Abstract:
cBN@TiO
2 (cubic boron nitride coated with TiO
2) powder and cBN@(TiO
2+C) (cubic boron nitride coated with TiO
2+C) powder were prepared by mechanical dry particle coating technology, and then were heated to synthesize cBN@TiN (cubic boron nitride coated with TiN) powder under condition of 1 600 ℃ and N
2 atmosphere. The phase composition and microstructure of the powders before and after high temperature heat treatment, as well as the reaction mechanism at high temperature were studied. The results show that the surface of cBN particles could be evenly coated with nano TiO
2 and nano TiO
2+C particles by mechanical dry particle coating technology. During high temperature heat treatment, the liquid phase B
2O
3 generated by the reaction between TiO
2 and cBN promoted the phase transformation of cBN into hexagonal boron nitride (hBN), indicating the poor high temperature stability of cBN. A lamellar structure layer composed of TiN phase and hBN phase was formed on the surface of cBN@TiN powder particles prepared with cBN@TiO
2 as raw materials. After adding carbon, TiO
2 preferentially reacted with carbon to form TiN during heat treatment, which inhibited the generation of B
2O
3, and thus reduced the phase transformation content of cBN, indicating the good high temperature stability of cBN. The surface of cBN@TiN powder particles prepared with cBN@ (TiO
2+C) as raw materials formed a particle structure layer mainly composed of TiN.