Experimental investigations into fretting wear and damage mechanisms of Inconel X-750 alloy

Abstract

Fretting wear characteristics of Inconel X-750 were investigated under the dry test condition. Ball-on-flat contact configuration was subjected to the oscillatory movement at different sliding amplitudes through the different time duration and normal loading. Fretting tests were carried out according to the American Society for Testing and Materials standards (ASTM D6425) by the high frequency linear-oscillation wear test rig SRV 4 at room temperature with ∼60 % relative humidity. Worn surface morphologies in the case of stick, partial slip and gross slip regimes were examined by 3D optical profiler, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The aim of this research is to study the tribological characteristics of the Ni-based Inconel X-750 superalloy, which is widely used in the air lubricated gas foil bearing applications where contacting surfaces are subjected to fretting motion. It is found that the displacement amplitude and normal load had strong effect on the fretting mode and damage mechanism. Wear mechanisms were associated with the plastically sheared asperities and crack nucleation and propagation during the stick and partial slip regimes, respectively. As the displacement increased, the wear modes were switched to adhesion, abrasion, debris oxidation, delamination and plastic deformation during the gross slip condition. Fretting time dependence was critical in the higher displacement amplitudes where the wear volume loss progressed significantly. However, test duration was less consistent in the stick and partial slip regimes where the wear properties remains unchanged over time.