Transmission electron microscopy of boundary-lubricated bearing surfaces - Part I: Mineral oil lubricant

Transmission electron microscopy was performed on the near-surface material of tapered roller bearing inner rings (cones) that were tested at two levels of boundary-lubricated conditions in mineral oil with no additives. The near-surface material in an untested steel tapered roller bearing cone was mostly ferrite (with possible martensite), had a grain size gradient as a function of depth and microstructural distortion in the circumferential direction with respect to the cone geometry. Two types of oxide surface layers (or boundary films) were characterized in cross-section, each one corresponding to a different severity of local boundary lubrication during testing. Lubricant analysis was performed on three samples, i.e., untested mineral oil, mineral oil from the 60°C bearing tests, and mineral oil from the 121°C bearing tests. Energy dispersive spectroscopy analysis revealed a significant amount of oxygen and carbon in the cracks. This is an abstract of a paper presented at the 59th STLE Annual Meeting (Toronto, Ontario, Canada 5/17-20/2004).