Hydrophobic Reduced Graphene Oxide-Based Ni Coating for Improved Tribological Application

Electrodeposited nickel-graphene oxide (GO) composite coating was produced by pulse electrodeposition method followed by a functionalization with octadecyl amine (ODA) molecules to convert the embedded hydrophilic GO to hydrophobic reduced GO-ODA. Morphology, compositional, and tribological properties were investigated for the functionalized Ni-GO-ODA composite coating. FE-SEM and AFM microscopic studies show the homogeneous presence of embedded GO-ODA particles in the Ni matrix. XRD, EDS, and Raman spectra confirmed the successful functionalization of GO to GO-ODA. Post-functionalization, the water contact angle of the coating shows 111.8 degrees, thereby confirming its hydrophobic nature. Tribological experiments were conducted by using a linear reciprocating ball on flat sliding microtribometer with varying load and sliding speed at ambient dry sliding condition. Experimental results showed that the wear and friction resistance properties were significantly enhanced after functionalization of GO with ODA. With increasing load, the counter surface penetrates into the bulk of the coating and exposes the embedded particles, which further under shear built a surface film which reduces friction. The wear and failure mechanisms of these coatings subjected to tribological testing were also investigated. This work provides a novel approach to design durable functionalized nano-coatings for tribological applications in various industries such as automotive, aerospace, locomotive and renewable energy technologies.