Wear analysis of Cu–Al coating on Ti–6Al–4V substrate under fretting condition

Abstract

Fretting behavior of Cu-Al coating on Ti-6Al-4V substrate was investigated with and without fatigue load. Soft and rough Cu-Al coating resulted in abrasive wear and a large amount of debris remained at the contact surface, which caused an increase in tangential force during the fretting test under gross slip condition. Fretting in the partial slip condition also showed the wear of coating. To characterize wear, dissipated energies during fretting were calculated from fretting loops and wear volumes were obtained from worn surface profiles. Energy approach of wear analysis showed a linear relationship between wear volume and accumulated dissipated energy. This relationship was independent of fatigue loading condition and extended from partial slip to gross slip regimes. As an alternate but simple approach for wear analysis, accumulated relative displacement range was correlated with the wear volume. This also resulted in a linear relationship as in the case of accumulated dissipated energy suggesting that the accumulated relative displacement range can be used as an alternative parameter for dissipated energy to characterize the wear. When the maximum wear depth was equal to the thickness of Cu-Al coating, harder Ti-6Al-4V substrate inhibited further increase in wear depth. Only when a considerable energy was supplied through a large value of the applied displacement, wear in the substrate material could occur beyond the thickness of coating.

On the thermodynamics of degradation

“…Mohrbacher et al (1994) found that wear volume w v (measured via geometry of a wear scar), when plotted versus total friction energy dissipated E m , produced a straight line. Fouvry et al (1997Fouvry et al ( , 2003Fouvry et al ( , 2007, Fouvry & Kapsa (2001), Huq & Celis (2002) and Lee et al (2005) confirmed this linear relation for fretting wear of various coatings on substrates. Dai et al (2000) treated fretting wear as an irreversible thermodynamic process, in a critically stable state near equilibrium, but in the process of transitioning to a new equilibrium state.…”

Fretting Wear Behavior of Cu–Al Coating on Ti-6Al-4V Substrate under Dry and Wet (Lubricated) Contact Condition

“…The wear behavior of Cu-Al coating is obviously very critical since the fretting fatigue improvement of Ti-6Al-4V can be expected only in the presence of coating. Several studies have been undertaken to investigate the wear behavior of Cu-Al coating on Ti-6Al-4V under the various fretting fatigue conditions [9][10][11][12]. In a recent study [12], a dissipated energy approach was successfully used to characterize wear behavior of coating.…”

“…Several studies have been undertaken to investigate the wear behavior of Cu-Al coating on Ti-6Al-4V under the various fretting fatigue conditions [9][10][11][12]. In a recent study [12], a dissipated energy approach was successfully used to characterize wear behavior of coating. This approach involves the quantification of dissipated energy from fretting hysteresis loops and correlating this energy with wear volume [13][14][15].…”

“…This approach involves the quantification of dissipated energy from fretting hysteresis loops and correlating this energy with wear volume [13][14][15]. The results of a previous study showed that there was a linear relationship between wear volume and accumulated dissipated energy, and this relationship was independent of the applied loading condition and fretting regime [12].…”

“…As a continuation of these previous efforts [9][10][11][12], wear behavior of Cu-Al coating system under the wet (i.e., lubricated) contact surface condition was investigated in the present study since a lubricant along with coating is routinely applied in the blade disk attachments of gas turbine engines to decrease the friction between mating components. Further, its counterpart behavior under the dry contact surface condition was also investigated in the exactly similar conditions for the sake of comparison.…”