Improving Tribological Properties of Al alloys via Robust One Step Graphene Coatings using Plasma Spraying

In this study, fabrication of graphene nanosheet (GNs) coatings on Al 2014 alloy substrate was carried out using plasma spraying at two different plasma power i.e., 16 and 20 kW. Exfoliation of graphite to GNs was achieved during plasma spraying and the exfoliation was validated by Raman spectroscopy. The tribological behavior of the GNs coating was examined by varying the loads from 5 to 10 N using a steel ball as a counter surface. The highest coefficient of friction (COF) was observed for bare Al 2014 alloy i.e., 0.73, which drastically reduced to 0.17 and 0.06 upon plasma sprayed GN coatings at 16 kW and 20 kW at 10 N load. The wear rates were also drastically reduced by up to 79% and 83% for GN coatings deposited at 16 kW and 20 kW, respectively, compared to bare Al alloy. It was observed that GNs coatings provide self-lubrication with the solid lubricant property of GNs reducing both friction and wear. Additionally, the GNs coatings offered various strengthening mechanisms such as GNs bridging, GNs pull-out, sheared GNs which further helps in enhancing the tribological properties. Hence, GNs coatings can be a suitable candidate for various automobile and aerospace applications considering their role in achieving significant improvement in tribological properties of Al alloys.