Lifetime of MoS2 based DFL systems in fretting with and without a Cu-Ni-In under-layer: The dependence on the topography of the surface onto which the DFL is deposited

The superior fretting performance of polymer-bonded MoS2-based dry film lubricant (DFL) coating on a plasma-sprayed Cu-Ni-In under-layer is well known. The Cu-Ni-In under-layer changes both the material and the topography of the surface onto which the DFL is applied. However, the mechanism of how the DFL/Cu-Ni-In interface improves fretting performance requires further investigation. Here, the effects of material and roughness were isolated by using surfaces with the Cu-Ni-In under-layer coating and the TI-6Al-4 V substrate in both the ground and grit-blasted conditions. Increasing Cu-Ni-In surface roughness from 1 µm to 9 µm more than doubled fretting lifetime. The Cu-Ni-In under-layer is shown to provide added durability and extended lifetimes, over fivefold, when compared to Ti-6Al-4 V substrate despite having similar surface topographies.