Experimental Investigation of Partial Laser Surface Texturing for Piston-Ring Friction Reduction

An experimental study is presented to evaluate the effect of partial laser surface texturing (LST) on friction reduction in piston rings. In a previous study, 30% friction reduction was obtained with full LST where the full width of the piston ring is textured with a very large number of microdimples that act individually as microhydrodynamic bearings. In partial LST, only a portion of the piston-ring width is textured with high dimple density, producing a “collective” effect of the dimples that provides an equivalent converging clearance even with nominally parallel mating surfaces. Experimental results obtained with flat and parallel test specimens with partial LST are presented, confirming a previously published theoretical model and the advantage of partial over full LST. Friction reduction by LST with actual production-crowned piston rings and cylinder liner segments is not straightforward and needs further investigation.