Lubricated friction of laser micro-patterned sapphire flats

The technique of laser ablation was employed to create groove-type patterns of different dimensions on sapphire flats. A thin film of a liquid lubricant was deposited on the patterned surface. Comparative pin-on-disk tests revealed a pronounced effect of the pattern on the tribological characteristics of the flats. The presence of the grooves drastically extended the sliding life. If the grooves were too large, the sliding life was limited by excessive wear of the steel ball, while with sufficiently fine grooves, a steady-state regime with an exceptionally low friction coefficient was approached, after an extended run-in period.