The Stoichiometry of Steel Carbides
Stoichiometry is the measurement and calculation of the ratios of different elements in a chemical reaction in relation to their mass. For information about the composition and properties of steel, please refer to the Knife Steel article. This article is largely about how to interpret the different formulae of alloy compositions in terms of the carbides they develop.
This may seem odd to those who either never studied chemistry, or have forgotten what they did study; after all, 1% Carbon by weight is 1% Carbon, right?
Sure, but 1% Carbon, 1% Chromium, and 1% Tungsten by weight are radically different; the individual atoms of different elements have different weights, and so a gram of Carbon represents many more actual Carbon atoms than a gram of Chromium represents Chromium atoms... and chemical compositions are defined by the number of atoms of each element, not their mass.
And that is the information we need: The atomic mass of each element (i.e. how much each atom weighs), the chemical formulae for the different types of carbides that can form, and the composition of the actual alloy in question.
Note 1: For the purposes of this discussion, the differences between carbides and nitrides are largely irrelevant. This is simply about how to interpret the chemical composition of a steel alloy.
Note 2: All values are rounded for convenience; chemical processes are almost never 100% efficient in terms of each element getting where it needs to go, and the actual behavior of complicated systems like steel alloys is often difficult to predict, even for experts in the field.
Atomic Weights
These are the AMU (Atomic Mass Unit) values for the relevant issues; this is a measure of how much a mol of atoms of that element weighs.
"Mol," is a number, like "dozen" (12), "score" (20), or, "gross" (144), but a "mol" is 6.022 x 1023. A dozen grains of sand will hardly be noticeable on your fingertip; a mol of grains of sand is about 17 trillion tons. Atoms are small; write that down.
The most basic atom is Hydrogen, with an AMU of 1.07, that is, a mol of Hydrogen atoms weighs 1.07 grams (it should be 1, since Hydrogen is just a proton and electron, but the isotopes Deuterium and Tritium increase the average mass because they have one or two neutrons).
Here are the relevant elements and their AMU values:
| Element | AMU |
| Carbon (C) | 12 |
| Nitrogen (N) | 14 |
| Vanadium (V) | 51 |
| Chromium (Cr) | 52 |
| Iron (Fe - Latin Ferrum) | 56 |
| Niobium (Nb) | 93 |
| Molybdenum (Mo) | 96 |
| Tungsten (W - German Wolfrahm) | 184 |
There are large differences at play, here. Alloy compositions are expressed for the benefit of the actual production of steel, not its analysis, use, or design; "How much of each element needs to go in to get the result I want?" That has to be expressed in mass, weight, because that's how it is measured out in production, even if it creates some inconvenience for those of us who wish to know what it all actually means.
As a result, a given mass of Vanadium represents almost twice as many atoms as the same mass of Molybdenum (hereafter shortened to, "Moly," for convenience), which would be about twice as many atoms as the same mass of Tungsten.
Carbides
Carbides are the hard pieces embedded in the (relatively) softer steel solution, and form as crystals from the various atoms. Importantly, carbide volume is based on the number of atoms involved, not the weight, and this is why the stoichiometric ratio is so important, as it represents the ratio of mass to number of atoms for a given carbide type.
The other major factor is carbide size (refinement); being hard but brittle, larger carbides are more prone to both breaking, themselves, and being pulled out of the steel solution. Smaller carbides are both tougher and leave more solution steel in between them for overall strength.
These are the chemical formulae (element with the number of atoms in each molecule in subscript), stoichiometric ratios, and approximate hardness values for most of the common carbides and nitrides formed in knife steels, along with the base allotropes (crystal formations) of the steel solution, for reference:
| Carbide | Stoichiometric Ratio | Hardness |
| FexC Austenite | - | 250V, 23Rc (Min) |
| FexC Martensite | - | 750V, 63Rc (Max) |
| Fe3C Iron Carbide (Cementite) | 14:1 | 950V, 68Rc |
| Cr23C6 Chromium Carbide (cubic) | 14:1 | 1000V, 69Rc |
| MoxC Molybdenum Carbide | 16:1 - 48:1 | 1300V -1900V |
| Cr7C3 Chromium Carbide (hexagonal) | 10:1 | 1400V |
| CrN/Cr2N Chromium Nitride | 3.7:1 / 7.4:1 | 1600V |
| CrV7C3 Chromium-Vanadium Carbide | 1.5:10:1 | 1800V |
| NbC Niobium Carbide | 8:1 | 2400V |
| WC Tungsten Carbide | 15:1 | 2600V |
| VC Vanadium Carbide | 4.25:1 | 2800V |
Let's use Chromium Carbide (hexagonal) as an example; it is both commonly desirable, both from being hard and giving other benefits, and easy to deal with mathematically, since the ratio is 10:1 (9.9:1, actually, but rounded to 10).
What this means is that those 7 Chromium atoms weigh 10 times as much as the 3 Carbon atoms; 1% Carbon by weight would ideally want to use 10% Chromium by weight. It doesn't, since it will always tend to form some of the carbides you don't want, if possible, but this tells you, for example, why D2 steel, with 12% Chromium and 1.5% Carbon, is not stainless; there's not enough Chromium left over from forming carbides to make the steel solution reasonably corrosion resistant.
Vanadium carbides are among the most desirable, for both being the hardest generally found in steels and having a very low stoichiometric ratio.
Moly carbides are misleading, since they usually form hybrid carbides with other elements, which are both varied and difficult to predict, and the stoichiometric ratio is very high.
Niobium carbides are interesting because they are both very hard, and form easily in most alloys, with a quite moderate stoichiometric ratio.
Nitrides are quite hard with a low stoichiometric ratio, and so have a powerful effect on wear resistance, but since Nitrogen is a gas, it is hard to get high fractions in an alloy.
You may notice that the hardness scale only uses Vickers for most carbides; this is because the Rockwell scale becomes misleading at higher values, with effective upper limits ranging from 65 to 80 (roughly 800 to 1800 Vickers) depending on the standard. I have chosen to stop at 69Rc, mostly for convenience of comparison to other sources of information.
Discussion of Selected Knife Steels
The following is an analysis of the composition of most commonly available knife steels, with recommendations below that I earn a small commission on, which is the only profit I receive from this project (there will never be any ads, and I will only ever accept sponsorships for items and brands that I fully believe in).
Please buy through the link if you were going to, anyway, so I can make a little money at no cost to you! And in either case, I hope you enjoy and appreciate the work.
Carbon Steels
1070 (0.7C)/1080/1084 (0.8C)/1095 (.95C): With no other carbide forming elements, these steels only ever form Cementite, placing an upper limit on their wear resistance and potential hardness, but they are durable and easy to sharpen, excellent qualities in survival knives.
ESEE 4: https://amzn.to/3R1KQuJ
5160 (0.6C 0.8Cr): The slight amount of Chromium is not enough to form significant carbides, so wear resistance is not improved, but the strengthening effect in the solution steel along with relatively low carbide volume makes this a very tough steel.
Buck Compadre 9.5" Wood Chopping Knife: https://amzn.to/3G9ti9L
52100 (1C 1.5Cr): Still not enough Chromium to form significant non-ferrous carbides, the carbide volume is significant. This steel combines good toughness and hardness.
Kramer Zwilling 8" Chef's Knife: https://amzn.to/40L2NkO
Tool Steels
O1 (0.9C 0.5Cr 0.5W): Still not enough alloying elements to significantly effect overall carbide hardness, this alloy hardens and tempers well.
L.T. Wright GNS Saber: https://amzn.to/46cCRQ0
A2 (1C 5Cr 2V 1Mo 0.3Ni): The 5% Chromium could theoretically use about a third of the Carbon to form Chromium carbides, but of course that never happens, but this is a fairly tough steel with decent carbide volume.
L.T. Wright Patriot: https://amzn.to/3R2nHZn
D2 (1.5C 12Cr 1V 1Mo): This alloy has pretty high carbide volume, a lot of which is Chromium carbide for solid wear resistance, it also hardens very well, if not being the toughest steel available.
Buck 263 Hiline Folding Cleaver 3.6": https://amzn.to/40JucUf
M4 (1.4C 4Cr 4V 5Mo 5.5W): Now we are getting complicated; that looks like a lot of alloy, and it does wind up with a good bit of VC, MoC, and WC, but it actually has a larger fraction of Iron carbides than D2; Molybdenum and Tungsten carbides have such high stoichiometric ratios, they don't contribute to carbide volume as much for the same mass, and also form in different temperature regimes.
Benchmade Freek 560: https://amzn.to/3G19q8K
3V (0.8C 8Cr 3V 1.3Mo): A little more straightforward, this is a modern steel, which is reflected in the better balance of Carbon to carbide-forming elements, resulting in a very tough steel with decent carbide volume, much of which is Chromium and Vanadium.
Cold Steel Master Tanto 6": https://amzn.to/47zCeBg
4V (1.35C 5Cr 4V 3Mo): Another modern steel, but less well balanced than 3V, with a more Iron carbide relative to its much higher carbide volume.
Kizer Feist Pocket Knife: https://amzn.to/40OwIbO
Cruwear (1.1C 8Cr 2.4V 1.6Mo 1.2W): A modern alloy, it gets a good bit of Chromium and Vanadium carbide with significant carbide volume, and still manages to score well in both toughness and hardness.
Spyderco Manix 2: https://amzn.to/3RclOcN
Stainless Steels
420 (0.15C 13Cr): The original stainless steel, it has extremely low carbide volume, but a lot of it is Chromium, so the wear resistance is actually better than many plain Carbon steels.
Old Hickory 417 Fillet Knife: https://amzn.to/47yswPt
420HC (0.5C 13Cr 0.3V 0.6Mo): The modern update of the classic, the increased carbide volume gives improved wear resistance, and while they are still mostly Chromium carbides, the Vanadium helps refine the carbide size for high toughness while the Moly helps retain corrosion resistance.
Buck 119 Bowie Knife 6": https://amzn.to/3R3fJiw
440A (0.7C 17Cr 0.75Mo): Another classic stainless steel, the moderate carbide volume contains a lot of Chromium.
Gerber Gear Scout Pocket Knife: https://amzn.to/3SQorlL
440C (1.1C 17Cr 0.75Mo): The last of the classic stainless steels still in common use for knives, this steel has a significant carbide volume, with quite a bit of Chromium carbide.
SOG Tellus FX: https://amzn.to/47hoMSy
154CM (1.05C 14Cr 0.4V 4Mo): Developed from 440C, this steel does not actually develop Moly carbides, leaving only Chromium and Iron carbides, but the significant carbide volume gives good wear resistance, while toughness and hardness are moderate.
Kizer Clairvoyant: https://amzn.to/49Es2sO
14C28N (0.62C 14Cr 0.1N): A modern Nitrogen steel, it forms hard nitrides in addition to Chromium and Iron carbides for decent wear resistance in a very tough alloy.
Kershaw Blur: https://amzn.to/3R0Br6T
8Cr13MoV (0.8C 13Cr 0.1V 0.15Mo): A modern Chinese alloy developed from 440A, with variations mostly involving the Carbon content, this is a decently tough steel with a moderate carbide content, only slightly refined by the Vanadium addition, it's most salient feature is its accessible price point.
CRKT LCK+: https://amzn.to/47jdmOe
LC200N (0.3C 1Mo 15Cr 0.5N): Another Nitrogen steel, this one biased towards extreme corrosion resistance, which it does well. The low carbide volume is enhanced with Chromium nitrides, but the overall volume is still fairly low, resulting in only moderate wear resistance, but high toughness.
Kizer Drop Bear: https://amzn.to/3MOVzGC
Nitro V (0.68C 13Cr 0.1V 0.11N): Another Nitrogen steel, this is a very balanced alloy. The moderate carbide volume and slight nitride addition result in a decently tough and hard steel with moderate edge retention.
Civivi Elementum II: https://amzn.to/3SE0zBE
VG10 (1C 15Cr 0.2V 1Mo 1.5Co): A common Japanese knife steel, it has a decent carbide volume with a lot of Chromium, and the Cobalt addition increases hardness for an excellent cutting edge.
Shun Sora 8" Chef's Knife: https://amzn.to/3SM5vEG
X50CrMoV15/1.4116 (0.55C 15Cr 0.2V 0.8Mo): An almost ubiquitous German knife steel, its moderate carbide volume includes enough Chromium for respectable edge retention, while its low hardness allows reasonably easy sharpening.
Wusthof 8" Chef's Knife: https://amzn.to/47hfK8k
S90V (2.3C 14Cr 9V 1Mo 0.4W): One of the earlier powder metal alloys, it stretches the definition of the word, "steel," by having more than 2% Carbon content, which should technically make it Cast Iron but for the sinter-forging process, and with a very high carbide volume (>20%), only the extremely high Vanadium fractions keeps the carbide size fine enough to not be unacceptably brittle. Only moderately hard, the wear resistance is of the highest order.
Spyderco Drunken Prestige: https://amzn.to/49xDdn8
S30V (1.45C 14Cr 4V 2Mo): A 21st century steel, this was one of the first alloys specifically designed for knives. A powder metal steel, the high carbide content is biased towards Vanadium carbides, although significant Chromium carbides are also formed, resulting in good wear resistance, although decidedly mediocre hardness and toughness.
Buck 112 Slim: https://amzn.to/3ukeToG
S35VN (1.4C 14Cr 3V 2Mo 0.5Nb): An evolution of S30V, the Niobium addition is rather small, but powerful, and helps make up for the slightly lower carbide content in terms of wear resistance, allowing improvements in hardness and toughness.
Buck 631 Paklite: https://amzn.to/3R6llJ6
S45VN (1.48C 16Cr 3V 2Mo 0.5N 0.5Nb): A further evolution of S35VN, this alloy adds Nitrogen to develop higher hardness at the cost of toughness from higher carbide/nitride volume.
Spyderco Para 3: https://amzn.to/3T2QSNt
Magnacut (1.15C 10.7Cr 4V 2Mo): The current king of the hill, this ultramodern powder-metal alloy was precisely engineered to balance toughness, hardness, and wear and corrosion resistance with precise alloy fractions for ideal carbide type, volume, and refinement. It brooks no equal in terms of overall performance; in any given attribute, you can find a superior alloy, but only at the cost of one or more other attributes, and to a greater degree.
MKM TKF Fixed Blade Outdoor Knife: https://amzn.to/3SE2ZjI
The Future
Magnacut was first released to the market in 2021; S45VN in 2019; S35VN, 2009; S30V, 2001. In absolute terms, Magnacut is about twice as strong as S30V, with similar wear resistance and superior corrosion resistance. In 20 years, the best knife steel available became twice as good.
What will we see in another 20 years? How much better will our materials become? What does that even mean?
Astute students of modern mythology, especially that surrounding knives and steel, may notice that my ratings and comments do not always line up with other available sources of information, despite my claims to have drawn from several of them, and wonder about the discrepancy.
The short answer is that I am approaching the question from the "opposite" side; most guides to knife steel are focused on the production side of the equation, i.e. "How do I balance the properties I want against the theoretical constraints that I know and think I understand," or even, "Which steel should I pick for a given task," which are perfectly valid approaches to the situation.
This project is about the end user; what are the actual, absolute properties of this item in relation to another variation, regardless of the theoretical considerations or ideal balance of properties for a given task. You have a knife; what do you need to know about it to use it safely and effectively for your current needs? We don't always get to choose, and the choices are not always straightforward.
The long answer will be an article of its own.
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