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Within this study, the bearing washer surfaces of cylindrical roller thrust bearings (type 81212, SAE 52100) are laser-patterned with a dot-like pattern (periodicity of 6.5 mm and depth of 1 mm). The wear behavior of the patterned bearings is compared to that of bearings with a ground surface finish. The tribological tests are conducted on an adapted FE-8-test rig using a mineral oil with a low concentration of zinc dialkyldithiophosphate (0.025 wt% P). This study demonstrates an 83% reduction in the wear loss of the laser-patterned bearing. The patterns are able to store wear particles in the topographic minima, thus reducing abrasive wear and therefore the wear loss. Additionally, the formation of a wear inhibiting tribo layer is enhanced as the surface pattern acts as secondary source for the deployed additive.

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The service life of rolling bearings is significantly affected by the film formation in elastohydrodynamic (EHD) contacts, which depends on the operating conditions, like rotational speed or temperature. In grease lubricated EHD contacts, the film formation is determined by the grease consistency and composition, i.e., thickener and base oil type as well as properties of the bleed oil, which is released from the grease during operation. Thus, the film formation of grease lubricated contacts as compared to base oil lubricated contacts can be different. With increasing rolling speed, the film thickness of oil lubricated contacts usually grows. However, in case of grease lubricated contacts, which are not fully flooded, the film thickness remains constant or even decreases with further increasing rotational speed. This effect is referred to as starvation. Since the onset of starvation depends on the grease composition, the film formation of two different grease compositions is investigated in this study. The film thickness measurements are performed on a ball-on-disc tribometer for each grease, as well as the corresponding bleed and pure base oils. Thereby, the characteristic rotational speed leading to the onset of starvation has been identified in dependence of the grease composition and the differences in the lubricating film formation of base oil, bleed oil, and grease lubricated EHD contacts have been discussed. The investigations should help to establish an advanced understanding of the physical mechanisms leading to the onset of starvation to encourage future work with focus on a method to predict the film formation in grease lubricated EHD contacts.