cuts and finished like 5 to 2microns.
b) DMT EE => 4K haze => s90v stone is between 1.5 to 0.5 micron.

a&b abrade carbon & vg-10 at about 1/3 speed of diamond/cbn and definitely faster than waterstone. note: comparison based on per centimeter-square. Stone still cuts as *new* after 3 knives, could suggest decent surface abrasives durability. After all, we count on the WC for wear resistant.

I'll make a new longer stone, hopefully my jet-engine torch generates enough heat.

Thoughts/comments are appreciated...
 
I've been reading this with interest. I have used the spine of a knife occasionally like a 'steel', more often for removing burrs or to realign an edge on some simpler blades.

This thread had me picking up my Spyderco Manix2 in S90V. Nice thing about a blade like this, the wide and very nearly dead-flat grind makes a pretty sizeable hone (as broad as many pocket hones). I have a cheap little wood-handled paring knife (Japan), with what seems to be some pretty coarse-grained stainless 'mystery steel'. I use it almost daily, for slicing fruit or whatever. But it also serves as a cheap test subject for trying out different hones/stones or stropping abrasives. I 'honed' the edge of this knife on the side of the Spyderco's S90V blade, and actually raised a fine burr with it (using a circular/elliptical motion, much as I do with my pocket hones). I think the grind lines on the factory-finished Spyderco blade might actually enhance the honing a bit. Maybe needs a little more 'research', but I can see some potential value in this... :)


David
 
Sure, if we put a mirror finish on this 67+ hrc s90v stone, it could be use as a sharpening steel. A better steel can be made by hammer the annealed s90v around a rod to make a lengtht wise arch before quench it. btw - arch stone shape would be strong, i.e. probably won't shatter if drop onto concrete from 3 meters height.
 
Obsessed with Edges said:
I've been reading this with interest. I have used the spine of a knife occasionally like a 'steel', more often for removing burrs or to realign an edge on some simpler blades.

This thread had me picking up my Spyderco Manix2 in S90V. Nice thing about a blade like this, the wide and very nearly dead-flat grind makes a pretty sizeable hone (as broad as many pocket hones). I have a cheap little wood-handled paring knife (Japan), with what seems to be some pretty coarse-grained stainless 'mystery steel'. I use it almost daily, for slicing fruit or whatever. But it also serves as a cheap test subject for trying out different hones/stones or stropping abrasives. I 'honed' the edge of this knife on the side of the Spyderco's S90V blade, and actually raised a fine burr with it (using a circular/elliptical motion, much as I do with my pocket hones). I think the grind lines on the factory-finished Spyderco blade might actually enhance the honing a bit. Maybe needs a little more 'research', but I can see some potential value in this... :)


David
Click to expand...

Idea of using s90v came up while back when I sharpened a few knives on my Gayle Bradley cpm-m4 blade (4% VC, 5% WC). Since WC is softer than VC, therefore I picked s90v to test. Plus s90v is stainless so I don't have to worry about rust or oxidation from swarf.

I found grind lines from diamond plates(XX, X, C, F, E) didn't help with super slow cutting speed. So by exposing carbides 'haze' (a.k.a carbide shadow, therefore no mirror look), it cuts many times faster.

Hopefully someone replicate this experiment by using any high % Vanadium alloy steels (s90v, 9v, 10v, 15v, s110v) tempered or quenched state.
 
Here is 1x2" broken piece of the s90v stone

s90vhaze20130123.jpg


The shiny part is dmt E lapped.
 
After using the stone for a few days, it worked well as a finishing stone. And it resonates definitive sounds when an edge has burr or wire edge - metal against metal effect. however too much trouble for hit & miss benefits with this stone, I won't pursue this any further unless new ideas comeup/inject into this thread.

Well, I decide to make a s90v fixed blade - comedic results.



The blade is very sharp and tough - it survived 45 minutes of brutal batoning session. Obviously the handle is not tough - lol didn't blow torch to soften it enough and had many holes. I cut myself while trying to fit the broken blade into the wood scale - the knife pivoted on the vise into fingers. :D my quick & hurry *bone head* moment.
 
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