Research On High Performance Conductive Silicon Nitride Ceramic Tool Materials

Si3N4 ceramics have the characteristics of high hardness,high melting point and good high temperature performance.However,the low toughness and brittleness of the silicon nitride ceramics limit its further development and application.This paper will improve the fracture toughness of silicon nitride based ceramic tool materials by using particle and whisker toughening methods.According to the design principles of silicon nitride composite ceramic tool materials,the appropriate particles and whiskers are selected to improve the comprehensive properties of Si3N4 ceramic materials.Based on the toughening mechanism and sintering mechanism of composite ceramic tool materials,liquid phase hot pressing was used to prepare high performance conductive Si3N4-TiC(particle)and Si3N4-TiC(whisker)ceramic tool materials with TiC particles and TiC whiskers as adding phase,Si3N4 as matrix phase,Y2O3 and Al2O3 as sintering aids is prepared.The TiC whisker is based on TiO2 and C as main materials,NaCl,Ni for whisker growth additives were prepared by carbothermal reduction.The sintering mechanism of Si3N4 ceramics is studied,and the reduction of its surface energy provides impetus for Sintering Densification.The factors that affect the sintering of Si3N4 ceramics are studied.The preparation of Si3N4 based ceramic tool material composite powder was studied,and the experimental scheme of the material was determined.The composition and sintering process of the material were optimized,and the mechanical properties and microstructure of the material were analyzed.In the sintering temperature is 1700 ℃,the holding time is 60min,the sintering pressure was the best sintering process of 30MPa,the preparation of Si3N4-TiC(particle)and Si3N4-TiC(whisker)possesses excellent comprehensive mechanical properties.The mechanical properties of Si3N4-TiC(particle)composite ceramic tool materials are:bending strength 756MPa,fracture toughness 7.36MPa·m1/2,the Vivtorinox hardness 18.46GPa.The mechanical properties of Si3N4-TiC(whisker)composite ceramic tool material are:bending strength 686MPa,fracture toughness 8.12MPa·m1/2,the Vivtorinox hardness 17.56GPa.The toughening and reinforcing mechanism of TiC particles and TiC whisker toughened silicon nitride ceramic tool materials is studied.The improvement of the strength of Si3N4 based composite ceramics is due to the good matching between the toughening phase and the matrix phase,the higher density of the composite ceramic material and the addition of the sintering aids.The improvement of fracture toughness of Si3N4 based composite ceramic material depends on the bridging,pulling out of TiC whisker(particles),the deflection of the crack and the toughening of some β-Si3N4 grains.