立方氮化硼(cBN)对Si_3N_4/cBN复合材料力学性能及Si_3N_4相变的影响

Influence of Cubic Boron Nitride on Mechanical Property of Si_3N_4/cBN and Phase Transformation of Si_3N_4

以不同粒径和含量的cBN在六面顶压机中高温高压制备了Si3N4/cBN复合材料。观察了样品的微观形貌、β-Si3N4含量,测试了抗弯强度和密度。结果发现,cBN颗粒形貌和分布状态对β-Si3N4颗粒生长有很大影响,cBN含量在一定范围内,随着cBN粒径的减小,试样的密度和抗弯强度增大。cBN含量达到70%时,由于出现大量"搭桥"结构,影响断面上的正应力和剪力,结果使材料抗弯强度减小。同时"搭桥"结构不利于试样的致密。实验结果对新型刀具材料Si3N4/cBN有指导意义。

Samples of Si3N4/ cBN with different particle size and content were sintered in the cubic press.Microstructure,density,flexural strength and β-Si3N4 content were investigated. The result show c BN morphology has great influence on β-Si3N4 crystal growth. In certain range of cBN content,flexural strength and density increases as c BN particle size decreasing. While c BN content reaches 70% and80%,normal stress and shear force in the fracture surface are affected by a large number of ＂ bridge＂ c BN,resulting in the decrease of flexural strength. ＂ Bridge＂ c BN is harmful to densifying of Si3N4/ c BN.The result has certain guide sense for new style tool material.