Wear mechanisms of TiN–TiB2 ceramic in sliding against alumina from room temperature to 700 °C

TiN–TiB2 ceramic was prepared by the reactive hot-pressing method using titanium and BN powders as raw materials. The friction and wear properties of TiN–TiB2 ceramic were evaluated in sliding against alumina ball from room temperature to 700 °C in air. The TiN–TiB2 ceramic has a relative density of 98.6%, a flexural strength of 731.9 MPa and a fracture toughness of 8.5 MPa m1/2 at room temperature. The TiN–TiB2 ceramic exhibits a distinct decrease in friction coefficient at 700 °C as contrasted with the friction data obtained at room temperature and 400 °C. Wear mechanisms of TiN–TiB2 ceramic depend mainly upon testing temperature at identical applied loads. Lubricious oxidized products caused by thermal oxidation provide excellent lubrication effects and greatly reduce the friction coefficient of TiN–TiB2 ceramic at 700 °C. However, abrasive wear and tribo-oxidation are the dominant wear mechanisms of TiN–TiB2 ceramic at 400 °C. Mechanical polishing effect and removal of micro-fractured grains play important roles during room-temperature wear tests.