In situ synthesis of PcBN composites by Sialon combined with cBN-TiB2-AlN and their properties

Abstract

In this paper, the Sialon phase was synthesized under the conditions of ultra-high pressure (5.5 GPa) and high temperature (1550 °C), and the polycrystalline cubic boron nitride (PcBN) composite was in situ synthesized with TiB2, AlN, Sialon as the binder of cubic boron nitride (cBN). X-ray diffractometry (XRD), universal testing machine, field emission scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM) were used to study the effects of Sialon rod crystal on the phase composition, microstructure and mechanical properties of PcBN composites. The results show that when TiB2 rod crystal is formed in the system, the irregular long rod-like new phase Sialon grows along the [0001] face appears. The mechanics properties and machinery properties of the sintered body were significantly improved due to the formation of Sialon. When the generation amount of Sialon is 30 %, the aspect ratio of Sialon is 3/1– 4/1 at most, with high hardness and strength of 27.49 GPa and 903.741 MPa, respectively, as well as the fracture toughness and wear are relatively favorable, separately 7.387 MPa·m1/2 and 1602, the interface is well bonded and the density is the highest. At this time, the comprehensive performance of the PcBN composite material is most superior.