Effect of carbon addition on the densification behavior, microstructure evolution and mechanical properties of Ti(C, N)-based cermets

Abstract

Four cermets with composition of TiC-10TiN-32Ni-16Mo-(9−x)WC-xC (x=0, 0.5, 1.0 and 1.5wt%) were prepared by vacuum sintering. The effect of carbon addition on the densification behavior, phase and microstructure development, hardness (HRA) and transverse rupture strength (TRS) of the prepared cermets was studied. The full densification temperature was almost identical for cermets with carbon addition in the range of 0–1wt%, but it obviously decreased from 1340°C to 1280°C for cermets with excess carbon addition (up to1.5wt%). The carbon addition had no obvious effect on the phase transformation, in all four cermets existed only Ti(C, N) and Ni phases when the sintering temperature was or exceeded 1340°C. However, the carbon addition had a significant effect on the final microstructure of cermets sintered at 1400°C, grey rim phase gradually became thin with increasing carbon addition, which was attributed to the fact that higher carbon addition inhibited the dissolution process of carbides in Ni phase. Accordingly, the content of alloy elements in Ni-based binder phase reduced gradually with increasing carbon addition, resulting in the decrease of Ni lattice parameter. Typically, 1wt% carbon-doped Ti(C, N)-based cermets sintered at 1400°C exhibited good mechanical properties, which was characterized by homogeneous microstructure, moderate thickness of rim phase and a relatively low solution hardened binder phase.