High-temperature tribological properties of spark-plasma-sintered Al2O3 composites containing barite-type structure sulfates

Al2O3–50BaSO4–20Ag, Al2O3–50BaSO4–10SiO2, Al2O3–50(mass%)SrSO4, Al2O3–50PbSO4–5SiO2, Al2O3–50BaSO4 and Al2O3–50BaCrO4 composites (mass%) were prepared by spark plasma sintering and their microstructure and high-temperature tribological properties were evaluated. Al2O3–50BaSO4–20Ag composites (mass%) showed the lowest friction coefficients at the temperature ranging from 473 to 1073 K. Thin Ag film was observed on the wear tracks of the composites above 473 K. In addition, the friction coefficients of Al2O3 composites containing SrSO4 and PbSO4 were as low as those of Al2O3–BaSO4 and Al2O3–BaCrO4 composites at the temperatures up to 1073 K. The thin films formed on the wear tracks of the Al2O3–SrSO4 composites were composed of Al2O3 and SrSO4 phases, while the films formed on the wear tracks of the Al2O3–PbSO4–SiO2 composites consisted of Al2O3, PbSO4 and SiO2 phases.