The X-ray photoelectron spectroscopy depth profiling and tribological characterization of ion- plated gold on various metals

Abstract

An investigation was conducted to examine, by X-ray photoelectron spectroscopy analysis and depth profiling, the atomic nature of such tribological properties as friction and microhardness of ion-plated gold. Friction properties were measured with (1) a gold film, (2) the graded interface between gold and nickel substrate and (3) the nickel substrate. All sliding was conducted against hard silicon carbide pins in two processes. The first is the adhesive process in which friction arises primarily from adhesion between sliding surfaces, and the second is a non-adhesive process, namely abrasion, in which friction occurs as a result of the hard pin sliding against the film, indenting into it and plowing a series of grooves. The other substrates used in this study included copper and 440C stainless steel. Reference experiments were also conducted with vapor-deposited gold on the substrates. A vacuum environment is used in order to maximize the adhesion effect, while oil is used to minimize the adhesion effect. The results of the investigation indicate that the friction related to adhesion as well as the friction related to abrasion are influenced by the coating depth. The trends in friction behavior as a function of film depth are, however, just the opposite. The graded interface exhibited the highest adhesion and friction, while the graded interface resulted in the lowest abrasion and friction. The coefficient of friction due to abrasion is inversely related to the hardness. The greter the hardness of the surface, the lower are the abrasion and friction. The microhardness in the graded interface exhibited the highest hardness due to an alloy hardening effect. Almost no graded interface between the vapor- deposited gold film and the substrates was detected.