Carbide Hardness Chart

DeadboxHero · Jan 8, 2020

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)

Blues · Jan 8, 2020

That's great, Shawn. Thanks for sharing that with us. Makes things much clearer, imho.

DeadboxHero · Jan 8, 2020

I would have killed for this knowledge 5 years ago.

It was very confusing at first to sort all this out and there used to be constant arguments about amongst geeks, one example is molybdenum and tungsten carbides, etc and what was harder and what steel had what.

Well, if you plug in "Molybdenum carbide" into a Google search you don't actually get any information about what Carbides it makes inside of popular knife steels like 154cm.

So, I realize some folks will be glazed over by the unit cell crystal names but that is probably the most useful thing in this chart since you can Google search those and also it helps folks understand the research articles that talk about Carbides in steel.

That's the language that is used and what was missing in past discussions with folks trying to understand it.

Blues said:
That's great, Shawn. Thanks for sharing that with us. Makes things much clearer, imho.

Mr.Wizard · Jan 8, 2020

Thank you.

Here are a couple of abrasives references I found. Hopefully they are also helpful. Unfortunately I don't know the origin of the first, but the table is from Tribology of Abrasive Machining Processes.

tiguy7 · Jan 8, 2020

Great stuff, but 1 is Vickers and 1 is Knoop. Is there a fast and dirty way to get the steel inclusions and the abrasives on the same chart?

bucketstove · Jan 8, 2020

Hi
My estimates
https://imgur.com/a/mvhu4k9
https://knifesteelnerds.com/2018/11/19/steel-edge-retention/

Code:

+-10 points (1 px = 1000/121px = 8.2644628
Carbide or Abrasive                     HV0.05 microhardness vickers
Silica                                  504 -  909 HV0.05
Martensit                                595 - 1000 HV0.05
Fe3C                                    801 - 1198 HV0.05
Cr23C6                                  942 - 1404 HV0.05
Quartz                                 1000 - 1206 HV0.05
Fe2B                                   1000 - 1471 HV0.05
(W,MO,Fe)6C(In High Speel Steel)       1107 - 1644 HV0.05
Cr7C3 (12-20Cr)*                       1297 - 1702 HV0.05
(Cr,V)7 C3(20Cr,2-5V)*                 1495 - 2000 HV0.05
Alumina                                 1504 - 2000 HV0.05
CrN,Cr2N                               1578 - 1793 HV0.05
NbC (20Cr,5Nb)*                         2305 - 2818 HV0.05
WC                                     2404 - 2586 HV0.05
Silicon Carbide                         2404 - 2619 HV0.05
TiC                                     2404 - 2809 HV0.05
VC                                     2611 - 2991 HV0.05
W2C                                     2826 - 3206 HV0.05
*Alloying Content in the Steel (%)     

Diamond is 100HRC or 10,000 HV

Code:

+-10 points (1 px = 10 points, after scaling image so its 100px instead of 121px)

Silica                               520 -  900 HV0.05
Martensit                            580 - 1000 HV0.05
Fe3C                                 790 - 1210 HV0.05
Cr23C6                               930 - 1470 HV0.05
Quartz                              1000 - 1220 HV0.05
Fe2B                                1000 - 1480 HV0.05
(W,MO,Fe)6C(In High Speel Steel)    1120 - 1660 HV0.05
Cr7C3 (12-20Cr)*                    1290 - 1690 HV0.05
(Cr,V)7 C3(20Cr,2-5V)*              1500 - 2000 HV0.05
Alumina                             1500 - 2000 HV0.05
CrN,Cr2N                            1580 - 1800 HV0.05
NbC (20Cr,5Nb)*                     2310 - 2830 HV0.05
WC                                  2410 - 2620 HV0.05
Silicon Carbide                     2420 - 2640 HV0.05
TiC                                 2420 - 2840 HV0.05
VC                                  2620 - 3000 HV0.05
W2C                                 2840 - 3220 HV0.05
*Alloying Content in the Steel (%)

Diamond is 100HRC or 10,000 HV

This chart naturally doesn't mention
Microhardness anisotropy (harder on the corners)
arkansas-blue-black-stone.367724/#post-16584061
hardness-and-abrasion-capability.1478806/#post-17017412

Eli Chaps · Jan 9, 2020

Shawn (

DeadboxHero ),

Is there preferential carbide formation? Meaning, if a steel has a decent amount of say chromium and vanadium, will one carbide form more readily than the other? S90V has quite a bit of both but of course is known for it's vanadium carbide content. Maybe both types form but because the vanadium carbides are harder that "overrides" any discussion about chromium carbides?

samuraistuart · Jan 9, 2020

What happens when steel has chromium and vanadium like S90V is the chromium carbides become “enriched” by the vanadium. There will still be some pure vanadium carbide (VC), but a good % of the vanadium goes into the chromium carbide. This makes figuring out exactly what carbides are formed and in exact percentages a little weird to figure out. It’s not like you have chromium carbide and then vanadium carbides and they are purely separate from each other. This happens with other carbide formers too like Moly and Tungsten.

There are steels like 115w8 where you actually do have Tungsten carbides that are on their own, and very hard. There is very little chromium in 115w8. In M4, a good bit of the tungsten goes into the chromium carbides (and vanadium as well....a good bit goes into chromium carbides).

For me, the ideal (non stainless) knife blade steel is a simple very high carbon content and a good vanadium count that will reach ~67hrc. No chromium. No moly. Just carbon and vanadium. Something like Cru Forge V, but with much more carbon and much more vanadium (just enough chromium to help hardenability). 1.4%C, 4%V, 0.5%Mn, 0.5%Cr. Something like that anyway.

tiguy7 · Jan 9, 2020

bucketstove said:

Hi
My estimates
https://imgur.com/a/mvhu4k9
https://knifesteelnerds.com/2018/11/19/steel-edge-retention/

Code:

+-10 points (1 px = 1000/121px = 8.2644628
Carbide or Abrasive                     HV0.05 microhardness vickers
Silica                                  504 -  909 HV0.05
Martensit                                595 - 1000 HV0.05
Fe3C                                    801 - 1198 HV0.05
Cr23C6                                  942 - 1404 HV0.05
Quartz                                 1000 - 1206 HV0.05
Fe2B                                   1000 - 1471 HV0.05
(W,MO,Fe)6C(In High Speel Steel)       1107 - 1644 HV0.05
Cr7C3 (12-20Cr)*                       1297 - 1702 HV0.05
(Cr,V)7 C3(20Cr,2-5V)*                 1495 - 2000 HV0.05
Alumina                                 1504 - 2000 HV0.05
CrN,Cr2N                               1578 - 1793 HV0.05
NbC (20Cr,5Nb)*                         2305 - 2818 HV0.05
WC                                     2404 - 2586 HV0.05
Silicon Carbide                         2404 - 2619 HV0.05
TiC                                     2404 - 2809 HV0.05
VC                                     2611 - 2991 HV0.05
W2C                                     2826 - 3206 HV0.05
*Alloying Content in the Steel (%)    

Diamond is 100HRC or 10,000 HV

Code:

+-10 points (1 px = 10 points, after scaling image so its 100px instead of 121px)

Silica                               520 -  900 HV0.05
Martensit                            580 - 1000 HV0.05
Fe3C                                 790 - 1210 HV0.05
Cr23C6                               930 - 1470 HV0.05
Quartz                              1000 - 1220 HV0.05
Fe2B                                1000 - 1480 HV0.05
(W,MO,Fe)6C(In High Speel Steel)    1120 - 1660 HV0.05
Cr7C3 (12-20Cr)*                    1290 - 1690 HV0.05
(Cr,V)7 C3(20Cr,2-5V)*              1500 - 2000 HV0.05
Alumina                             1500 - 2000 HV0.05
CrN,Cr2N                            1580 - 1800 HV0.05
NbC (20Cr,5Nb)*                     2310 - 2830 HV0.05
WC                                  2410 - 2620 HV0.05
Silicon Carbide                     2420 - 2640 HV0.05
TiC                                 2420 - 2840 HV0.05
VC                                  2620 - 3000 HV0.05
W2C                                 2840 - 3220 HV0.05
*Alloying Content in the Steel (%)

Diamond is 100HRC or 10,000 HV

This chart naturally doesn't mention
Microhardness anisotropy (harder on the corners)
arkansas-blue-black-stone.367724/#post-16584061
hardness-and-abrasion-capability.1478806/#post-17017412

This helps! Thanks.

Eli Chaps · Jan 9, 2020

Thank you

samuraistuart

DeadboxHero · Jan 9, 2020

Chromium and Vanadium have a special relationship since Vanadium also like to fit inside the trigonal unit cells of the M7C3 chromium carbides and occupy the place of some of the chromium atoms. Vanadium is unique in that it forms stronger chemical bonds with Carbon thus enhances the M7C3 as CrV7C3.

So with S90V we get 13% Cr7C3 and 9% MC carbide volume in the matrix.
In M390 due to the large amount Cr we get 18% M7C3 (CrV7C3) and only 2.5% MC type volume

Yet steels like Vanax Superclean form no M7C3. Despite the high Cr due to the Nitriding process and nitrides/Carbides forming at lower temps.
13% MN type

Also a steel a low Cr steel like 2.2C,13Cr, 1Mo, 4V. Will also be dominated by Chromium Carbides

So there isn't a hard fast rule that more Cr will always make more Cr Carbides. Seems it's the balance of C,Cr,V amd the temps formed at when the steel is made from molten and cooled.

Another note I need to add here is carbide volume is Not to be confused by element %wt. Some folks don't understand and think that the element %wt is the carbide volume.

So how do we predicte the carbide volume than?

There isn't a way to predict the exact amount and type of carbide volume from just looking at the steel chemistry.
Folks can have good guesstimates but what's used is materials simulation software like Jmatpro and Thermocalc which is not available to the public. Even those are just estimates and have other considerations to account for.
One can use Energy Dispersive X-ray spectrography to identify the Carbides chemistry, manual point counting with a grind overlay on a Micrograph to add up volume total and xray diffraction to identify the specific unit cell types.

We have to remember that when we receive a bar of steel it's mostly Carbides in a soft matrix and we have to dissolve those Carbides to get the carbon we need to make the matrix hard. The remaining Undissolved Carbides are what's used to make the steel wear resistance in combination with the hard matrix that holds and supported them after HT.

Eli Chaps said:
Shawn ( DeadboxHero ),

Is there preferential carbide formation? Meaning, if a steel has a decent amount of say chromium and vanadium, will one carbide form more readily than the other? S90V has quite a bit of both but of course is known for it's vanadium carbide content. Maybe both types form but because the vanadium carbides are harder that "overrides" any discussion about chromium carbides?

Eli Chaps · Jan 9, 2020

Thanks Shawn.

I work in ultra-high purity metal but not steel. For us, carbides are typically a bad thing but given our processes and purities, we don't have a lot and those we do generate are extremely small.

Great discussion!

DeadboxHero · Jan 9, 2020

There are no Chromium Carbides in CPM M4
The tungsten goes into M6C

5.5% MC and 5% M6C volume

Here is a Micrograph of the Carbides with SEM. The MC type show darker, the M6C brighter. They use EDX/EDS to look at the chemistry of the Carbides.

Chromium presence does affect this but no chromium carbides are made.

For instance in Managense dominant air hardening steels we would have the Tungsten Carbides people desire over M6C but MN dominant steels aren't really made anymore since Chromium air hardening is superior for annealing and production.

There is a steel that is like a "Ultra" CruForge V called 1.2838
1.5C, 3.5V, 5Mn
Unfortunately the Carbides will be massive due to the Vanadium being a strong former and the temperture they form at when the steel is made and will have segregation when cooling. Would be sweet if it was a PM steel but who has the money to make it

I've been a huge fan of 1.2562.
Since it has 3% WC and 7.5% Fe3C and can rock 67-68rc.

samuraistuart said:
What happens when steel has chromium and vanadium like S90V is the chromium carbides become “enriched” by the vanadium. There will still be some pure vanadium carbide (VC), but a good % of the vanadium goes into the chromium carbide. This makes figuring out exactly what carbides are formed and in exact percentages a little weird to figure out. It’s not like you have chromium carbide and then vanadium carbides and they are purely separate from each other. This happens with other carbide formers too like Moly and Tungsten.

There are steels like 115w8 where you actually do have Tungsten carbides that are on their own, and very hard. There is very little chromium in 115w8. In M4, a good bit of the tungsten goes into the chromium carbides (and vanadium as well....a good bit goes into chromium carbides).

For me, the ideal (non stainless) knife blade steel is a simple very high carbon content and a good vanadium count that will reach ~67hrc. No chromium. No moly. Just carbon and vanadium. Something like Cru Forge V, but with much more carbon and much more vanadium (just enough chromium to help hardenability). 1.4%C, 4%V, 0.5%Mn, 0.5%Cr. Something like that anyway.

DeadboxHero · Jan 9, 2020

Eli Chaps said:
Thanks Shawn.

I work in ultra-high purity metal but not steel. For us, carbides are typically a bad thing but given our processes and purities, we don't have a lot and those we do generate are extremely small.

Great discussion!

Thanks, yeah give this article another read, it's one of my favorite works Larrin has done. He really gets into the complexity of things and can enhance the discussion.
https://knifesteelnerds.com/2019/07/15/carbide-types-in-knife-steels/

DeadboxHero · Jan 9, 2020

Eli Chaps

Here is another fun curiosity for you on the subject of Carbide types formed.

There aren't any Molybdenum carbides formed in ats-34, rwl-34, 154cm, cpm154
Unless using a high temper to make Mo2C tempering Carbides for secondary hardening at consequence to reduced Strength.

So, just Mo rich M7C3.
Again, some folks confuse the 4% Molybdenum element wt in this steel with actual carbide volume.

Just 17.5% Mo rich M7C3 volume is made.

wade7575 · Jan 9, 2020

Eli Chaps said:
Shawn ( DeadboxHero ),

Is there preferential carbide formation? Meaning, if a steel has a decent amount of say chromium and vanadium, will one carbide form more readily than the other? S90V has quite a bit of both but of course is known for it's vanadium carbide content. Maybe both types form but because the vanadium carbides are harder that "overrides" any discussion about chromium carbides?

I was reading an article the other week and forget where I seen it but I think you would have enjoyed it,I forget the exact steel it was about but I think it was S110v and the how carbide's are formed.

From what I recall it said that chromium inhibit's vanadium's ability to form carbides so they use a double crucible method where they melt the vanadium in a separate crucible in top of the other one where it form's vanadium carbides first then it's sprayed into the lower crucible at the end of the process.

tiguy7 · Jan 9, 2020

DeadboxHero said:
There are no Chromium Carbides in CPM M4
The tungsten goes into M6C

5.5% MC and 5% M6C volume

Here is a Micrograph of the Carbides with SEM. The MC type show darker, the M6C brighter. They use EDX/EDS to look at the chemistry of the Carbides.

Chromium presence does affect this but no chromium carbides are made.

For instance in Managense dominant air hardening steels we would have the Tungsten Carbides people desire over M6C but MN dominant steels aren't really made anymore since Chromium air hardening is superior for annealing and production.

There is a steel that is like a "Ultra" CruForge V called 1.2838
1.5C, 3.5V, 5Mn
Unfortunately the Carbides will be massive due to the Vanadium being a strong former and the temperture they form at when the steel is made and will have segregation when cooling. Would be sweet if it was a PM steel but who has the money to make it

I've been a huge fan of 1.2562.
Since it has 3% WC and 7.5% Fe3C and can rock 67-68rc.

Great show and tell. Love the visual aids.

DeadboxHero · Jan 10, 2020

Wade, it's all melted together.

It's the balance/amounts of C,Cr,V %wt element volume and the tempertures the Carbides form at and cooling rate from molten to solid that determines size and the amount of M7C3, M23C6 and MC type formed. Not what you described.

Here is a fun video of the PM process used for making high Carbide volume steels.

wade7575 said:
I was reading an article the other week and forget where I seen it but I think you would have enjoyed it,I forget the exact steel it was about but I think it was S110v and the how carbide's are formed.

From what I recall it said that chromium inhibit's vanadium's ability to form carbides so they use a double crucible method where they melt the vanadium in a separate crucible in top of the other one where it form's vanadium carbides first then it's sprayed into the lower crucible at the end of the process.

wade7575 · Jan 10, 2020

If I can find the article I read I will link it here,I just know they said that chromium inhibit's vanadium carbide formation and that they used a double crucible,I can not say if it's done that way all the time but that's the way it was described in the article I read.

Eli Chaps · Jan 10, 2020

wade7575 said:
I was reading an article the other week and forget where I seen it but I think you would have enjoyed it,I forget the exact steel it was about but I think it was S110v and the how carbide's are formed.

From what I recall it said that chromium inhibit's vanadium's ability to form carbides so they use a double crucible method where they melt the vanadium in a separate crucible in top of the other one where it form's vanadium carbides first then it's sprayed into the lower crucible at the end of the process.

As an old metal caster I'm having a hard time picturing a setup like that and how it would work. If you find the article, please do share.

Carbide Hardness Chart

hovering overhead