Microstructure and Mechanical Properties of TiC0.7N0.3-HfC-WC-Ni-Mo Cermet Tool Materials.

Abstract

TiC0.7N0.3-HfC-WC-Ni-Mo cermet tool materials were fabricated by hot pressing technology at 1450 °C. The effects of WC (tungsten carbide) content on the microstructure and mechanical properties of TiC0.7N0.3-HfC-WC-Ni-Mo cermet tool materials were investigated. The results showed that the TiC0.7N0.3-HfC-WC-Ni-Mo cermets were mainly composed of TiC0.7N0.3, Ni, and (Ti, Hf, W, Mo)(C, N); there were three phases: a dark phase, a gray phase, and a light gray phase. The dark phase was the undissolved TiC0.7N0.3, the gray phase was the solid solution (Ti, Hf, W, Mo)(C, N) poor in Hf, W, and Mo, and the light gray phase was the solid solution (Ti, Hf, W, Mo)(C, N) rich in Hf, W, and Mo. The increase of WC content could promote the process of HfC to form a solid solution and the HfC formed a solid solution more easily with WC than with TiCN. The increase of the solid solution made the microstructure more uniform and the mechanical properties better. In addition, the Vickers hardness, flexural strength, and fracture toughness of the TiC0.7N0.3-HfC-WC-Ni-Mo cermet increased with the increase of WC content. When the content of WC was 32 wt %, the cermet obtained the optimal comprehensive mechanical properties in this investigation. The toughening mechanism of TiC0.7N0.3-HfC-WC-Ni-Mo cermet tool materials included solid solution toughening, particle dispersion toughening, crack bridging, and crack deflection.