Effect of Ni Content on Microstructure and Mechanical Properties of NbC-WC-Ti(C_(0.7),N_(0.3))-Ni Cermets

摘要

In this study, Ni bonded NbC cermets, i.e., NbC-xNi-18WC-14Ti(C_(0.7),N_(0.3)) (wt%) with a Ni from 6 to 20 wt%, were prepared by liquid phase sintering in vacuum for 90 min at 1390 or 1450 °C. Microstructural investigation was performed by SEM and XRD analysis. The phase composition in the cermets were simulated by thermodynamic modelling. All cermets were fully densified. Microstructure and phase analysis indicated that the NbC based cermets were composed of a core-rim structured cubic (Nb,W,Ti)(C,N) phase and a cubic Ni alloy binder. The variation in Ni content resulted in a significant effect on the hardness and toughness of the cermets. The hardness decreased whereas the fracture toughness increased nearly linearly with increasing Ni content. The NbC-9Ni-18WC-14Ti(C_(0.7),N_(0.3)) (wt%) cermets, sintered at 1450 °C, exhibited a good combination of hardness (1500 kg/mm~2) and indentation toughness (～8.8 Mpa.m~(1/2)) as well as a three point flexural strength of 2000 Mpa.