Carbide Volume Fractions in Tool and Knife Steels
How much carbide and nitride each of 38 tool and knife steel grades carries after a typical heat treatment, split by the type of particle that forms it. A reference summary of published practice and not an Aobo Steel specification.
What carbide volume measures
Hard carbide and nitride particles are what a tool steel cuts with. The volume of them in the steel is the single number that sits closest to wear resistance on a data sheet, and a grade with a high volume of them will hold an edge, a die edge or a wear surface for longer under abrasion. The same particles are brittle and they take carbon and alloy out of the matrix around them, so a high carbide volume is paid for in toughness, and the trade between the two is what this table is read for.
Volume is set by chemistry and by the hardening temperature together, so it cannot be read off the carbon content. A steel carrying 12 per cent chromium forms more than twice the carbide volume of a low alloy grade at the same carbon, because chromium carbide draws chromium, iron and other carbide formers out of solution with it. Raising the austenitizing temperature dissolves part of what is there and lowers the volume that survives to room temperature.
Carbide volume of 38 tool and knife steels
Carbide and nitride volume fractions by particle type
| Steel | Fe3C | CrC | CrVC | MC | M6C | MN | CrN |
|---|---|---|---|---|---|---|---|
| CPM M4 | – | – | – | 6.5 | 7 | – | – |
| M2 | – | – | – | 2 | 10.5 | – | – |
| 410 | – | 3 | – | – | – | – | – |
| 420 | – | 3 | – | – | – | – | – |
| AEB-L | – | 6 | – | – | – | – | – |
| Sleipner | – | 8 | – | – | – | – | – |
| 440A | – | 10 | – | – | – | – | – |
| 440C | – | 12 | – | – | – | – | – |
| D2 | – | 15.5 | – | – | – | – | – |
| 154CM | – | 17.5 | – | – | – | – | – |
| ZDP-189 | – | 36 | – | – | – | – | – |
| CruWear | – | – | 5.9 | 3.4 | – | – | – |
| S35VN | – | – | 10.5 | 2.5 | – | – | – |
| S30V | – | – | 10.5 | 4 | – | – | – |
| S90V | – | – | 13 | 9 | – | – | – |
| S125V | – | – | 16 | 12.5 | – | – | – |
| BG-42 | – | – | 16 | – | – | – | – |
| Elmax | – | – | 16 | 2 | – | – | – |
| M390 | – | – | 17.5 | 2.5 | – | – | – |
| S60V | – | – | 21.5 | 2.1 | – | – | – |
| Vanax | – | – | – | – | – | 4 | 10 |
| LC200N | – | – | – | – | – | – | 4.5 |
| 3V | – | – | – | 5.1 | – | – | – |
| Vanadis 4E | – | – | – | 8.2 | – | – | – |
| N690 | – | 18 | – | – | – | – | – |
| Rex 45 | – | – | – | 2.5 | 5.3 | – | – |
| 5160 | 0 | – | – | – | – | – | – |
| 1095 | 3 | – | – | – | – | – | – |
| O1 | 3 | – | – | – | – | – | – |
| O2 | 3 | – | – | – | – | – | – |
| 52100 | 6 | – | – | – | – | – | – |
| 26C3 | 8 | – | – | – | – | – | – |
| A2 | – | 6 | – | – | – | – | – |
| 19C27 | – | 8 | – | – | – | – | – |
| Niolox | – | 8 | – | 1 | – | – | – |
| XHP | – | 22 | – | – | – | – | – |
| Vanadis 8 | – | – | – | 15 | – | – | – |
| 10V | – | – | – | 17.5 | – | – | – |
Source, carbide volume fractions for different knife steels, Table 8.2 on printed page 84 of the source, which is PDF page 91 of the copy consulted.
Volumes are per cent of the steel by volume for a typical heat treatment and they shift with the austenitizing temperature. A dash is a cell the source leaves empty, which means none of that particle type is present, and the source prints an explicit zero for the iron carbide in 5160. A reference table only, it is not an Aobo Steel specification.
How to read the table
The seven data columns give the volume of each particle type in per cent. Fe3C is iron carbide, the softest of the group and the one a plain carbon or low alloy steel runs on. CrC is chromium carbide, which carries the stainless and high chromium tool steels. CrVC is a chromium vanadium carbide and MC is a vanadium rich carbide of the kind the powder metallurgy grades form. M6C is a molybdenum and tungsten carbide and it is the one the high speed steels run on. MN is a metal nitride and CrN is chromium nitride, and the two appear together only in the high nitrogen stainless grades.
A dash marks a cell the source leaves empty, which means that particle type is not present in the steel, and the source prints an explicit zero for the iron carbide in 5160. Reading a dash as a missing measurement would be wrong here, since most grades carry one or two particle types and leave the rest empty.
The spread across the table is wide. The carbon and low alloy grades sit between 0 and 8 per cent iron carbide, the chromium carbide grades run from 3 per cent in 410 and 420 up to 36 per cent in ZDP-189, and the powder metallurgy stainless grades carry 5.9 to 21.5 per cent chromium vanadium carbide with as much as 12.5 per cent vanadium carbide beside it. The two high nitrogen grades carry nitrides, Vanax at 4 per cent metal nitride and 10 per cent chromium nitride, and LC200N at 4.5 per cent chromium nitride.
Particle size is a separate variable from volume. A powder metallurgy grade and an ingot grade of the same chemistry carry the same volume, and the powder route delivers it in smaller and more evenly distributed particles, which shows up in toughness and grindability rather than in wear resistance. Two grades in the table, 154CM and CPM-154, have identical composition and differ only in how the carbide is delivered, and the source reports no measurable difference between them in edge retention testing.
Related reference data
The hardness of each of these particle types is on the tool steel carbide types page, measured abrasive wear data is on the abrasive wear test data page, and grades selected for wear resistance are on the abrasive wear resistant tool steels page. The knife grades in the table and how they are chosen are covered on the knife steel types page. A property comparison across the tool steel groups is on the tool steel properties chart, and the stainless side of the same question is on the martensitic stainless steel properties chart.
Reference data compiled from Knife Engineering, Steel, Heat Treating, and Geometry (Larrin Thomas). Table 8.2 is printed on page 84 of the printed book, which is PDF page 91 of the copy consulted. The values were read from the page image rather than from an automatic text layer.