Densification and Phase Transformation of β-SiAlON-Cubic Boron Nitride Composites Prepared by Spark Plasma Sintering

beta-SiAlON-cubic boron nitride (cBN) composites were prepared from beta-SiAlON and cBN powders at 1600 degrees-1900 degrees C under a pressure of 100 MPa by spark plasma sintering. The effects of cBN content and sintering temperature on densification and phase transformation of the beta-SiAlON-cBN composites were studied. When 10-30 vol% cBN was added to beta-SiAlON, the shrinkage rate of the compacts increased. The compacts of beta-SiAlON-BN composites originally containing 10-30 vol% cBN ceased to shrink at a temperature lower than that of beta-SiAlON and the density of the composites increased. The densification of beta-SiAlON-BN composites originally containing > 40 vol% cBN was suppressed. The phase transformation of cBN to hexagonal BN in the beta-SiAlON-BN composite was inhibited to a greater degree than that in the cBN body.