烧结温度对cBN-Al-Ti体系原位合成PcBN的影响
摘要
Polycrystalline cubic boron nitride(PcBN) was prepared under a high temperature and an ultra-high pressure using an <i>in situ</i> synthesis method. The influence of sintering temperature on composition, micro-structure, relative density, porosity and mechanical property of the PcBN was investigated by means of X-ray diffraction(XRD), field scanning electron microscopy(FSEM) and energy dispersive spectroscopy(EDS). The results show that the composition of PcBN is translated from intermediate phases to stable phases consist of TiB<sub>2</sub>, h(hexagonal) AlN and TiN when increasing the sintering temperature in the range of 1400-1600℃ under ultrahigh pressure of 5.5GPa. The cBN particles connect with each other by the reaction product. With the increase of the sintering temperature, the length of rod-shaped crystals of strengthening phase TiB<sub>2</sub> decreases and the pore in surface reduces. There exist the extraction and fracture mechanism of the rod-shaped crystals in the fracture process. The porosity is prominent reducing and the relative density increases when increasing the sintering temperature. With further increasing the sintering temperature to 1600℃, the PcBN exhibits optimal comprehensive mechanical properties with a micro-hardness of 44.1GPa and a flexural strength of 859.3MPa.