Preparation of Ag-WC-C contacts needs to use tungsten carbide powder and other powder as its raw material; the following is part knowledge of tungsten carbide powder.
Cubic WC1-X is used to represents W - C is a non-stoichiometric composition;
What represent W-C stoichiometric composition are: the hexagonal WC, the hexagonal W2C. At room temperature, only the Six-Party WC is stable.
The hexagonal WC cell structure is staggered triangular prismatic shape, which is Non-Centro symmetric structure, its lattice constant a = 2.916 × 10-10m (hexagonal, a = b), c = 2.844 × 10-10m. Nowadays, the main appliance of tungsten carbide is used to manufacture high-quality carbide, and it can also be used in contact material, metal coating, metal ceramics and other fields.
The lattice constant also known as the lattice parameters, referring to the length of a side of the unit cell, which have a direct contact with the combination of atoms, and it is an important basic parameters of the crystal structure, whose change may reflect changes of the composition in the crystal and status of the force.
Studies have shown that the mechanical property of tungsten carbide is not only related to its composition but the sintering process, and is also closely related to its microscopic crystalline structure. Currently, the preparations methods of tungsten carbide powder methods are:
(1) Tungsten powder is first prepared, and then adds carbon to make it carbonized to obtain tungsten carbide powder;
(2) Preparation of tungsten carbide powder from tungsten carbide compound.
However, both methods have common drawback is that both need a high carbonization temperature (1300 ~ 2000 ℃), the preparation process is complex, and it is costly, what is more, tungsten carbide prepared by this way is usually near-spherical. Using this kind of tungsten carbide powder to prepare plate-like strengthening tungsten carbide powder, there is a need to adopt a special sintering process to make the WC grain growth into a plate, and its orientation is not ideal.
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