cBN‐reinforced Al₂O₃–Ti(C,N) composites with high toughness sintered under oscillatory pressure

Abstract

High‐toughness Al2O3–Ti(C,N) composites reinforced by cBN particles were prepared by the new oscillating pressure sintering technique. The density, phase, and microstructure evolution of the Al2O3–Ti(C,N)‐cBN composites sintered at different temperatures were studied, and their effects on the mechanical properties were investigated. The results show that when the sintering temperature increases from 1300 to 1500°C, the heat preservation time shortens, whereas the density and interface bonding strength of the composites increase. In addition, cBN particles can play the role of crack bridging and be pulled out when the composites fracture, improving the toughness of the Al2O3–Ti(C,N)–cBN composites. However, when the sintering temperature further rises to 1600°C, a new phase of TiB2 forms, and the solid solubility of C and N in Ti(C,N) increases, leading to a decrease in density and mechanical properties. As a result, when the Al2O3–Ti(C,N)–cBN composite is sintered at 1500°C, its mechanical properties reach the maximum values of 21.5 GPa, 5.7 MPa m1/2, and 731 MPa for hardness, fracture toughness, and flexural strength, respectively.