Cemented carbide, often called tungsten carbide or carbide, is a compound material produced by by mixing tungsten carbide and cobalt powder in a certain ratio, pressurizing into various shapes, and then semi-sintering. The sintering process is generally carried out in a vacuum furnace at a very high temperature about 1,300 to 1,500 degrees Celsius.
Carbide sintering is the process in which the tungsten carbide powder are pressed into into powder compact, then heat the powder compact under a sintering furnace at sintering temperature for a certain period of time, and next wait it cool down and the cemented carbide material with required properties will be produced.
The carbide sintering process has four basic stages below：
a. Forming Agent Removal and Presintering
As the temperature increases, the forming agent gradually decomposes or vaporizes at the initial stage of sintering, then eliminating the sintered body.
b. Solid Phase Sintering (800℃ - eutectic temperature)
At this stage,solid-phase reaction and diffusion get intensified and the plastic flow becomes more violent. At the same time, capillary forces due to the wetting liquid act on the solid particles and pull them into close proximity, resulting in rapid shrinkage.
c. Liquid Phase Sintering (eutectic temperature - sintering temperature)
As the liquid phase forms, the shrinkage is quickly completed, followed by a crystallization transition to form the basic structure and structure of the alloy.
d. Cooling (sintering temperature - room temperature)
At this stage, the structure and phase composition of the alloy can be changed vary with different cooling conditions and such kind of feature can be used to improve the physical and mechanical properties of cemented carbide undergo heat treatment.
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