Preparation and Properties of Cubic BN Sintered Compact with AlN

Abstract

Cubic BN was synthesized from hexagonal BN in the presence of AlN as a catalyst at high temperatures above 1000°C and pressures above 5.5GPa under controlled atmosphere. In order to protect AlN from oxidation during the high pressure and temperature treatment, the addition of benzene to the mixture of hex. BN and AlN was found to be more efficient than that of toluene. Fully dense cubic BN-AlN sintered compacts were fabricated simultaneously with the conversion of hex. BN at 6.5GPa and 1600°C. The Vickers microhardness of the sintered compact of 20mol% AlN-80mol% cubic BN was about 4500kg/mm² at room temperature. Direct bonding of cubic BN grains was observed in the sintered compact.