Tungsten Carbide Ceramics Preparation by Pressure Free Sintering

Sintered carbide is a combination of high hardness, high toughness and high strength materials, which is due to the existence of a metal bonded phase in tungsten carbide in continuous network form. But sintered ceramics with metal bonded phases have poor mechanical properties at high temperature and have been proved to be easy to corrode. Therefore, people are replacing other ceramic materials with more chemical stability.

So in 2010, a cemented carbide company without any metal bonding phase was developed by a cemented carbide company abroad. It is called VM tungsten carbide ceramic, which not only improves its mechanical properties, but also enables the material to be used at high temperature.

VM tungsten carbide ceramics is a new type of tungsten carbide with high density and non metal bonding phase. This kind of ceramic is a mixture of tungsten carbide powder and selected additives to make the mixed powder form and make no pressure sintering at high temperature to achieve the density. The new microstructures containing needle like second phase particles can improve the mechanical properties of the products at high temperature and improve the chemical stability. This new type of VM tungsten carbide ceramics contains 2 phases, of which tungsten carbide is more than 99% mass fraction. The strength of VM tungsten carbide is 500 ~ 600MPa, and the hardness of Vivtorinox is 15 ~ 17GPa. The structure is exchanged by solid state diffusion during sintering and does not contain any cryogenic phase. The average grain size of tungsten carbide is between 5~10 um, and its porosity is not more than l ~ 2% (volume percentage). The grain of tungsten carbide is equiaxed and irregular in shape, while the second phase particles are in the shape of long grain. This microstructure can effectively inhibit the crack propagation and can be toughened for the toughened tungsten carbide matrix.

New tungsten carbide ceramic materials have many uses, non-metallic binder phase has greatly improved its high-temperature mechanical properties and oxidation resistance, corrosion resistance. Therefore, the tungsten carbide ceramic is a powerful competitor for high speed metal cutting and the application of ceramic cutting tools at present. Other potential applications include applications in chemical, petrochemical, mining, metal ceramic sealing, drainage sprinklers and various machine liners.

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