Influence of sintering temperature on structure and mechanical properties of polycrystalline cubic boron nitride composites

Abstract

Polycrystalline cubic boron nitride (PcBN) cutting tool materials were prepared by mixing cBN (85 wt.%) and TiN-Ti-Co (15 wt.%) micropowders under high temperature and ultra-high pressure. X-ray diffraction and scanning electron microscopy were employed to analyse the phase composition and microstructure of the composites. The effects of sintering temperature on the mechanical properties and cutting performance of the PcBN ceramics were also investigated. The results indicated that at the ultra-high pressure of 6GPa and temperatures ranging from 1400 to 1700°C, the PcBN composites consist of BN, TiN, TiB2 and Co phases. The PcBN sintered at 1700°C exhibited the most favourable comprehensive mechanical properties, including a flexural strength of 909MPa and microhardness of 36.8GPa. In addition, the cutting tool fabricated from the PcBN composite sintered at 1700°C showed superior cutting performances in testing with 40Cr mechanical parts.

Keywords

• boron nitride
• composites
• ultra-high pressure sintering
• mechanical properties
• cutting tools