Microstructure and mechanical properties of WC or Mo2C modified NbC-Ni cermets

In this study, the influence of up to 15 vol% WC or Mo2C addition to Ni bonded NbC matrix cermets, prepared by pressureless liquid phase sintering in vacuum for 90 min at 1390 degrees C was assessed. The constituent phases and W/Mo dissolution in the Ni binder and NbC phases were simulated by thermodynamic modelling. Microstructure and phase analysis using XRD and SEM indicated that the WC or Mo2C modified NbC based cermets were composed of a (Nb,W)C or (Nb,Mo)C solid solution cubic phase dispersed in a cubic Ni alloy binder. Residual WC was present in the cermets with >= 10 vol% WC addition, whereas up to 15 vol% Mo2C addition completely dissolved into the NbC cermets. The phase evolution and influence of the WC/Mo2C content on the solid solution formation is discussed and the fracture toughness, Vickers hardness and transverse rupture strength was assessed.