Study of Fretting Wear in Titanium, Monel-400, and Cobalt—25 Percent Molybdenum Using Scanning Electron Microscopy

Abstract

Damage scar volume measurements taken from like metal fretting pairs, combined with scanning electron microscopy observations, showed that three sequentially operating mechanisms result in the fretting of titanium, Monel-400, and cobalt–25 percent molybdenum. Initially, adhesion and plastic deformation on the surface played an important role. This was followed after a few hundred cycles by a fatigue mechanism, producing spall-like pits in the damage scar. Finally, an oxidation related mechanism became most significant. Damage scar measurements made on several elemental metals after 6 × 10⁵ fretting cycles suggested that the ratio of oxide hardness to metal hardness was a measure of the susceptibility of a metal to progressive damage by fretting.