High temperature mechanical properties of Al2O3-based ceramic tool material toughened by SiC whiskers and nanoparticles

The mechanical properties especially the high temperature mechanical properties of cutting tool materials have significant effects on the cutting performance. A new kind of Al2O3-based ceramic tool material (AW20P5) synergistically toughened by SiC whiskers and nanoparticles was fabricated with good mechanical properties at room temperature, and then the high temperature mechanical properties and their evolution mechanisms from 700 °C to 1200 °C of AW20P5 were investigated compared with the room temperature mechanical properties. The results showed that the flexural strength firstly increased and subsequently decreased with the increasing of the testing temperature. The maximum flexural strength was 673 MPa at the testing temperature of 850 °C. With the increasing of the testing temperature, the fracture toughness of the AW20P5 tool material firstly decreased continuously from 700 °C to 1100 °C but subsequently increased at 1200 °C accompanied with the obvious plasticity. Combining the scanning electron microscope (SEM) and X-ray diffractometer (XRD) analysis, it was concluded that the degradation of the mechanical properties at elevated temperatures was ascribed to the oxidation of SiC and the decrease of its elasticity modulus, the improvement of the mechanical properties at elevated temperatures was ascribed to the healing of the micro cracks and defects as well as the decrease of the interfacial bonding strength.