Ditungsten Carbide

Like tungsten carbide powder (WC powder), ditungsten carbide is also a compound composed of the refractory metal tungsten and the non-metallic element carbon. Its English name is tungsten carbide, with the chemical formula W₂C, and it features a hexagonal close-packed (hcp) crystal structure. Due to slight differences in the crystal structures of WC powder and W₂C powder, their physical and chemical properties, as well as their applications, are also different. Note: The crystal structure of WC can be either a simple hexagonal lattice or a face-centered cubic lattice.

In terms of structure, W₂C belongs to a hexagonal close-packed structure, where the carbon atoms are located in the octahedral interstices formed by six tungsten atoms. In the unit cell, the atomic ratio of W to C is 2:1. Based on different crystal structures, W₂C can be classified into three variants: W₂C (α), W₂C (β), and W₂C (γ), with crystal structures corresponding to CdI₂-type, Fe₂N-type, and PbO₂-type, respectively. Among them, W₂C (α) is stable between 1250–2100 °C; W₂C (β) exists as a metastable phase between 2100–2400 °C and can transform into W₂C (α) under mechanical action; W₂C (γ) is stable between 2450 °C and its melting point.

In terms of physical and chemical properties, ditungsten carbide is a black solid powder with a density of 17.15 g/cm³, a melting point of 2860 °C, and a boiling point of 6000 °C. It possesses high hardness, excellent wear resistance, strong acid resistance, and also exhibits certain reducing and oxidizing capabilities.

As for production methods, W₂C can be prepared by mixing tungsten metal powder and carbon black in a ball mill, followed by pressing into shape and heating in a hydrogen atmosphere at 1550–1650 °C, resulting in the formation of W₂C. Alternatively, W powder can be produced via thermal decomposition of tungsten hexacarbonyl, and then reacted with cobalt (Co); when the temperature exceeds 1150 °C, W₂C is generated.

In terms of applications, ditungsten carbide can be further reduced at high temperatures to produce tungsten carbide powder, which serves as the main raw material for the production of cemented carbides.

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