Study on the composition, microstructure and mechanical properties of PCBN composites synthesized by TiN–AlN–Ti combined with cBN

Polycrystalline cubic boron nitride (PCBN) was synthesized at high temperature and ultra-high pressure, using cBN, TiN, AlN and Ti as starting materials. The effects of CBN content (48–63 wt%) and sintering temperature (1300–1600 °C) on the composition, microstructure and mechanical properties of PCBN materials were studied. X-ray diffraction and scanning electron microscope were used to analyze the phase composition, microstructure and surface crack morphology of PCBN. At the same time, the compactness, microhardness, fracture toughness and flexural strength of PCBN were tested. Research shows that the phase components of PCBN samples are mainly composed of BN, TiB 2 , TiN and AlN. Almost all Ti reacts with cBN during the sintering process to form TiN and TiB 2 phases. When the sintering temperature is 1500 °C, the reaction has been fully completed. When the cBN content increases from 48 to 63 wt%, the relative density, flexural strength and hardness of PCBN increase with the increase in cBN content. When sintered at 1500 °C and the cBN content is 63 wt%, the relative density, flexural strength, fracture toughness and microhardness of the composite are 99%, 820.8 MPa, 6.6 MPa.m 1/2 and 3362 Hv, respectively.