The effect of film thickness on the behavior of polystyrene-coated steel disks under fretting conditions

Abstract

The purpose of this study was to evaluate the effect of film thickness on a polystyrene coating used to prevent fretting corrosion in a steel-on-steel system. The polystyrene coating was applied to a 1045 steel disk and fretted against a 52100 steel ball. Two sets of experiments were employed. The first set evaluated film life by using seven different film thicknesses ranging from 7.9 to 52 um. The results from this set of experiments indicated that a drastic increase in film life occurred for coatings thicker than 40 pm. The other set of experiments was used to study how fretting damage progressed with time and how it was affected by film thickness. For this purpose two film thicknesses, 38 and 52 μm, were used. The results from these experiments led to the speculation that stress and temperature conditions were different in the 38 and 52 μm films. These differences resulted in a milder fretting regime, and therefore longer life, in the thicker film. Optical and scanning electron microscopy and computer graphics were used to study in detail the fretting interface. The fretting mechanisms were explained in terms of mechanical, chemical, tribochemical, and tribophysical effects.