Modeling contact of Au-coated sphere with rigid flat: Electrical contact resistance, adhesive wear and friction

The electrically conductive coating is an effective means to reduce electrical contact resistance (ECR) of sliding electrical contact, however, the wear resistance of the coated surface influences its reliability and lifetime. The electrical contact performance of coated systems is assessed in this work using the Au-coating/Cu-substrate system. An elastic-plastic coated spherical contact is established with the realistic ductile failure criterion to allow material damage, and the effects of coating thickness and normal loading are investigated. As coating thickness increases, it is found that: the ECR decreases and then increases, presenting minimum value at a thickness independent of normal loading; the static friction coefficient increases which is related to the locations of damage occurrence at sliding inception; the wear coefficient increases to a peak and then decreases. Two wear modes of coated sliding electrical contact are observed, namely debonding mode and detaching mode, where wear particle forms by coating debonding and fracture inside coating, respectively. A critical dimensionless coating thickness, which is the minimum thickness able to protect the coating from debonding, is proposed.