Physical properties of tungsten carbide

Physical properties

Tungsten carbide has a high melting point at 2,870 °C (5,200 °F), a boiling point of 6,000 °C (10,830 °F) when under a pressure equivalent to 1 standard atmosphere (100 kPa),a thermal conductivity of 110 W·m⁻¹·K⁻¹, and acoefficient of thermal expansion of 5.5 µm·m⁻¹·K^−1.

Tungsten carbide is extremely hard, ranking ~9 on Mohs scale, and with a Vickers number of ~2600.It has a Young's modulus of approximately 530–700 GPa,a bulk modulus of 630–655 GPa, and a shear modulus of 274 GPa. It has an ultimate tensile strength of 344 MPa, an ultimate compression strength of ~2.7 GPa and a Poisson's ratio of 0.31.

The speed of a longitudinal wave (the speed of sound) through a thin rod of tungsten carbide is 6220 m/s.

With a low electrical resistivity of (~2×10⁻⁷ Ohm·m), tungsten carbide's resistivity is comparable with that of some metals (e.g. vanadium2×10⁻⁷ Ohm·m).

WC is readily wetted by both molten nickel and cobalt. Investigation of the phase diagram of the W-C-Co system shows that WC and Co form a pseudo binaryeutectic. The phase diagram also shows that there are so-called η-carbides with composition (W,Co)
6C that can be formed and the fact that these phases are brittle is the reason why control of the carbon content in WC-Co hard metals is important.