Abstract
Composit sintered compacts of the cBN-diamond system were prepared at 7 GPa and 1700°C for 30 min by reaction sintering of the starting powder composed of hBN and diamond. A high conversion yield from hBN to cBN was attained by adding 1 wt% NH4NO3 as a catalyst. An induced transformation from hBN to cBN occurred on the surface of the added diamond seed crystals. The sintered compact prepared from the starting powder having the composition of 70 wt% hBN - 30 wt% diamond, showed a relative density of 99% and an average Vic-kers microhardness of 5100 kg/mm2, which suggested the formation of direct bonding between the transformed cBN grains.
