ABSTRACT
This chapter presents the fundamental tribology of contaminated surfaces. With contaminated surfaces, however, the chemical activity or inactivity of the metal did not appear to play a role in adhesion. The subjects to be addressed include the effects of surface contamination by the interaction of a surface with the environment, surface contamination by diffusion of bulk elements or compounds, and surface chemical changes with selective thermal evaporation. Most gases, with the exception of the noble gases, adsorb readily to clean metal surfaces; and many adsorb to nonmetals, such as silicon carbide, as well. The effects of oxygen in increasing friction are related to the relative chemical thermodynamic properties of silicon, carbon, and titanium to oxygen. By contrast, adsorption of oxygen on argon-ion-sputter-cleaned, oxygen-ion-bombarded, and reacted oxide surfaces generally decreased the coefficient of friction. The removal of adsorbed contaminants by sliding and the segregation of the oxides increase the adhesion strength and hence the friction.
