Ultrafine tungsten carbide has excellent properties such as high strength, high hardness, high wear resistance and so on, which can meet the needs of the development of modern industry and special difficult to process materials. 

 

 

One of the difficulties in the production of ultrafine tungsten carbide is that it is difficult to control the growth of WC grains during the sintering process. And using grain growth inhibitors is one of the most effective ways to control grain growth. The research on grain growth inhibitor mainly focuses on the types, amounts and ways of adding, and the influence of grain growth inhibitors on the microstructure and properties of ultrafine tungsten carbide.

 

Type of Grain Growth Inhibitor

The most widely used grain growth inhibitor in the production of ultrafine crystalline tungsten carbide is the transition element carbide, such as VC, Cr3C2, NbC, TaC, TiC, ZrC, Mo2C, HfC and so on. There are also reports that rare earth, B, P and Cu are used as grain growth inhibitors.

 

Addition of Grain Growth Inhibitor

Effect of grain growth inhibitor is closely related to its addition. Taking carbide inhibitors as an example, with the increase of the amount of carbide inhibitors, the effect of inhibiting grain growth is enhanced. When the amount of addition is reached to a certain proportion, the inhibition effect will not be further enhanced, but the brittle phase will be formed in the alloy, and the strength of the alloy will be reduced.

 

Adding way of Grain Growth Inhibitor

The adding way of grain growth inhibitor determines the distribution of grain growth inhibitors. And the uniform distribution of the grain growth inhibitor component is the key to control grain growth. Therefore, it is very important to choose the appropriate way of adding inhibitor. Generally speaking, there are three methods of adding grain growth inhibitors:

 

1, Add the inhibitor when the ingredients are wet. This is a simple and popular method, but the distribution of grain growth inhibitors is less homogeneous.

2, The inhibitor is added when the tungsten powder is carbonized, which has the best inhibitory effect.

3, Adding the inhibitor when the tungsten oxide has a reduction reaction is an ideal but complex way. The dispersivity of the mixture added in the carbonization phase is the best, and the comprehensive performance is optimal.