Multilayer coatings of periodically co-deposited graphene and ag substrate: Improving the electrified friction interface by modifying the strength-ductility combination

Multifunctional and highly adaptable multilayer coatings are considered the future development trend in the field of protective coating design. To enhance wear resistance when subjected to an electric current and to reduce internal stresses, we developed a multilayer structure in which graphene nanoplatelets (GNPs) were deposited within pure silver using a dual electrolyte alternating deposition technique, resulting in the creation of Ag-Ag/GNP multilayer coatings. In this multilayer coating design, the continuous conductive silver layer enhances the overall electrical properties of the coating, and the soft silver layers absorb part of the internal stress in the coating. The deposited GNPs provide crucial structural reinforcement to the coating, thereby improving its mechanical and tribological properties. These coatings were characterized with respect to their structure and mechanical properties using X-ray diffraction, hardness testing, and electronic tensile testing, and their current-carrying tribological performance was studied. Experiments revealed that the crystal structure of single-layer composite coatings changed with increasing GNP content, whereas the multilayer coatings exhibited improved strength and toughness. In current-carrying tribological tests, the multilayer coatings demonstrated significant adaptability to increasing wear depth and current. The wear mechanism of multilayer coatings transitioned from adhesive to abrasive wear. The results indicate that the multilayer coating design effectively enhances friction stability, reduces electrical contact resistance, and decreases wear volume. The findings of this study provide new insights for the design of multilayer structured coatings and will help reduce the loss of rare metals in electrified friction applications.