Wear, Friction, and Electrical Noise Phenomena in Severe Sliding Systems

The sliding mechanisms of unlubricated gold and palladium are described. Transfer, roughening, wear, friction, and contact resistance phenomena involve the same discrete events. With rider-flat geometry, severely Worked transfer particles form a prow-shaped wedge which adheres to the smaller member. Even when rider and flat are different, prow material comes from the larger part. Loss of prow occurs by adhesive weld-back transfer and, to form loose debris, by shearing or fatigue fracture. Friction rises in the early stages of sliding as prows grow. Soon, back transfer increases hardness of the larger member and friction falls to an equilibrium level. Friction also falls when prows are kneaded into rollers and become loose debris. During these stages, wear rate diminishes. Contact resistance noise originates in stick-slip, roller formation, surface hardening, and changing composition at the sliding interface when dissimilar contact metals are involved. Contributed by the ASLE Technical Committee on Lubrica...