Effect of Al-ZrB2-TiC binder systems on microstructure, and mechanical properties of PcBN composites

There has been an increasing demand for cutting tools with excellent strength, and high wear resistance due to the gradual application of high hardness materials such as high-temperature alloys and surface thermal spray coatings. This study proposes a new design of binder for polycrystalline cubic boron nitride (PcBN) composites. The effects of Al-ZrB 2 -TiC binders on the microstructural evolution, mechanical properties, and thermal shock resistance of the PcBN composites were systematically studied. Al melting at its relatively low temperature, which enables liquid-phase sintering, enhances grain bonding, and stimulates chemical interactions among the binder constituents. These reactions lead to the formation of new phases and promote strong grain bonding, resulting in good mechanical properties. In addition, increasing sintering temperature and cBN content are found to significantly improve the mechanical properties of PcBN composites. The PcBN composites exhibit excellent bending strength of 986.55 MPa, hardness of 42.09 GPa, relative density of 97.6 %, and fracture toughness of 7.66 MPa m 1/2 , respectively. After exposure to air at 1000 °C for 30 min followed by water quenching, the residual flexural strength remained as high as 866.89 MPa, indicating good thermal shock resistance.