Tribological Properties of Hot-Pressed SrSO₄ Ceramic at Elevated Temperatures in Dry Sliding Against Alumina Ball

SrSO₄ ceramic was prepared by hot-pressed sintering and its friction behavior was investigated against the Al₂O₃ ball under the dry sliding condition from room temperature to 800 °C. From room temperature to 400 °C, the tribological properties of SrSO₄ ceramic are quite poor with the friction coefficients of 0.65–0.83 and the wear rates of about 10⁻³ mm³/Nm. With the testing temperature increasing to 600 °C and 800 °C, a brittle to ductile transition of SrSO₄ takes place because of the activated slip systems. The friction coefficient and wear rate of SrSO₄ ceramic also obviously decrease to 0.37 and about 10⁻⁴ mm³/Nm at 800 °C. The significant improvement of the tribological properties is ascribed to the formation of a smooth and continuous SrSO₄ lubricating film with excellent ductility and low shear strength at elevated temperature. SrSO₄ is considered to be a potential candidate for high-temperature solid lubricant with excellent lubricity.