Tribological effects of different scaled chevron-shaped microstructures on the Stribeck curve of parallel contacts under unidirectional friction

Abstract

Laser surface texturing is a widely used technology to improve the tribological behavior of articulating surfaces. Especially for lubricated contacts working in unidirectional motion, laser-generated chevron shapes are one of the most promising surface designs to reduce friction and wear. But, investigations regarding the effect of different chevron dimensions on the tribological performance of lubricated contacts are still lacking in literature. Therefore, we used a 300-femtosecond laser to apply chevron microstructures with different scaled leg widths (5–400 µm). Friction analyses were performed to determine the Stribeck curve of lubricated ring-on-disk samples at sliding velocities from 2.3 to 0.006 m/s and a constant load of 50 N. Results show that small-scale chevrons (5–40 µm) improve the overall tribological behavior of the contact partners. With small-scale chevrons, friction could be reduced by 29% in the boundary, 85% in the mixed, and up to 56% at the transition point from mixed to the lubrication regime compared to an unstructured reference. With a chevron leg width of 5 µm, a significant shift of the critical velocity for the lubrication regime transition to lower values was observed (reduction by 36% compared to the reference). In contrast, no substantial change of the coefficient of friction was observed with large-scale (leg width 200–400 µm) chevrons.