Friction and wear properties of reactive hot-pressed TiB2–TiN composites in sliding against Al2O3 ball at elevated temperatures

TiB2–TiN composites with different TiB2:TiN molar ratios of 2:1 and 1:1 were synthesized by the reactive hot-pressing process using Ti, B and BN powders as raw materials. Friction and wear properties of reactive hot-pressed TiB2–TiN composites were evaluated in sliding against Al2O3 ball from room temperature to 700 °C in air. For TiB2–TiN composites, typical break-in stage in evolution of friction coefficients is observed at room temperature. At 700 °C, the friction coefficient of TiB2–TiN composites is relatively low and steady, as contrasted with the data obtained at room temperature and 400 °C. Under all testing conditions, TiB2–TiN composites exhibit small wear rates, which range in the order of 10−6–10−7 mm3/Nm. The specific wear rates of TiB2–TiN composites and the coupled ball decrease with testing temperature. Wear mechanisms of TiB2–TiN composites depend mainly upon testing temperature. At room temperature, mild abrasion is the dominated wear mechanism of TiB2–TiN composites. However, tribo-oxidation as well as mild abrasion plays an important role during wear test at 400 °C. At 700 °C, continuous oxidized films comprised of rutile form on the surface by thermal oxidation, and provide excellent lubrication and protection.