Micro- and macro-tribological properties of SiC ceramics in sliding contact

Surface properties of single-crystalline and polycrystalline silicon carbide (SiC) specimens were measured using atomic force/friction force microscopy, Auger electron spectroscopy and nano-indentation techniques. Running-in behavior during sliding tests in vacuum was studied on self-mated SiC pairs as a function of surface quality produced by machining. Tribological mechanisms were analyzed in short-time tests using a high-resolution micro-tribometer and then were related to results obtained from macro-tribological tests in humid air and in the presence of distilled water. Information on the structure, chemical composition and properties of SiC surfaces resulting from measurements on the nanoscale can be very useful for explaining tribological performance under far different operating conditions such as in vacuum or air, with contact areas ranging from diameters of a few nanometers to one millimeter and initial applied contact pressure from about 1 MPa to 3 GPa. Friction and wear mechanisms are discussed as functions of surface composition and roughness, vacuum and humidity of air.