Microstructures and mechanical properties of nanoTiN modified TiC-based cermets for the milling tools

Cermets are wear-resistant materials used in cutting tool applications, but in some applications (e.g. the heavy interrupted cutting), their brittleness is still a limitation for extending the range of their utilizations. Recent experiments have shown that nano-modified cermets with nanometer TiN particles distributed at the grain boundaries can acquire high toughening. The materials are composed of hard-phase grains surrounded by a tough binder-phase. The mechanical properties are influenced by ceramic and metal phases. In the present work, first of all, the effect of the binder phases on the microstructures and mechanical properties of the nanoTiN modified TiC-based cermets for the milling tools are investigated in order to further improve their comprehensive properties. Results show that transverse rupture strength (TRS) and fracture toughness are increasing with rising amount of the binder phases, however, the hardness decreases correspondingly. At the same time, the materials based on TiC–Ni–Co have shown some improvement of fracture toughness and transverse rupture strength compared to TiC–Ni cermets. Moreover, the appropriate Mo addition can refine the microstructures of the nanoTiN modified TiC-based cermets, but reduce the toughness of the materials. In the end, fracture analysis photographs indicate that the main failure mode of the tested samples is transgranular and intergranular fracture.