7 - Mechanical Behavior of Cemented Carbides

Abstract

The major constituent of cemented carbides consists of fine cemented carbide (WC) particles, which are relatively hard and brittle, and the minor constituent is a cobalt-rich binder phase, which is relatively soft and ductile. While it is generally accepted that the binder phase is continuous, there is a controversy about the degree of continuity of the carbide phase. The structure of the sintered WC–Co alloys consists of dispersed carbide particles embedded in a continuous binder phase, with thin binder film separating the individual carbide particles. According to this hypothesis, only the binder phase plays an important role in the plastic deformation of WC–Co alloys. Several works support this theory and consider the binder mean free path as the controlling structural variable to determine the strength. The second school of thought assumes the presence of a continuous carbide skeleton. In this case, the plastic deformation of the alloy would require considerable plasticity in the carbide, because the carbide skeleton would have to deform in compatibility with the binder phase.