Tungsten carbide consists of refractory carbide and bonded metal, of which the sintering process belongs to the liquid phase sintering process. The quantity of liquid phase will profoundly affect the sintering process and the properties of the products. For example, the increase in the amount of liquid phase will be beneficial to densification. And the excessive amount of liquid phase can cause the reduction of the rigidity of the product.

 

 

Benefit of Appropriate Amount of Liquid Phase

1, It is beneficial for liquid phase to cover solid particles fully and evenly. It can reduce the chance of contact between solid particles and restrain the growth trend of particles, thus helping to refine the particles.

 

2, It is good to provide enough space for the rearrangement of grain and to reduce the resistance of rearrangement.

 

Abuses of Excessive Amount of Liquid Phase

1, Reducing the stiffness of the sintered body,

2, Making the product easily deformed in the sintering process.

 

Appropriate Amount of Liquid Phase

In the right amount, liquid phase should just fill the gap between solid particles. It is generally believed that the amount of liquid phase is not more than 35% of the volume. When the quantity is over, the shape and size of the product cannot be guaranteed. If too little, there will be some pores remaining in the sintered body, which will not be filled with liquid, and solid particles will also be sintered and overgrown due to direct contact.

 

Quantity of Liquid Phase

Through the above analysis, we can see that the quantity of liquid phase should not be too low or too high in the process of multicomponent liquid phase sintering. In industrial production, the amount of the liquid phase of tungsten carbide depends directly on the content of the cobalt. It is found that the content of cobalt is more suitable between 3%-25%.

 

When the cobalt content is less than 3% (the amount of liquid phase is too small), the densification will be difficult to carry out. As a result, the sintered products will show brittleness. When the content of cobalt is higher than 25% (the amount of liquid phase is too much), the shape of the sintered product will be difficult to keep and the physical property will be poor.