Microwave Sintered Silicon Nitride Based Ceramic Tool And Its Cutting Performance Research

Ceramic cutting tools are widely used in high-speed mechining because of its excellent wear resistance?high-temperature resistance?thermal shock resistance and chemical stability.However,the traditional sintering technology has many disadvantages,it can result in non-uniform heating in sintered body?low efficiency and waste of energy.In this paper Si₃N₄ matrix ceramic cutting tool materials with high mechanical properities by microwave sintering were fabricated by designing the material composition?adding the reinforcing phase and optimizing sintering process.Optimized Si₃N₄ matrix ceramic cutting tool materials were conducted cutting tests to study the cutting performance in different cutting parameters in comparison with those of ceramic cutting tools SG4 and cemented carbide cutting tools YS8.Firstly the effect of Si₃N₄ matrix ceramic cutting tool materials microwave sintering progress was investigated.The result showed that sintering temperature is important in microwave sintering Si₃N₄ matrix ceramic cutting tool materials.At 1600? Si₃N₄ fully transformed into elongated ?- Si₃N₄ grains with optimum mechanical properties.The grain conversion ratio was the highest and grew best when sintering for 10min.It shortened at least the two thirds sintering time in comparison with traditional sintering process,which showed the high efficiency and energy-saving of microwave sintering.The effect of the addition of SiC on the mechanical properties of Si₃N₄ matrix ceramic cutting tool materials was studied.The result showed that the microstructure was fine and well-distributed,columnar grains grew completely when the partical size of the reinforcing phase SiC was 100nm.When adding 5wt%SiC it could promote the Si₃N₄ full phase transition,form elongated(3- Si₃N₄ grains,improve hardness and toughness of the materials.Its relative density?hardness and fracture toughness were 96.65%?14.46GPa and 7.33MPa·m1/2 respectively.The cutting performance of hardened 45#steel machining was studied,the optimal cutting parameters of ceramic cutting tool SS were cutting speed v=100m/min,feeding rate f=0.14mm/r and cutting depth a_p=0.1mm.The tool life of ceramic SS was about 4000m,which was shorter than SG4 and YS8,but the surface quality was the highest.The main wear mechanisms were abrasive wear and oxidation wear,there was also adhesion wear.The cutting performance of hardened alloy steel 40Cr machining was studied,the optimal cutting parameters of ceramic cutting tool SS were cutting speed v=100m/min,feeding rate f=0.1mm/r and cutting depth a_p=0.15mm.The tool life of ceramic SS was about 2500m,which was shorter than SG4 and YS8,but the surface quality was the highest.The main wear mechanisms were abrasive wear and oxidation wear.