Fretting wear behavior of a Cu–Ni–In plasma coating

In some aeronautical applications (in the fan blade/disk dovetail notch, for instance), two parts made of a titanium alloy are to be in contact and a relative motion between them may occur. Due to the poor tribological behavior of Ti–6Al–4V rubbing against itself (high friction coefficient, high wear rate), surface coatings are developed and used in order to protect the titanium alloy surfaces. In this paper, we report on the fretting wear behavior of a Cu–Ni–In plasma spray coating used as a retainer for a solid lubricant film like molybdenum disulphide, and deposited on the root of the fan blades. This study is representative of the case when the solid lubricant is worn off out of the contact. A Cu–Ni–In coating was plasma sprayed to a thickness of 150–200 μm on a shot-peened Ti–6Al–4V cylinder. The coated cylinder was tested against a flat, shot-peened Ti–6Al–4V surface, under linear fretting wear solicitation. The effects of normal force and displacement amplitude, from ±15 to ±50 μm, on the fretting wear behavior of the Cu–Ni–In coating were investigated. Wear properties of the coating and substrate were studied and interpreted through a dissipated energy approach. Moreover, the influence of the Cu–Ni–In coating on the cracking of the Ti–6Al–4V counterbody has been studied: the presence of the coating changes the conditions for which cracks nucleate and reduces the length of the cracks in the Ti–6Al–4V specimen for given experimental conditions.