Dissipated energy and friction coefficient evolution during fretting wear of solid lubricant coatings

In this study of key process parameters evolution during fretting wear of solid lubricant coatings for aerospace applications emphasis is placed on the analysis of the energies (total and dissipated) during fretting cycles. Key evolution trends are expressible in power law form, allowing compact and efficient description of the process. Slip ratio and slip index according to Varenberg et al. [3] are considered along the accumulated dissipated energy (ADE) and the global coefficient of friction (COF). Evolution observed admits interpretation in terms of a Kachanov-type damage parameter as a function of the accumulated reciprocal sliding distance (ARSD). Fretting wear tests were performed on samples of dry film lubricant coatings (diamond-like carbon (DLC) and MoS2-containing coatings). Flat-and-rounded contact geometry was used to simulate the conditions observed in aero-engine components. Various pre-treatments (shot peening and grit blasting) were considered. Exponential and power law evolution laws provide convenient descriptions of the damage accumulation process in terms of two parameters (damage rate constant and damage exponent).