Fretting Damage of Ni—MoS 2 Coatings: Friction Coefficient and Accumulated Dissipated Energy Evolutions

This article describes fretting wear damage of Ni—MoS₂ coatings in terms of the friction coefficient (COF) and accumulated dissipated energy. Multi-layer dry lubricant coatings containing the elements Mo and S are known to maintain low friction under reciprocal relative displacement, and are considered for this purpose in fan blade attachments within aero-engines. The durability of these coatings for a dovetail connection needs to be investigated in order to help design calculations and overhaul scheduling. Experimental characterization of durability can be achieved by measuring COF as a function of the number of fretting cycles, or, alternatively, the accumulated sliding distance. Dissipated energy is also considered as an alternative indicator for characterizing fretting wear damage. In this article, fretting wear tests with Ni—MoS₂ coatings and various surface treatments were performed using idealized contact geometries and loading conditions similar to those found in aero-engine components. Additionally, COF evolutions of Ni—MoS₂ coatings were numerically determined as a function of accumulated dissipated energy. A direct comparison between a numerical evolution and a measured one was performed, and excellent agreement between the two evolutions was obtained.