Research On High Performance Si₃N₄-based Ceramic Tool Materials And Properties

Silicon nitride ceramics have the advantages of high hardness,good oxidation resistance,wear resistance,corrosion resistance,stable chemical properties and excellent high temperature performance.They are a new type of ceramic material with great development potential.Ceramic tools made of high-strength and high-toughness silicon nitride ceramic materials are widely used in the field of high-speed cutting.This article uses α-Si₃N₄ powder as the matrix material,taking TiC whiskers and particles as the toughening and reinforcing phase,rare earth oxides Y₂O₃,Al₂O₃ and TiO₂ are additives.The silicon nitride ceramic tool material with excellent comprehensive performance was successfully prepared by hot pressing sintering process.The effects of sintering aids on the microstructure and mechanical properties of Si₃N₄-based ceramic tool materials were studied.The study found that when the sintering aids Y₂O₃,Al₂O₃ and TiO₂ are used in combination,By adjusting the proportion of each component in the composite sintering aid Y₂O₃-Al₂O₃-TiO₂,the negative effects of the sintering aid can be further reduced,and the performance of the material can be improved.When the ratio of Y₂O₃,Al₂O₃ and TiO₂ is 55.0vol.%:39.2vol.%:5.8vol.%,the bending strength and fracture toughness of the material are greatly improved.The total addition amount of the composite sintering aid also has a significant effect on the performance and microstructure of the composite material.When the total addition amount of the composite sintering aid is 9wt%,the material performance is better,At this time,the flexural strength of the Si₃N₄-based ceramic tool material toughened by TiC particles was 743.9 MPa,and the fracture toughness was 7.4 MPa·m1/2.The sintering temperature and holding time of Si₃N₄-based ceramic tool materials are optimized.Under different process conditions,the composite powder containing 64.5vol.%Si₃N₄,27.7vol.%TiC,4.3vol.%Y₂O₃,3.0vol.%Al₂O₃,0.5vol.%TiO₂ was hot-pressed and sintered.The experimental results show that the sintering temperature is 1700℃,the holding time is 30min,and the sintering pressure is 30MPa,which is the best sintering process for TiC toughened Si₃N₄-based ceramic tool materials.Under the conditions of this sintering process,TiC particles improve the strength and hardness of the material better than TiC whiskers,and TiC whiskers have more advantages in improving the toughness of the material.The flexural strength and Vickers hardness of Si₃N₄-based ceramic tool materials toughened by TiC particles are up to 743.9 MPa and 17.9 GPa,and the fracture toughness is 7.4 MPa·m1/2.The fracture toughness of Si₃N₄-based ceramic tool materials toughened by TiC whiskers is up to 7.9 MPa·m1/2,the bending strength and Vickers hardness are 690.6 MPa and 17.4 GPa,respectively.The toughening and strengthening mechanism of TiC toughened Si₃N₄ ceramic tool materials was studied.The study found that TiC whiskers and particles can not only pull out the cracks during the crack growth process,but also deflect and bridge the cracks,making the cracks difficult to continue to expand,improve the strength and toughness of the material,and affect the TiC toughened Si₃N₄ ceramic tools The factors of the material include grain shape,particle size,porosity,and interface characteristics.