Modification of Surface and Tribological Properties of DLC Films by Adding Silver Content

Abstract

The incorporation of silver into the diamond-like carbon (DLC) coatings has shown excellent potential in various applications; therefore the surface and tribological properties of silver-containing DLC thin films deserve to be investigated. In this study we have deposited silver-containing hydrogenated and hydrogen-free DLC coatings by plasma immersion ion implantation and deposition (PIII-D) methods. Atomic force microscopy (AFM) and nano-scratch tests were used to study the surface and tribological properties. The silver incorporation had only slight effects on hydrogenated DLC coatings. However, the incorporation of silver has significant effect on hydrogen-free DLC of smoothing the surface and increasing the surface energy. Those effects have been illustrated and explained in the context of experimental results. INTRODUCTIONWhile the effect of adding silver to DLC coatings has been tested to be beneficial in a variety of applications [1][2][3][4][5][6][7][8], the tribological properties of these films are not yet completely understood. In order to justify the application of silvercontaining DLC coatings in various applications, surface analysis and tribological property characterization were carried out for silver-containing DLC coatings deposited by PIII-D methods. In the previous work the composition, microstructure, mechanical and biological properties of DLC-Ag samples have been characterized in details [1]; this manuscript focuses on the surface characteristics of DLC-Ag coatings. The notation of a-C:H and a-C are referred to hydrogenated and hydrogen-free DLC; the corresponding silver-containing samples are referred to a-C:H/Ag and a-C/Ag. AFM was used to image the coatings' surface topography. Mechanical tests of nano-scratch were carried out to characterize the coatings' tribological properties.