Effect of Ni on mechanical behavior of Al₂O₃/(W,Ti)C ceramic tool materials at ambient and elevated temperatures

Two types of Al₂O₃/(W_0.5,Ti_0.5)C ceramic composites with and without metal phase Ni were studied in this research. The evolution mechanism of bending strength and fracture toughness at both ambient and high temperature(600 ∼ 1000 °C) was studied. The influence of nickel on mechanical behavior and microstructure of composites was also analyzed in the test temperature range. The results showed that the bending strength of both ceramic composites decreased with gradually increased temperature. The bending strength of Al₂O₃/(W_0.5,Ti_0.5)C/Ni was greater than that of Al₂O₃/(W_0.5,Ti_0.5)C ceramic composites at room temperature. However, the bending strength of Al₂O₃/(W_0.5,Ti_0.5)C/Ni decreased more rapidly at high temperature. The fracture toughness of Al₂O₃/(W_0.5,Ti_0.5)C/Ni was always greater than that of Al₂O₃/(W_0.5,Ti_0.5)C at different temperatures. The addition of metal phase had a positive impact on the fracture toughness at different temperatures. It was found that the matrix and the toughening phase were well combined by the metal phase, so the room temperature bending strength of Al₂O₃/(W_0.5,Ti_0.5)C/Ni was enhanced. However, the decrease of interfacial bonding strength caused by the low-melting metal phase led to the fracture mode changed. Moreover, the elastic modulus of Al₂O₃/(W_0.5,Ti_0.5)C/Ni decreased faster at elevated temperatures, which resulted in lower bending strength. The research on the evolution law of mechanical behavior of composites at elevated temperatures has important guiding significance for the design of materials and the choice of cutting parameters. (paper)