Author:

Abstract:

NbC-12 vol% Ni cermets were solid state and liquid phase sintered by pressureless sintering at 1300°C and 1420°C. The effects of 5 vol% secondary carbides (Mo2C, WC and/or TiC) additions on the microstructure and mechanical properties of the NbC-Ni cermets were investigated. Solid-state sintering at 1300°C revealed an interconnected (NbC) microstructure with isolated or clustered nickel phase. Liquid phase sintering on the other hand exhibited fully dense cermets with a homogeneously distributed binder. Liquid phase sintering in the NbC-12 vol% Ni system resulted in abnormal grain growth which was suppressed by secondary carbide additions. The pseudo-binary phase diagrams were calculated using Thermo-Calc software. Microstructure and phase analysis were carried out using SEM/EDS and XRD. The best combination of hardness and fracture toughness was found in the NbC-Ni cermets co-doped with 5 vol% Mo2C and WC.