The effects of Mo2C additions on the microstructure and sliding wear of TiC0.3N0.7-Ni3Al cermets

Combining hard but brittle Ti(C,N) ceramic particles with the ductile Ni3Al intermetallic produces a ceramic-metal composite, or cermet, with high wear resistance. However, for high N content Ti(C,N) cermets, the wettability of molten Ni3Al is relatively poor, which leads to materials with residual porosity when a low binder volume fraction is used. Through a reaction sintering process, various amounts of Mo2C (from 1.25 to 10 vol.%) were incorporated into TiC0.3N0.7-Ni3Al cermets, with the aim of improving the densification behaviour. Materials were prepared with Ni3Al binder contents from 20 to 40 vol.%, and were densified by vacuum sintering. Mo2C was found to improve upon the wettability during sintering, thus enhancing the densification, especially for the lowest binder contents. The sliding wear and Vickers indentation behaviour of these cermets were assessed. It was found that Mo2C additions had a positive effect on both the hardness and indentation fracture resistance of the samples, but had a detrimental effect on the sliding wear response of the cermets. This behaviour was attributed to increased microstructural inhomogeneity with Mo2C additions.