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. •The durability of a WC/a-C:H coating with a microstructure specifically optimized to withstand high stress cycle rolling contact is studied as a function of normal and shear stress in rolling and rolling/sliding contact.•The wear rate of the coating was found to depend upon the roughness of its substrate, the contact stress, and the magnitude and direction of the slide to roll ratio.