Contact cracking and delamination of thin solid lubricating films on deformable substrates

Abstract

Effects of substrate plastic deformation on the cracking and delamination damage of thin solid lubricating films at sliding contacts were investigated. Diamond-like carbon films were evaluated by using micro-scratch tests. A three-dimensional finite element method was applied to analyze the stress-strain evolution of the film−substrate systems with consideration to the interfacial adhesion. Intense plastic deformations were generated in the softer SUS304 substrate due to the low shear strength, leading to parallel cracks along the track borders. A pile-up effect resulted in the film buckling and fragmentation ahead of the sliding stylus. However, on the harder M50 substrate, angular cracks in DLC films were generated at the trailing edge of the contact area, which led to wing-shaped spallation of the films.