Study on CBN-CBN bonding mechanism in high pressure infiltration sintering of PCBN

Study on CBN-CBN bonding mechanism in the high pressure infiltration sintering of polycrystalline cubic boron nitride(PCBN)was carried out in the CBN-Si system.In the present study,PCBN were sintered under high pressure and high temperature(HPHT)through infiltration method and mixed assembly method,respectively.The raw materials were sintered under 5.0-5.5 GPa,1300-1600℃ and 10-15 min by the assembly-methods mentioned above.The samples were analyzed through XRD,SEM,and hardness test.For CBN-Si system,results showed that CBN did not react with Si under the conditions of 5.0-5.5 GPa and 1300-1600℃ using either infiltration method or mixed assembly method.The samples sintered at 5.5 GPa and 1500℃ contained a large number of CBN-CBN bonding fabricated through the infiltration sintering process.PCBN with a much higher Vickers hardness could be obtain through infiltration sintering method at the same P-T conditions as compared to the mixed assembly method.The high pressure infiltration method was advantageous to plastic deformation and pore closing among the CBN grains,which could improve the densification of sintered samples.The grain-to-grain contact during compression would form local area with high stress,so as to promote molten Si layer infiltration CBN layer and fabricate CBN-CBN bonding among the CBN grain boundary.