cBN-Al2O3 composites in NaCl environment under high pressure and high temperature conditions

A series of experiments of cubic boron nitride (cBN)-Al2O3 composites was conducted in NaCl environment under a pressure of 5 GPa at 1200–1650 °C using a Chinese multi-anvil high-pressure apparatus. The oxidation resistance of cBN-Al2O3 composites reached 1300 °C, which was 200 °C higher than that of raw cBN powder. The porosity was estimated by the content of NaCl impurities in cBN-Al2O3 composites. The content of NaCl impurity increases with increasing temperature and decreases with increasing Al2O3 level under high pressure and high temperature conditions. cBN+30 vol% Al2O3 sintered at 5 GPa and 1200 °C shows no NaCl impurity, and the Vickers hardness of the sample is 21.6 GPa which is half of cBN+10 vol% Al.