Sintering of cubic boron nitride without additives at 7.7 GPa and above 2000 °C

The sintering behavior of cBN powder with various particle sizes from 0.5 to 12 µm was investigated when sintered at temperatures from 1500 to 2500 °C and pressure of 7.7 GPa without additives. Above 2000 °C, translucent sintered bodies were obtained. Microstructure observation indicated that the optimum sintering temperature was near 2350 °C for fine powders of 0.5 to 1.2 µm and 2 to 4 µm, and slightly higher than 2350 °C for powders from 8 to 12 µm. The fracture toughness of the well-sintered bodies decreased with grain growth above the optimum sintering temperature.