Tribological Properties of Spark-Plasma-Sintered Al2O3-SrSO4 Self-Lubricating Nanocomposites at Elevated Temperatures

Abstract

Spark plasma sintering (SPS) is employed to fabricate the self-lubricating Al2O3-SrSO4 nanocomposites by tailoring the chemical compositions. Their 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. Nanosized SrSO4 powders were synthesized by chemical precipitation process at room temperature and atmospheric pressure. For a comparative study, SrSO4 solid lubricants with different particle sizes are intentionally designed to investigate the influence of size effect on self-lubricating properties of Al2O3-SrSO4 nanocomposites under the identical test conditions. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate microstructure and self-lubrication mechanisms of nanocomposites after wear tests at different temperatures. Al2O3-SrSO4 nanocomposites with optimum compositional combinations exhibit low and stable friction coefficients of 0.18 to 0.29 and wear rates in the order of 10−3 to 10−5 mm3/Nm at high temperatures. With increasing test temperature, plastic deformation of SrSO4 during sliding plays an important role in formation of lubricating films on worn surfaces of nanocomposites. These lubricating films reduce the friction and wear of the Al2O3-SrSO4 nanocomposites.