Effects of HfN content and metallic additives on the microstructure and mechanical properties of TiC0.7N0.3-based ceramic tool materials

Effects of HfN content and metallic additives on microstructure and mechanical properties of TiC0.7N0.3-based ceramics were investigated. HfN had very weak inhibition effect on TiC0.7N0.3 grain growth. When HfN content increased from 10 wt% to 20 wt%, flexural strength and fracture toughness became higher, but Vickers hardness was around 20 GPa without significant changes. The optimal mechanical properties of TiC0.7N0.3-20 wt%HfN-Ni-Co were that Vickers hardness was 18.93 GPa, flexural strength was 876.17 MPa and fracture toughness was 7.58 MPa m1/2 in this investigation. Ni-Mo additive exhibited better wettability with TiC0.7N0.3 than the other metallic additives. Ni-Mo additive could inhibit TiC0.7N0.3 grain growth effectively and improve mechanical properties of TiC0.7N0.3-based ceramic. The optimal mechanical properties of TiC0.7N0.3-20 wt%HfN-Ni-Mo ceramic was that Vickers hardness was 19.43 GPa, flexural strength was 1235.88 MPa and fracture toughness was 8.46 MPa m1/2 in this investigation. Its toughening mechanism mainly included crack deflection and crack bridging. In addition, the mixed intergranular/transgranular fracture also could improve fracture toughness.