Influence of applied pressure on the microstructure and properties of Ti(C,N)-TiB2-Co cermets prepared in situ by reactive hot-pressing

This study investigates the influence of sintering pressure on the microstructure and properties of Ti(C,N)-TiB2-Co cermets prepared by reactive hot processing from a Co-Ti-C-BN system. With increasing sintering pressure, the apparent relative density, fracture toughness and hardness first increase, and then decrease. Cermets with low densities are produced at low applied pressures because liquid cannot infiltrate into the pores, whereas the decomposition of Ti(C, N) and extrusion of cobalt at high pressure produce nano-sized pores that reduce the relative density and mechanical properties. Sintering at 34MPa produces the optimum combination of high apparent relative density (99.8%) with a fine grain size and few crystal defects, which result in a fracture toughness, hardness, and wear groove depth of 6.71 MPa.m(1/2), 19.01 GPa, and 2.2 mu m, respectively. (C) 2016 The Ceramic Society of Japan. All rights reserved.