Spark-plasma-sintered ZrO2(Y2O3)-BaCrO4 self-lubricating composites for high temperature tribological applications

Self-lubricating ZrO2(Y2O3)-BaCrO4 composites have been fabricated by spark plasma sintering by tailoring the composition. The friction and wear properties in dry sliding against an alumina ball were evaluated by using a SRV friction and wear tester from room temperature to 800 °C. The composites exhibit distinct improvements in effectively reducing friction and wear over a wide temperature range, as compared to the unmodified ZrO2(Y2O3) ceramics. The ZrO2(Y2O3)-50BaCrO4 composite exhibits a friction coefficient of 0.38-0.55 and a wear rate of 1.44 × 10−5 to 5.35 × 10−5 mm3/Nm up to 800 °C. Surface brittle fracture is considered as the dominating wear mechanism of the composite at room temperature. At elevated temperatures, a self-lubricating BaCrO4 fine-grain layer forms on the worn surfaces, and is partially transferred to the counterface to reduce the friction and wear. The plastic deformation of BaCrO4 at elevated temperatures plays an important role to form a well-covered BaCrO4 fine-grain layer at the tribo-contact regions. The effect of sintering temperature on microstructure and tribological properties of the self-lubricating ZrO2(Y2O3)-50BaCrO4 composite has been discussed.