WC-Co tungsten carbide is the most common and widely used type of tungsten carbide. The sintering of WC-Co cemented carbide is liquid phase sintering because the composition of Co and WC satisfies the conditions of liquid phase sintering. WC-Co tungsten carbide has the inherent characteristics and requirements of liquid phase sintering, such as wettability, solubility and quantity of liquid phase.

 

 

1, Wettability

Liquid phase sintering requires only complete or partial wetting conditions for liquid phase. That is to say, only when 0°≤wetting angle θ<90°, it can seep into the micropores, cracks and even grain between the particles. The Co liquid is completely wetted by the WC, that is, the wetting angle of theta = 0°.

 

2, Solubility

Liquid phase sintering requires that solid phase solid solution is dissolved in liquid phase, but it cannot be completely dissolved. Only partial dissolving can make sinter enter the dissolution reprecipitation stage. Incomplete dissolution will not lead to the formation of an infinite intersoluble solid solution. Liquid phase sintering cannot be carried out because of the disintegration of the sintered body. When sintering, WC is partially dissolved in Co, and the Co phase is insoluble in WC, which fits the solubility requirement of liquid phase sintering.

 

3, Quantity of Liquid Phase

Liquid phase sintering requires that the sintering system must have a suitable amount of liquid phase, so as to ensure that the liquid phase is fully and evenly coated with solid particles and inhibit particle growth, which is very critical for cemented carbide. The trend provides sufficient space for the rearrangement of particle rearrangement and the reduction of rearrangement resistance. 

 

At the same time, a proper amount of liquid phase does not lead to the reduction of the rigidity of the sintered body and the ability to maintain the shape of the sintered body. When sintering, the temperature is higher than the eutectic temperature of the system, there is always liquid phase in the sintering stage, which is very beneficial to the densification of the cemented carbide.