Materials Glossary
Tungsten carbide is the material behind nearly every insert, end mill, and drill this shop sells. It isn't a mineral you dig out of the ground — it's a deliberately engineered composite, built from hard tungsten carbide grains held together by a tough metallic binder, almost always cobalt.
Tungsten carbide cutting tool material — more precisely called "cemented carbide" — is not a naturally occurring mineral. It's a manufactured composite typically made of 70%–97% tungsten carbide (WC) particles by weight, held together by 3%–30% cobalt (Co) metallic binder; nickel is sometimes used in place of cobalt for corrosion-resistant grades. It's produced through powder metallurgy: WC and Co powders are blended, pressed into a green compact, and sintered at high temperature. During sintering, the cobalt partially melts, wets the surface of the WC grains, and bonds them into a dense solid — which is exactly why the material is called "cemented" carbide. Tungsten provides the hard, wear-resistant skeleton; cobalt is the glue that holds it together.
The WC phase itself is extremely hard, roughly 1500–2200 HV, but a pure ceramic that hard would also be too brittle to survive as a cutting edge. That's the role cobalt plays: cemented carbides with a 6%–10% cobalt binder typically measure 1400–1800 HV30 (Vickers hardness) as a composite — slightly softer than pure WC, but dramatically tougher. In plain terms, WC supplies the hardness and wear resistance, and cobalt is what keeps the tool from chipping or fracturing the moment it hits real cutting loads. Every carbide grade is a balance point on that hardness-versus-toughness scale, tuned for the material and application it's meant to cut.
Grain size is just as important as the WC-to-cobalt ratio. Submicron WC grains, roughly 0.5–1.5 μm across, give the best combination of hardness (over 2000 HV) and transverse rupture strength (2500–3500 MPa). Go smaller than 0.5 μm and fracture toughness suffers; go larger than 1.5 μm and both hardness and strength drop off. This is why tool grade and microstructure control is a genuine engineering discipline in carbide manufacturing, not just a matter of "harder is better" — the grain structure has to be engineered for the job the tool is going to do.
Cemented carbide largely holds onto its hardness up to about 500–600°C in an oxidizing atmosphere. Past that range, the tool starts losing its edge, which is exactly why coatings, coolant strategy, and correct cutting speed matter so much in practice — they're what keep the cutting edge inside its effective thermal window during the cut.
Every insert and end mill in this shop starts with the same engineering trade-off: WC hardness balanced against cobalt toughness, tuned by grade and grain size.
Shop Carbide Inserts