Effect of Mo on Morphology Evolution and Mechanical Properties of TiC-Based Cermets

Mo is an important metallic additive in ceramics used for machining and cutting tools. The effect of Mo on the microstructure and mechanical properties of TiC-based cermets has been investigated using scanning electron microscopy (SEM) with energy-dispersive x-ray spectroscopy (EDS), x-ray diffraction (XRD) analysis, Vickers hardness (HV) measurements, and transverse rupture strength tests. The results revealed that addition of Mo greatly affected the morphology of the precipitated carbides in the microstructure of the TiC-based cermets. When the amount of Mo added was low, the undissolved TiC cores observed in SEM images were not completely surrounded by (Ti,W,Mo)C grey rims and a large number of (Ti,W)C bright particles were present in the binder with high W content. Upon increasing the Mo content, Mo combined with more W atoms and precipitated around the cores, causing the number of bright particles to decrease. Crack deflection occurred along the grain boundaries of the wrapped rims and more dimples appeared, which improved the mechanical properties of the cermets. However, excessive Mo content led to formation of thicker grey rims and degraded the mechanical properties. The optimum Mo content was 10 wt.%, which led to moderately sized grey rims and the best mechanical properties.