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 W?C, and it features a hexagonal close-packed (hcp) crystal structure. Due to slight differences in the crystal structures of WC powder and W?C 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, W?C 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, W?C can be classified into three variants: W?C (α), W?C (β), and W?C (γ), with crystal structures corresponding to CdI?-type, Fe?N-type, and PbO?-type, respectively. Among them, W?C (α) is stable between 1250–2100?°C; W?C (β) exists as a metastable phase between 2100–2400?°C and can transform into W?C (α) under mechanical action; W?C (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, W?C 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 W?C. Alternatively, W powder can be produced via thermal decomposition of tungsten hexacarbonyl, and then reacted with cobalt (Co); when the temperature exceeds 1150?°C, W?C 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.
