Unbonded Tungsten Carbide Ceramics Synthesis at High Temperature and High Pressure

Unbonded tungsten carbide ceramics, with better corrosion resistance, have been widely used in corrosive environment as a substitute for traditional cemented carbides. In addition, this kind of ceramics has better high-pressure resistance and high-speed sliding friction than other ceramics when applied to wear materials.

Recently, some enterprises have used high temperature and high pressure synthesis method to prepare non-binder carbide ceramics. The process does not require binary carbides - molybdenum carbide and tungsten carbide - as raw materials, and does not use any flux to reduce the synthesis conditions. The high purity bulk molybdenum tungsten carbide ceramics are prepared by mixing different components directly and adjusting the composition and purity of molybdenum tungsten carbide by adjusting the synthesis temperature and pressure. The general process is as follows:

Molybdenum powder (Mo), tungsten powder (W) and carbon powder (C) were used as raw materials. After mixing the raw materials and pressing by hydraulic press, the samples were loaded into the synthetic chamber. Graphite heat pipe is used in the assembly chamber, pyrophyllite is used as insulation material, hexagonal boron nitride is used to protect the chamber. The synthesis pressure is 5.0 GPa, the synthesis temperature is 1800 K, the holding time is 60 minutes. After stopping heating, the sample is naturally cooled to room temperature and decompressed to obtain molybdenum tungsten carbide ceramic material. This is a kind of excellent binderless tungsten carbide ceramic.

This process does not need binary carbides as raw materials; does not need any flux (such as metal aluminium etc.); by adjusting the ratio of raw materials, temperature and pressure to improve the purity of molybdenum tungsten carbide, and prepared a high purity bulk molybdenum tungsten carbide material. Thus, the preparation period and sintering time of the traditional method are greatly shortened, and the bulk materials synthesized are conducive to optimizing their physical and mechanical properties.

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