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 m^1/2 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.