Friction and wear behavior of laser textured surface under lubricated initial point contact

Laser surface texturing (LST) by dimpling has been shown analytically and experimentally to enhance mixed, hydrodynamic, and hydrostatic lubrication of conformal sliding components. Improvements such as higher load-carrying capacity, higher wear resistance, and lower friction coefficients were observed in LST mechanical seals and thrust bearings. However, under non-conformal concentrated contact, the dimpled surface may have a different effect on the tribological behavior as a result of increased roughness, which may increase abrasive wear on the counterface. This paper discusses the effect of laser-textured surfaces on the tribological properties under a point ball-on-flat contact configuration. Tribological experiments were performed with dimpled flats in a pin-on-disk friction machine at speeds from 0.015 to 0.75 m/s using oils with different viscosity. Disks with dimples having different depths and densities were evaluated. Results showed that disks with higher dimple density produced more abrasive wear on the ball specimen. However, this higher wear rate led to faster generation of conformal contacts and a transition from the boundary to mixed lubrication regime, resulting in a rapid reduction in the friction coefficient with increased ball wear. The wear rate was higher in tests with lower viscosity oils, as expected. Results of the study may be beneficial for optimization of LST technology for industrial application in friction units.

► Tribological performance of LST surfaces in lubricated non-conformal point contact was evaluated. ► LST accelerated the wear of the ball conterface. ► Change in contact geometry due wear led to transition of lubrication regime from boundary to mixed. ► Lubrication regime transition is accompanied by friction reduction.