Carbide Hardness Chart

[Deadboxhero]

I made a Carbide Hardness Chart for quick reference, useful for folks that are curious about which steels would be more wear resistant than others and what stones to use.

I thought it would be fun for folks that are really geeked out to be on the same page and also a fun thread to discuss Carbides in more detail than what we get in daily conversation.

It is very curious, especially to new folks how one type of steel like CPM S90v at 60hrc can be softer than 1095 at 65 HRC. Yet, CPM S90V will cut longer, especially in controlled slice cut testing on abrasive media.
The hardness and volume of different types of Carbides are a big deal.




For more advanced folks, I've listed the carbide unit cell chemistry and name all in one convenient place making it easier to read research papers and look up specific carbides





I advocate CBN/Diamond Waterstones, yet also I still use some alumina ceramic stones and this chart can be used for a decision making process of what to use for what.

Ceramic Abrasive "Alumina" Al2O3 2600Hv
Cubic Boron Nitride "CBN" 4500Hv

This is why I sharpen some steels with CBN to avoid fatigue at the Apex of the edge that is filled with tiny hard Carbides at great volume like Rex121, but I can use Alumina on ZDP-189 even if it's crazy high HRC and also has huge carbide volume because the Chromium Carbides are softer than the Alumina abrasive.


I omitted W2C, TiC because they are not commonly found in available knife steels, also W2C is only in Cemented Carbide Cobalt Metals.

I also excluded M2C because it's a secondary hardening carbide and I wanted to focus on the main, Undissolved carbides that contribute the most to wear resistance. This is also why I excluded Eta and Epsilon Transition Iron Carbides.

Extra Note ***Nitrides have slightly lower hardness than their equivalent Metallic Element bonded counterpart with the exception being Dichromium Nitride (Cr2N) and Chromium Nitride (CrN) being slightly harder than regular Chromium Carbides (Cr7C3)

[Sumdumguy]

So basically, Vanadium carbides are ALMOST as hard as my head?

Dang, that's impressive! :p

[JD Spydo]

So basically, Vanadium carbides are ALMOST as hard as my head?

Dang, that's impressive! :p

I've often wondered how some of these "carbides" would rank overall on the "Moh's Hardness Scale"? I do know one thing for certain any steel that is abundant in Vanadium Carbides can be a real monster to sharpen. One steel that immediately comes to mind is Crucibles notorious 440V ( S60V). I have even learned new curse words at times I've sharpened that steel.

I've also wondered at times with carbides like "tungsten carbide" for instance how it would stack up against diamond and other natural materials on the "Moh's Hardness Scale"?

[Larrin]

So basically, Vanadium carbides are ALMOST as hard as my head?

Dang, that's impressive! :p

I've often wondered how some of these "carbides" would rank overall on the "Moh's Hardness Scale"? I do know one thing for certain any steel that is abundant in Vanadium Carbides can be a real monster to sharpen. One steel that immediately comes to mind is Crucibles notorious 440V ( S60V). I have even learned new curse words at times I've sharpened that steel.

I've also wondered at times with carbides like "tungsten carbide" for instance how it would stack up against diamond and other natural materials on the "Moh's Hardness Scale"?

[Naperville]

Thank you BBB and Larrin!

[Cambertree]

Thanks Shawn and Larrin, this is excellent reference material. Thanks for taking the time to put it together, B.

Guys, have you ever written more in depth about eta carbide?

[Deadboxhero]

Thanks Shawn and Larrin, this is excellent reference material. Thanks for taking the time to put it together, B.

Guys, have you ever written more in depth about eta carbide?

Turned out to be a red herring.

It's covered here
https://knifesteelnerds.com/2018/04/23/ ... -of-steel/

Too small to do anything, just the intial iron carbides formed from carbon leaving the martensite during the start of the temper. As the Carbides grow, they coarsen to FeC3/MC3 with further time and temp during tempering.

Nothing to chase.

[Cambertree]

Thanks Shawn and Larrin, this is excellent reference material. Thanks for taking the time to put it together, B.

Guys, have you ever written more in depth about eta carbide?

Turned out to be a red herring.

It's covered here
https://knifesteelnerds.com/2018/04/23/ ... -of-steel/

Too small to do anything, just the intial iron carbides formed from carbon leaving the martensite during the start of the temper. As the Carbides grow, they coarsen to FeC3/MC3 with further time and temp during tempering.

Nothing to chase.

Thanks Shawn, I’ll check it out. I think I read that piece when it first came out, as I get Larrin’s Patreon feed, but it can sometimes take a couple of rereads for the learnings to soak in.

I was curious as I noticed when I made a couple of knives out of D2 with a long LN cryo soak, that it seemed to alter the harmonic quality of the steel.

The heat treated blanks would ring when struck with a very long, pure, sustained sound like a tuning fork.

I may be mistaken, but I think I read that steel tuning forks are actually deep cryo’d for this effect.

Jay Fisher comments on the phenomenon on his website:

https://www.jayfisher.com/Heat_Treating ... ess_Steels

I was curious as to what structural changes in the steel would produce this effect.

[Deadboxhero]

Thanks Shawn and Larrin, this is excellent reference material. Thanks for taking the time to put it together, B.

Guys, have you ever written more in depth about eta carbide?

Turned out to be a red herring.

It's covered here
https://knifesteelnerds.com/2018/04/23/ ... -of-steel/

Too small to do anything, just the intial iron carbides formed from carbon leaving the martensite during the start of the temper. As the Carbides grow, they coarsen to FeC3/MC3 with further time and temp during tempering.

Nothing to chase.

Thanks Shawn, I’ll check it out. I think I read that piece when it first came out, as I get Larrin’s Patreon feed, but it can sometimes take a couple of rereads for the learnings to soak in.

I was curious as I noticed when I made a couple of knives out of D2 with a long LN cryo soak, that it seemed to alter the harmonic quality of the steel.

The heat treated blanks would ring when struck with a very long, pure, sustained sound like a tuning fork.

I may be mistaken, but I think I read that steel tuning forks are actually deep cryo’d for this effect.

Jay Fisher comments on the phenomenon on his website:

https://www.jayfisher.com/Heat_Treating ... ess_Steels

I was curious as to what structural changes in the steel would produce this effect.

That's not how it works. Unfortunately the true facts aren't as sexy as reading about the mysterious tuning folks and aligning the Chakra of the steel. Which is too bad.

I wish it worked like that, how wonderfully simple that would make everything cause all I'd need to do is leave something alone in the dewar to cryogenically age.
However, nothing acutually precipates during cryo.
It finishes the quench which is a diffusionless process.

We get diffusion with heat. Diffusion of carbon from martensite into the iron makes iron carbides.

I left this LC200N in the liquid nitrogen cryo for a 100hrs.




ZERO improvement.


The key is sum of all parts not magic

[Cambertree]

That's not how it works. Unfortunately the true facts aren't as sexy as reading about the mysterious tuning folks and aligning the Chakra of the steel. Which is too bad.

I wish it worked like that, how wonderfully simple that would make everything cause all I'd need to do is leave something alone in the dewar to cryogenically age.
However, nothing acutually precipates during cryo.
It finishes the quench which is a diffusionless process.

We get diffusion with heat. Diffusion of carbon from martensite into the iron makes iron carbides.

I left this LC200N in the liquid nitrogen cryo for a 100hrs.




ZERO improvement.


The key is sum of all parts not magic

Thanks.

I read Larrin’s article and it answered my original question.

Just to be clear: I certainly wasn’t ascribing any pseudo-mystical or ‘magical’ properties to cryo’d steel. The seemingly different post heat treat auditory tone of the steel blanks was simply something I noticed when tapping in handle pins and randomly tapping the knife against metal jigs and fixtures, while working on it.

I had never heard of this before, so I googled a bit and was surprised to find both an experienced knifemaker commenting on it, and a large (and inconclusive) body of opinion on the effect of cryoing metal instruments.

https://www.straightdope.com/columns/re ... struments/

It’s possible I imagined it, or perhaps the different tone is related to the greater dimensional stability which can come with cryo quenching.

In any case, I don’t want to sidetrack further from the theme of your thread.

I was wondering, given your comments about alumina vs diamond abrasives, if you had any observations about any perceivable difference in fine edge quality between CBN and diamond finished apexes at similar grit levels?

It’s hard to quantify, but CBN emulsions seem to produce a ‘smoother’ feeling edge to me than diamond emulsions at the same grit rating on high carbide steels.

[GarageBoy]

Weird question - do the hardness of the carbides themselves vary with tempering temperature?

[Larrin]

Weird question - do the hardness of the carbides themselves vary with tempering temperature?

Not the primary carbides.