Microstructure and Properties of PCBN Ceramics Prepared by High Temperature High Pressure Sintering

With ZrO₂, Al₂O₃ and aluminum powder as binders, polycrystalline cubic boron nitride (PCBN) ceramics were sintered by using a six-anvil high-pressure apparatus at a high temperature (1 300-1 600 ℃) and high pressure (5.5 GPa). The effects of sintering temperature on the phase composition, mechanical properties and cutting performance when machining centrifugal cast iron of the ceramics were studied. The results show that the main crystal phases of the PCBN ceramics sintered at different temperatures were composed of cBN, m-ZrO₂, t-ZrO₂, Al₂O₃, AlN and ZrN, and the binding phase particles uniformly dispersed in the cBN matrix. With the increase of sintering temperature, The combination of cBN and the binder phase became tighter, and the relative density, hardness, flexural strength and fracture toughness of the ceramics increased. When the sintering temperature was 1 600 ℃, the ceramics had the best comprehensive mechanical properties, with microhardness, flexural strength and fracture toughness reaching 32.87 GPa, 850.3 MPa and 5.1 MPa·m^1/2, respectively. When the sintering temperature was 1 400 ℃ and 1 500 ℃, the flank wear amount of the PCBN ceramic tool was only 171, 166 μm, respectively, after cutting the centrifugal cast iron rod with a total length of 10 km, indicating that the cutting performance was relatively good.