Study On The Development Of Ti(C,N) Based Cermet Tool Materials And Cutting Performance

As the third generation of cermets, Ti(C,N)-based tool materials have higher hardness and high-temperature strength compared with WC-Co hard alloy. Because of the higher hardness and better wear resistance than Si₃N₄ ceramic tools, the tool is suitable for machining hardened steel and high-strength steel. It has higher fracture toughness and shock resistance than Al₂O₃ ceramic tools and can employ bigger cutting depth and feed rate. So it is necessary to research and develop the advanced Ti (C, N) cermet composite tool materials and to promote its practical application.The effect of the content of rare earth oxides, Al₂O₃ and VC on the microstructure and mechanical properties of Ti(C,N) based tool materials was investigated, and relation between mechanical properties and micro-structures was analyzed. By optimizing the hot pressing parameters, the best sintering conditions are the sintering temperature of 1450℃ , the pressure of 25MPa and sintering time of 30min.The advanced Ti(C,N) cermet tool materials was developed by adding nano-scale Al₂O₃ particles to Ti(C_0.7N_0.3) solid solution which have high comprehensive mechanical properties. The optimal tool material compositions are as follows: 71.4%Ti(C_0.7N_0.3)-15% (Ni-Mo) -0.6%Cr₂C₃- 12%Al₂O₃-1%MgO(in mass). Its average flexural strength, Vicker hardness and fracture toughness are 900MPa, 17.4GPa and 9.95MPa.m^1/2 respectively.The model for Ti (C,N) cermet grain growth was established and primarily verified. It was proven that the theoretical result from the model is in well agreement with that of the experimental result. The toughening mechanisms of micron / nanometerTi (C,N) cermets composite were analyzed and include the transformation of fracture mode, microcracks, crack deflection and crack bridging etc.Cutting performance of advanced Ti(C,N) cermet tools (material numbers are JT8-JT12), cemented carbide tools (YG8 , YT14), ceramic tools (LT55, SG-4) were researched when turning cast irons , 45 anneal steel and 45 hardened steel respectively. The result indicates that the developed cermet tools are suitable for cutting 45 annealing steels and 45# hardened steel, they are superior to YT14 in cutting performance. Especially the tool wear size of JT9 and JT11 is small and the machined surface quality is high. In cutting 45 anneal steels and 45 hardened steels by JT9 and JT11 tools, chips were segments. It can be concluded from the tool wear photograph that the main wear mechanisms of Ti(C,N) tools are abrasive wear on tool flank.