Effect of Granule Size and WC Content on Microstructure and Mechanical Properties of Double Structure Ti(C,N) Based Cermets

The effect of starting granule size and addition of WC on the microstructure and mechanical properties of double structure Ti(C,N) based cermets was investigated. Results show that the Ti(C,N) based cermet granules are homogeneously distributed in the matrix. By increasing the WC content, the amount of hard phases with a white core/grey rim and a coreless structure in the matrix increases. A new phase with a four-layer composite structure is found. With the increase of the granules size, the fracture toughness increases, while the transverse rupture strength (TRS) and hardness show an opposite trend. With the increase of WC content, the fracture toughness and TRS increases, while the hardness decreases. The higher fracture toughness of the double structure Ti(C,N) based cermets is mainly owing to the branching, bridging and deflection of the crack, the formation of micro-cracks near the tip of the main crack, and the pull-out effect of granules.