2013年5月7日星期二

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 760mm of Hg,[9] a thermal conductivity of 84.02, and a coefficient of thermal expansion of 5.8 µm.
Tungsten carbide is extremely hard, ranking ~9 on Mohs scale, and with a Vickers number of 1700–2400. It has a Young's modulus of approximately 550 GPa, a bulk modulus of 439 GPa, and a shear modulus of 270 GPa. It has a very high yield stress at 6800 MPa, but a comparatively low ultimate tensile strength of just 35 MPa.
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, tungsten carbide's resistivity is comparable with that of some metals.
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 binary eutectic. 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.

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