Development and characterization of low friction coatings for protection against fretting wear in aerospace components

Abstract Fretting, in the form of wear and fatigue in contacting components, is a potential damage mode in assemblies that needs to be resisted and minimised by design, and quantified for the purposes of predicting safe life and hence inspection intervals. Fretting damage incorporates cotemporaneous and competing processes of material removal by wear, and fatigue crack initiation. In modern practice low friction coatings are widely used to control fretting damage to components. Two types of low friction coatings were considered in the present study, conventional thermally sprayed dry film lubricant (DFL) coatings, and novel solid coatings deposited using a mechano-chemical route. The study focused on the evolution of two principal parameters characterising the performance of low friction coatings, namely, the coefficient of friction (COF) and the remanent relative thickness (RT). In the present paper we describe the procedures used for performing fretting wear tests on coated systems, and for the characterisation of coefficient of friction and relative thickness evolution in low friction coatings during fretting wear. Results offer improved insight into the progression of fretting wear in coated systems.