Mechanical properties of two types of Al₂O₃/TiC ceramic cutting tool material at room and elevated temperatures

Two types of hot pressed ceramic cutting tool material Al₂O₃/TiC_μ and Al₂O₃/TiC_μ/TiC_n were studied in this paper. The mechanical properties of the two were tested at room temperature and elevated temperatures (from 600 °C to 1100 °C). The effect of nano-TiC on mechanical properties of these two types of material at both room and elevated temperatures was also included in this paper. Nano-TiC, as the additive, could increase the probability of occurrence of transgranular fracture mode during the fracture, thus improving the mechanical properties of the ceramic cutting tool at room temperature. At high temperature, however, the addition of nano-TiC led to the decrease of their original mechanical properties due to the softening of grain boundary at elevated temperatures. Adding nano-TiC to the ceramic cutting tool materials could refine the matrix grain, resulting in an increase in grain boundary ratio, which made more grain boundaries soften and slip at elevated temperatures. Another important reason for the decrease of mechanical properties of Al₂O₃/TiC ceramic tool materials at elevated temperatures was the oxidation of TiC. The TiO₂ formed by the oxidation of TiC grains on the surface layer was not dense and cracks were generated at elevated temperatures; the TiC of the inner layer, therefore, continued to be oxidized, leading to even more TiC grains available for oxidation.