Property and application of tungsten carbide

Tungsten - carbon binary system can form two kinds of crystal type of carbide, WC and W2C. WC is not only the main materials for cemented carbide making, but also is the important raw material powder for the preparation of high wear-resistant coating in thermal spraying field. It is featured with high hardness, especially the high temperature hardness. WC can be wetted by C0, Ni, Fe and other metallic melt, Co solution is the best. The mouth can be dissolved in the metallic melts when the temperature are raised above the metal melting point, and falling the temperature can precipitate excellent performance of WC0, making it being material binding phase with drill or nickel and other metal, through high heat sintering or coating process, forming good wear-resisting coating.

Poor resistance to high temperature oxidation is the main disadvantage of WC, it suffers severe oxidation In 500 ℃ ~ 800 ℃ air, we can do preliminary protection for WC particles by coating of heat-resisting and antioxidant metal, or improving the property of heat-resisting and oxidation resistance of WC by forming a composite carbides with TaC, Tic and other solid solutions. WC  heated to 2850 ℃ is still stable in Ar atmosphere, it’s also not affected in the high temperature nitrogen.

Melting point and hardness of W2C are higher than WC, It can form eutectic mixture with WC W2C + WC, Lower melting point, easy casting, this is so called “cast tungsten carbide” or “fusible tungsten carbide”, the average carbon content is 3.8% ~20%<quality>,  W2C is 78% ~ 80% <quality>and WC is 20% ~ 22%<quality>. This kind of cast tungsten carbide is one of the hardest and the most wear-resist materials, and lower costing.

WC powder can bond with co-based powder, Ni-based powder, fe-based self molten alloy powder and Ni- Al bonding composite powder, which is widely used in the preparation of wear-resistant coating, especially in abrasive wear-resistance, Hardfaced wear, clay sand erosion wear and other aspects. Tungsten carbide  powder is mainly used as the material of thermal spray powder.

We can spray the wear-resistant coating with Vacuum plasma spraying and protective atmosphere plasma spraying, but coating adhesive force is not very good. 

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