Interfacial microstructure of sintering composites of PCBN grains-graphite particles-CuSnTi alloy

Sintering experiments of Cu-Sn-Ti alloy, polycrystalline cubic boron nitride(PCBN) abrasive grains and graphite particles were carried out at the heating temperature of 920℃ with the dwell time of 30 min. The strength of sintering bulks was measured by means of the three-point bending experiments. The interfacial microstructure and the phases of the sintering bulks were characterized using scanning electron microscope(SEM), energy dispersion spectrometer(EDS) and X-ray diffraction(XRD). The results reveal that in the case of the graphite content of 5~15 wt%, the bending strength of the composite bulks is above 91 MPa, which is much higher than that of the bulk strength of the vitrified grinding wheels. The elemental diffusion behavior has taken place across the joining interface between PCBN grains and Cu-Sn-Ti alloy in the sintering process. The compounds were formed, therefore, the PCBN grains were bonded firmly. Under such condition, the breakage of the PCBN grains has played the most important role in the fracture of the composite bulks. In particular, the breakage mode of the PCBN grains is the intergranular fracture.