High temperature tribological properties of spark-plasmasintered AL ₂O₃-SrSO₄ self-lubricating nanocomposites incorporated with and without ag addition

Spark plasma sintering (SPS) is employed to fabricate self-lubricating Al₂O₃-SrSO₄ nanocomposites incorporated with and without Ag addition. The friction and wear properties have been evaluated using a high temperature friction and wear tester from room temperature to 600°C in dry sliding against alumina ball. X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive X-ray (EDX) analyzer were used to investigate microstructure and self-lubrication mechanisms of nanocomposites after wear tests at different temperatures. Al₂O ₃-SrSO₄ nanocomposites with optimum compositional combinations exhibit low and stable friction coefficients of 0.22 and wear rates in the order of 10^-5 mm³/Nm at high temperatures. At low temperature, the Ag additives in the composite form a discontinuous lubricating film to effectively reduce friction and wear. With increasing test temperature, plastic deformation of SrSO₄ during sliding plays an important role in formation of lubricating films on worn surfaces to reduce the friction and wear.