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

Self-lubricating ZrO₂(Y₂O₃)-BaCrO ₄ 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(Y ₂O₃)-50BaCrO₄ composite has been discussed.