Tungsten carbide hardness: how hard it is, and why it varies
Tungsten carbide hardness is a range, not one number: cobalt content and grain size mostly set it, and every figure belongs to one test method and load. Below are each source's figures, and what they mean for a worn tool you might sell.
How hard is tungsten carbide?
Cemented carbide grades span about 800 to 2800 on the Vickers scale at a 10 kgf load (HV10), according to ITIA. Cemented carbide means tungsten carbide (WC) grains held in a metal binder, usually cobalt. ITIA puts the tough end beside high-strength steels and the hard end beside hard ceramics.
A 2024 review gives typical WC-Co values of about 700 to 2200 HV30, higher for binderless and nano-grained grades; NTP gives 1250 to 1900 Vickers as typical, citing Brookes (1998).
Tungsten carbide with no binder has its own figures, and they differ by source. A 2022 paper gives WC itself 1800 to 2000 kgf/mm², on a par with alumina and silicon carbide; a commercial binderless material in another 2022 study is listed at 2800 HV. They are different materials and tests, so neither is the one true figure.
Sources: ITIA: Cemented carbides, a success story (newsletter, June 2010); Eclética Química 49 (2024): review of cemented carbide properties and tests; NTP Report on Carcinogens, 13th edition: cobalt-tungsten carbide profile; OSTI 1981641: WC-Co grades and grain size (2022); OSTI 1922808: WC-Co and binderless WC materials (2022).
What makes one grade harder than another
Grain size and binder content do most of the work: finer WC grains and less cobalt give a harder grade, coarser grains and more cobalt a tougher one. Grain size is the size of the WC crystals after sintering, the furnace step that turns pressed powder into a dense part. Tungsten carbide grades covers both settings in detail.
In ITIA's examples a 6% cobalt grade measures 1450 HV10 and a 20% cobalt grade 800 HV10, a drop of 650 points. At a fixed 12 wt% cobalt, a submicron grade measures 1450 HV10 and an extra-coarse grade 1070 HV10, so grain size alone is worth 380 points.
Nickel in place of cobalt tends toward higher toughness and lower hardness, iron toward the reverse, per the 2024 review.
NTP's table of representative machining grades (from Brookes 1998; NTP calls the ISO codes guidance only) runs P grades from 1900 down to 1250 HV, M grades from 1590 to 1380 HV, and K grades from 1850 HV at K01 to 1320 HV at K40. In each group, hardness falls as the number rises.
Sources: OSTI 1981641: WC-Co grades and grain size (2022); NTP RoC background document on hard metals (2010); ITIA: Cemented carbides, a success story (newsletter, June 2010); Eclética Química 49 (2024): review of cemented carbide properties and tests.
Tungsten carbide Mohs hardness
NTP puts tungsten carbide at "approximately 9 on the Mohs scale, slightly less hard than diamond", and gives cobalt a 5. NTP takes the figure from a 1996 reference.
USGS (2021 Minerals Yearbook) calls carbide almost as hard as diamond, and ITIA's home page says close to diamond; both are plain-language descriptions, not measurements.
A single Mohs figure for tungsten carbide says nothing about the gap between ITIA's 800 HV10 grade and its 1450 HV10 grade. Grades are rated in Vickers or Rockwell A instead.
Sources: NTP RoC background document on hard metals (2010); USGS Minerals Yearbook 2021: Tungsten; ITIA home page; ITIA: Cemented carbides, a success story (newsletter, June 2010).
How hardness is measured on cemented carbide
Vickers is the standard number: NTP defines it as resistance to indentation by a diamond penetrator of special profile. A 2022 paper calls it typical for hard metals (Knoop is more common for ceramics), and the 2024 review names HV30, a 30 kg load, as the most used.
The load is part of the result. ITIA quotes HV10, the review HV30, and a 2024 review's table of spark-plasma-sintered grades micro-Vickers (MHV), so compare figures only when test and load match.
ASTM B294-17 covers Rockwell A (HRA) testing of cemented carbides with a diamond indenter, a 10 kgf (98.07 N) preliminary force and a 60 kgf (588.4 N) total force, for readings of 80 HRA and above. ASTM adds that Rockwell is never the only test to weigh.
For scale: a commercial WC-12 wt% Co material (2022) is listed at 86 to 88 HRA, the best 3D-gel-printed, vacuum-sintered WC-20Co samples in a 2024 review reached 87.7 HRA, and a UPenn lecture says cemented carbide can reach up to 92 HRA (about 80 HRC).
The 2024 review's hardness standards: ISO 3878 (Vickers), ISO 3738 (Rockwell), ISO 22394 (Knoop) and ASTM B294 (cited there as B294-22).
Sources: NTP RoC background document on hard metals (2010); OSTI 1981641: WC-Co grades and grain size (2022); Eclética Química 49 (2024): review of cemented carbide properties and tests; ITIA: Cemented carbides, a success story (newsletter, June 2010); Materials (Basel), December 2024: WC-Co manufacturing review; ASTM B294-17: Rockwell A hardness of cemented carbides; OSTI 1922808: WC-Co and binderless WC materials (2022); University of Pennsylvania IPD 501: Speeds and Feeds lecture.
What hardness costs: toughness and strength
Hardness buys wear resistance and costs toughness. The 2024 review says finer grains and less binder raise hardness, and with it resistance to abrasion wear, but lower fracture toughness; ASTM B294-17 says lower-hardness grades in a compositional group usually have less wear resistance but greater toughness.
Fracture toughness (K1C) is resistance to a growing crack; transverse rupture strength (TRS) is the bending stress a test bar takes before breaking.
| Material | Hardness | K1C, MPa·m½ | TRS, MPa |
|---|---|---|---|
| WC, 6% Co | 1450 HV10 | 12 | – |
| WC, 20% Co | 800 HV10 | 25 | – |
| WC-12% Co, submicron | 1450 HV10 | 10 | – |
| WC-12% Co, extra coarse | 1070 HV10 | 20 | – |
| SPS, 2% Co, 0.5 µm powder | 2350 MHV | 6.2 | 2300 |
| SPS, 4% Co, 0.5 µm powder | 2150 MHV | 6.5 | 2640 |
| SPS, 6% Co, 0.5 µm powder | 2050 MHV | 7.3 | 2940 |
| SPS, binderless, 0.2 µm powder | 2600 MHV | 5.1 | 1500 |
The first four rows are ITIA's (2010, HV10); the SPS rows are spark-plasma-sintered lab material from a 2024 review, in micro-Vickers. Compare within a block: in each ITIA pair and across the SPS rows, the harder material is the less tough one; in the SPS block TRS climbed from 2300 to 2940 MPa as cobalt rose from 2% to 6%, and the binderless row was hardest, weakest and least tough.
Toughness figures depend on the test: the review calls the Palmqvist method the most accepted, says it tracks chevron-notch bending from 10 to 14 MPa·m½ for brittle-like grades, and calls it invalid above 14. ASTM B406 calls TRS a quality check on grade powders, not a design value, and says most cemented carbides are brittle, with strength set by internal or surface flaws.
ITIA notes that, unlike alumina or silicon carbide, cemented carbide keeps considerable toughness because it is partly metallic.
Sources: Eclética Química 49 (2024): review of cemented carbide properties and tests; ASTM B294-17: Rockwell A hardness of cemented carbides; ITIA: Cemented carbides, a success story (newsletter, June 2010); Materials (Basel), December 2024: WC-Co manufacturing review; ASTM B406-96(R21): transverse rupture strength of cemented carbides.
Carbide vs tungsten metal, hardened steel and HSS
ITIA lists tungsten metal at 300 to 650 HV30, below even ITIA's softest carbide (about 800 HV10); the hardest, 2800 HV10, is over four times tungsten's top figure, though the loads differ.
High-speed steel (HSS) is a tool steel alloyed with tungsten and molybdenum (M2: 6.0% W, 5.0% Mo, per ITIA), rated on Rockwell C. ITIA says it can be hardened up to HRC 63 to 68; the UPenn lecture gives up to 65 HRC for HSS and 68 to 70 HRC for cobalt grades such as M35 and M42, against about 80 HRC for the hardest carbide.
Heat widens the gap: ITIA says tungsten HSS keeps most of its hardness up to about 550 °C, and a university lecture sums HSS up as high toughness, low hot hardness.
For carbide, binder content matters most when hot. In a 2020 study, 5% and 12% cobalt grades of similar grain size kept similar relative hardness up to 500 °C; at 600 °C and above the 12% grade kept clearly less, and the authors conclude a low binder content favors hot hardness.
Sources: ITIA: Properties and intermediates; ITIA: Cemented carbides, a success story (newsletter, June 2010); ITIA: Tungsten in steel (newsletter, December 2008); University of Pennsylvania IPD 501: Speeds and Feeds lecture; King Saud University: cutting tool materials lecture; Materials (Basel), October 2020: hot hardness of carbide grades.
What hardness means for a worn tool
A worn carbide tool is worn at the edge. Tool life is usually defined as the time to reach a set flank wear width (flank wear is the worn land that forms where the newly cut surface rubs the tool), and carbide edges wear by deformation, cracking and microchipping. The rest of the tool is still carbide.
In ITIA's road-milling example, a 24 g carbide tip wore to 14 to 17 g; an ITIA-hosted paper says 60 to 70% of the original bit weight is left for recycling.
ITIA notes that a carbide end mill gets its final shape by grinding with diamond tools after sintering. NTP names sharpening and grinding as sources of dust that carries both cobalt and tungsten carbide, and there is no need to grind worn pieces before you sell them.
A fine-grained drill and a coarse-grained mining chisel sit at different points on the hardness-toughness trade, and both are carbide; you need no hardness reading to sell either, and the density weight check gives a first sort between carbide and steel. We buy carbide in any form and pay the shipping from anywhere in the US, so send a few photos and a rough weight through the quote form, or read how selling works.
Sources: Precision Engineering (2013): tool life, part 1; Materials (Basel), 2019: wear of uncoated carbide turning titanium; ITIA: Recycling of tungsten, part 1 (newsletter, May 2018); Int. J. Refractory Metals and Hard Materials (2021): tungsten recycling; ITIA: Cemented carbides, a success story (newsletter, June 2010); NTP Report on Carcinogens, 13th edition: cobalt-tungsten carbide profile; AASTMT IM212 lecture: Tool wear and tool life (2017).
Questions people ask
What is the Mohs hardness of tungsten carbide?
About 9, according to an NTP report, which places it slightly below diamond; cobalt, the usual binder, is a 5. Grades themselves are rated in Vickers or Rockwell A.
What is the Rockwell hardness of tungsten carbide?
It depends on the grade, and no single range is on file. A commercial WC-12% Co material in a 2022 study is listed at 86 to 88 HRA, printed WC-20Co samples in a 2024 review reached 87.7 HRA, and a university lecture says cemented carbide can reach 92 HRA, about 80 HRC. ASTM B294 covers carbide readings of 80 HRA and above.
Is tungsten carbide harder than hardened steel?
Most grades are, by a wide margin. ITIA says high-speed steel can be hardened up to HRC 63 to 68, while a university lecture puts cemented carbide at up to 92 HRA, about 80 HRC. The toughest carbide grades, near 800 HV10, sit close to high-strength steels.
Do I need to know the grade or hardness to sell carbide?
No. Tell us what form the pieces are in and about how much they weigh, and add photos through the quote form or by email.
Have tungsten carbide to sell?
Tell us what form it is in and about how much it weighs, and add a few photos. Ship it from any state and we pay the shipping, or we pick up anywhere in California, Arizona and Nevada.