HARDNESS AND FRACTURE TOUGHNESS OF CEMENTED CARBIDES

The influence of the applied load and microstructure parameters on the traditional Vickers and instrumented indentation hardness and fracture toughness of four WC-Co systems have been investigated. The traditional hardness at higher applied loads is determined mainly by the volume fraction of Co binder. At low loads, the indentation hardness is location sensitive, and it is determined by the size and properties of the WC and binder phase. The scatter in the measured hardness increases with decreasing loads in both methods. In the case of traditional hardness the scatter is controlled by the errors in indent size measurement while the heterogenity of the microstructure is the cause in indentation nanohardness. The fracture toughness of the system with the highest hardness measured by indentation methods is 9.8 MPa m(0.5).