Spark plasma sintering of cBN(core)/SiO2(shell) powder prepared by rotary chemical vapor deposition

SiO2 nanolayer coated cubic boron nitride (cBN), cBN(core)/SiO2(shell) powder, was prepared by rotary chemical vapor deposition. The cBN/SiO2 powder was densified by spark plasma sintering at 1873 K for 0.3 ks. The hexagonal boron nitride (hBN) phase was not observed in the cBN–SiO2 composites, indicating that the SiO2 nanolayer depressed the phase transformation from cBN to hBN. The relative density of cBN–SiO2 increased with increasing SiO2 content (CSiO2CSiO2). The highest hardness of the cBN–SiO2 composite was 17.5 GPa at CSiO2=38 wt%CSiO2=38 wt% and a load of 0.98 N.