Sintering Process of Tungsten Carbide

The sintering process is one of the necessary steps in producing tungsten carbide products. According to the order of sintering, the sintering process can be divided into four basic stages. Let us talk about these four steps in detail and you will know more about the sintering process of tungsten carbide.

1. Removal of Forming Agent and Burn-In stage

Due to the rising temperature, the moisture, gas, and residual alcohol in the spray dry will be absorbed by powder or molding agent till volatilized.

The increase in temperature will lead to gradually forming agents' decomposition or vaporization. Then the forming agent will increase the carbon content of the sintered body. The quantities of carbon content vary with the differences in the forming agent of the different sintering processes.

At the sintering temperature, the hydrogen reduction of cobalt and tungsten oxide does not react strongly if the vacuum decreases and sintering.

With the increase of temperature and annealing, the powder contact stress is gradually eliminated.

The bound metal powder begins to recover and recrystallize. As surface diffusion occurs, the compressive strength increases. The block size shrinkage is weak and can be processed as a plasticizer blank.

2. Solid State Sintering Stage

The sintered body will contract obviously in the solid state sintering stage. In this stage, the solid reaction, diffusion, and plastic flow increase, and the sintered body will contract.

3. Liquid Sintering Stage

Once the sintered body appears liquid phase, the shrinkage is completed quickly. Then the basic structure of the alloy is going to form under the crystalline transition. When the temperature reaches the eutectic temperature, the solubility of WC in Co can reach about 10%. Due to the surface tension of the liquid phase, the powder particles are closed to each other. Therefore, the liquid phase gradually filled the pores in the particles. And the density of the block increases significantly.

4. Cooling Stage

For the final stage, the temperature will drop to room temperature. The liquid phase is going to solidify as the temperature drops. The final shape of the alloy is thus fixed. At this stage, the microstructure and phase composition of the alloy change with cooling conditions. In order to improve alloys' physical and mechanical properties, this characteristic of alloy can be used to heat the cemented carbide.

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