Preparation Of Sialon-Bonded PCBN

Sialon powder was synthesized by three methods, spark plasma sintering (SPS), vacuum high temperature (VHT), high temperature and high pressure (HTHP),and then Sialon-based PcBN was fabricated under HTHP. Starting powders of Si₃N₄, AlN, Al₂O₃ and SiO₂ used in this experimental are nanometer/micron powder. the Sialon formula was optimized under HTHP through orthogonal experiment; The effect of sintering temperature and holding time on the synthesis of Sialon-based PcBN were discussed. In the experimental, Sialon powder was synthesized by SPS, then a suitable amount of cubic boron nitride (cBN) powders was added, and Sialon-bonded PcBN was prepared under HTHP. The infulence of different surface condition of cBN grit on the structure and performance of PcBN was also discussed.The phase composition of the samples was characterized by X-ray diffraction(XRD). The structure and morpgology of fracture surface were characterized by scanning electron microscope(SEM). The flexural strength of sintered samples was measured by three-point bend method. The densities of sintered sampales were tested according to Archimedes'principle. Microhardness, expansion coefficient and abrasion ratio were also measured by using HVS-1000 vickers hardness apparatus, DIL402C expansion coefficient test apparatus, and DHM-3 abrasion ratio test apparatus, respectively.The results showed that the Sialon phase content of samples prepared from SPS is highest among the three methods, and its content is 96.7wt%, the relative density 99.74%, the microhardness 1662 HV, the fracture toughness 2.76 MPa·m1/2, the flexural strength 470.32 MPa. The optimal sintering parameter of PcBN is 5.5 GPa/1500℃/15 min. The PcBN's bulk density is 3.388 g?cm-3, the microhardness 2125 HV and the abrasion ratio 7178.