Self-lubricating Cu-MWCNT coatings deposited from an ecofriendly glutamate-based electrolyte

Abstract

Self-lubricating coatings have been studied for a long time due to their convenience compared to systems which need periodic lubrication. For this reason, Cu-CNT composite coatings with high wear resistance and low coefficient of friction were obtained by electrodeposition from an ecofriendly alkaline glutamate-based electrolyte. Deposition experiments were performed at various experimental conditions in the presence of low-frequency ultrasound agitation to ensure particle dispersion and enhance their incorporation in the Cu matrix. Moreover, the effect of 2-Butyne-1,4-diol (an additive use in glutamate-based formulations) on coatings mechanical and tribological properties was assessed. Both pure Cu and Cu-CNT were obtained under all the experimental conditions considered and later characterized by SEM and XRD. Finally, pin-on disk tests were performed to estimate the coefficient of friction and determine the wear resistance. The results showed that incorporation of CNT to the copper matrix led to an improvement of the tribological performance of pure Cu, regardless of deposition parameters. Furthermore, it was found that 2-Butyne-1,4-diol had a strong influence on deposit microhardness and tribological performance, as a result of the changes in microstructure induced by this additive which promoted the development of a (111) texture. Likewise, the incorporation of particles to the Cu matrix promoted changes in surface morphology as well as in the preferred crystalline orientation, promoting crystal growth along the [311] direction. The results indicate that this simple and cheap methodology is suitable for fabrication of self-lubricating coatings.