STUDIES OF MECHANOCHEMICAL INTERACTIONS IN THE TRIBOLOGICAL BEHAVIOR OF MATERIALS

Mechanochemical interaction studies can contribute to our understanding of wear and friction of materials. Specific examples of experimental results relative to the subject are discussed. There are two parts to this paper; in one part the synergistic effect of corrosion and wear of iron sliding on sapphire in sulfuric acid is described, and in the other part the effect of surface films on the wear and friction of plasma-deposited diamond-like carbon (DLC) (amorphous hydrogenated carbon) films in sliding contact with silicon nitride is described. The concentration of acid (pH) is an important factor in controlling the iron loss caused by wear-corrosion processes in sulfuric acid. The mechanical action can cause chemical reactions to proceed much faster than they would otherwise. The DLC films are shown to behave tribologically much like bulk diamond. In a dry nitrogen environment, a mechanochemical reaction produces a substance which greatly decreases the coefficient of friction. In a moist air environment, mechanochemical interactions drastically reduce the wear life of DLC films and water vapor greatly increases friction.