The effect of triangle-shaped surface textures on the performance of the lubricated point-contacts

It has been recognized that purposefully designed surface texturing can contribute to the improvement of tribological performance of elements and friction reduction. However, its optimal parameters may depend on the operating conditions. This paper investigated the effect of a triangle-shaped dimples array on the tribological performance of the lubricated point-contacts under different lubrication regimes, based on the rotational sliding experiment of a patterned steel disk against smooth steel balls. The dimples arrays were produced by laser process and characterized by the 3D profilometer. A series of tests were conducted with different dimple parameters including depth, coverage ratio, size, and direction. Stribecklike curves were obtained to depict the transition of lubrication regimes, and the electrical contact resistance was utilized to qualitatively characterize the lubrication status. The test results showed that the dimples arrays with different sizes, depths and coverage ratios had a distinct effect on the friction behaviors. Compared with the nontextured surfaces, when the dimple depth decreased from 30lm to zero with fixed coverage ratio and size, the friction coefficient firstly decreased, and then increased. The friction coefficient finally approached that of the nontextured surface, during which the lowest value appeared at the dimple depth of approximately 10∼15μm. The coverage ratio of texture showed the similar effect on the friction coefficient. Usually, the coverage ratio of approximately 10% resulted in the lowest friction coefficient. The dimple size and direction also had obvious effects on the friction coefficient. Thus, it can be concluded that there exists a set of optimal values for the dimple depth, coverage ratio, size, and direction to realize the friction reduction.