Current-carrying friction of Ag coatings by additive manufacturing: uncovering the role of electric current

Ag coatings by additive manufacturing are a representative high-performance electrical contact materials. Here, an appropriate current of 2 A is introduced during the friction process to optimize the current-carrying friction behavior and anti-wear properties of the Ag coating, such as lower friction coefficient, longer stable wear phase, smoother wear surface and higher wear track hardness. The main reason is that the electroplastic effect of severe plastic deformation generated by friction and Joule heat generated by electric current accelerates the high-density dislocation and grain refinement process, leading to the rapid formation of nanocrystalline structural layers. This work revealed the role of electric current during current-carrying friction in optimizing the microstructure evolution, friction behavior, anti-wear properties, electroplastic deformation mechanism of Ag coatings produced by additive manufacturing.