Cubic BN Sintered with Al under High Temperature and High Pressure

Sintering of cubic boron nitride (cBN) with addition of Al is carried out in the temperature range 1300--1500°C and under the pressure 5.5GPa. When sintered at 1300°C, a weak diffractive peak of hexagonal BN (hBN) is observed in the Al-cBN sample, indicating the transformation from cBN to hBN. No nitrides or borides of Al are observed, which indicated that Al does not react with cBN obviously. When the sintering temperature is increased to 1400°C, the diffractive peak of hBN disappears and new phases of AlN and AlB₂ are observed, due to reactions between Al and cBN. When the sintering
temperature is further increased to 1500°C, the contents of AlN and AlB₂ phases increase and the Al phase disappears completely.