Performance and surface analysis of tapered bearings lubricated with a manual transmission fluid

Abstract

The comparative tribological performance of a series of tapered bearings lubricated with a fully formulated manual transmission fluid (MTF) and its PAO base oil was obtained using a KRL thrust bearing tester. Bearing performance was based on the successful completion of an eight hour test procedure created for the KRL tester. Optical microscopy was used to conduct textural analyses on the body contact areas of tested rollers while X-ray photoelectron spectroscopy (XPS) depth profiles were used to collect surface film composition at the previously mentioned contact area. The KRL results indicated that the MTF operated at lower temperatures and performed better than the PAO. This difference was ascribed to the enhanced thermal stability of the additive packages used in the fluid. The optical analyses detected a series of dark bands at the body contact area of all tested rollers indicative of the presence of an EP/AW surface film. XPS depth profiles of the base oil indicated that it generated a mixture of organic carbon and iron oxide which proved ineffective under more severe test conditions. In contrast, the profile of the MTF included a mixture of carbonate, borate, sulfide, phosphates and oxide throughout the film. Finally, the combination of thermal stability and EP/AW film composition was attributed to the better performance of the MTF.