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 Al 2 O 3-SrSO 4 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 in dry sliding against alumina ball. Nanosized SrSO 4 powders were synthesized by chemical precipitation process at room temperature and atmospheric pressure. For a comparative study, SrSO 4 solid lubricants with different particle sizes are intentionally designed to investigate the influence of size effect on self-lubricating properties of Al 2 O 3-SrSO 4 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. Al 2 O 3-SrSO 4 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 mm 3 /Nm at high temperatures. With increasing test temperature, plastic deformation of SrSO 4 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 Al 2 O 3-SrSO 4 nanocomposites.