Effects of Normal and Shear Stresses in Rolling and Mixed Mode Contact on the Micropitting Wear of a WC/a-C:H Tribological Coating

The focus of this research was to evaluate the resistance of a WC/a-C:H coating to micropitting damage in rolling/sliding boundary lubricated contacts. Experiments were conducted on uncoated discs and coated rollers in a three-disc-on-roller tribometer. Contributions of surface roughness, slide-to-roll ratio, and substrate hardness on coating performance were studied. Observations gleaned from the experimental results include that the coating on a super-finished roller can withstand contact stresses as high as 1.7GPa in extreme boundary lubrication and nominally pure rolling with no measurable wear. Roughness of the coated component plays a crucial role in coating performance, as well as in the wear on the uncoated counterpart.