In situ synthesis of polycrystalline cubic boron nitride in cBN–Al–Ti system with different Gd2O3 additions

Abstract

Polycrystalline cubic boron nitride was sintered under high temperature (1400 °C) and high pressure (5.5 GPa) using an in situ synthesis method. The composition, microstructure, relative density and mechanical properties of the polycrystalline cubic boron nitride (PcBN) with different contents of Gd2O3 were studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The results show that the phases of TiB2, TiN, AlN, AlTi2N and GdB6 are formed through in situ synthesis of cBN–Al–Ti–Gd2O3 system. With the Gd2O3 content increasing, the relative density increases and mechanical properties of PcBN begin to increase and then decrease. Proper amount of Gd2O3 can advance the formation of TiB2 and improve the aspect ratio of TiB2. When Gd2O3 content is 1.0 wt%, the PcBN exhibits optimal comprehensive mechanical properties, with a microhardness of 33.35 GPa and a flexural strength of 972.37 MPa.