Development Of Si₃N₄/TiC Nano-composites Ceramic Tool Materials And Study On Their Performance

Aiming at the optimal mechanical properties ,a kind of Si3N4-based nano-composite ceramic tool materials, Si3N4/TiC (denoted as ST) reinforced by nano-TiC were developed successfully. Their sintering behaviors .mechanical properties, friction-wear behaviors as well as cutting performance were studied. The flexural strength of ST ceramic tool material is 920MPa, fracture toughness 7.4MPa-m1/2, and Vicker's hardness 14.75GPa. Research was also carried out on toughening mechanism of nano-composite ceramic material.Fabrication process as well as the effects of the volume fraction of nano-TiC in ST on the mico-structrues and mechanical properties of ceramic tool materials were studied. The principles for the selection of sintering additives in the development of Si3N4-based ceramic tool materials are determined, and the influence of the volume fraction on the sintering behaviors, mico-structure and mechanical properties of Si3N4-based ceramic tool materials are analyzed. The influence of sintering temperature and holding time on the density, micro-structure and mechanical properties of the ceramic tool materials are studied.The toughening mechanisms of nano-composite ceramic material are studied in terms of fracture behavior and residual thermal stresses. The fracture behavior is characterized by crack deflection, twisting, divarication, and stopping or pinning as well as transgranular fracture during the crack propagating as a result of the reinforcment of TiC nano particles. All these fracture patterns contribute to the increase in fracture toughness of the materials.The wear resistance was investigated for three materials with different volume ratio of Si3N4/TiC(82/10 72/20 62/30). It was proved from the wear experiment results that the wear performance of Si3N4/TiC(62/30) is better than those of other two kinds of materials. The wear mechanism are plastic deformation, adhesive wear and spalling.The cutting performance of the Si3N/TiC nano-composites ceramic tools are investigate by means of continuous and intermittent turning of cast iron and hardenedsteel, with parallel experiments conducted using ceramic tools SG-4, LT55 and SNM88. The results manifest that the newly developed ceramic tools are possessed of higher wear and fracture resistance.