FAILURE OF TUNGSTEN CARBIDE COBALT ALLOY TOOLS IN MACHINING OF CARBON MATERIALS

Sintered carbon and carbon fibre reinforced plastic composites are often used for functional and structural materials. This paper outlines the machining of these materials using cemented tungsten carbide-cobalt tools. The influence of WC grain size and Co content on tool wear rate when machining carbon materials has been examined and the results compared with those from rubbing tests. In addition, the failure process is discussed from the viewpoint of brittle fracture probability. The main results are as follows. (1) As WC grain size increases, tool wear rate decreases, in spite of a reduction in tool hardness. (2) A decrease in Co content leads to a decrease in tool wear rate. (3) The failure of WC-CO alloy tools is due mainly to the loss of WC particles. This failure process can be fundamentally explained by the probability of brittle fracture.