Surface damage and wear mechanisms of amorphous carbon coatings under boundary lubrication conditions

A class of amorphous carbon coatings with excellent tribological properties under dry conditions was recently developed at Argonne National Laboratory. In the present study, the performance of three variations of such coatings under the boundary lubrication regime was evaluated, with particular focus on the coating surface damage and mechanical aspect of the wear mechanisms of the coated surfaces. The evaluation employed ball on flat contact geometry in reciprocating sliding motion and three different lubricants. Compared with the uncoated steel surface, the three variations of the coatings evaluated significantly reduced the amount of wear. The surface damage in the coatings consisted primarily of localised crack formation at the local asperity points of contact typical of boundary lubrication regime. The cracks propagated over time, resulting in eventual removal of coating material.