PRINTING HYDROPHOBIC STAINLESS STEEL GRAPHENE COMPOSITES

Hydrophobic surfaces have low surface energies, which prevents water droplets from wetting the surface. Metals typically have high surface energies leading to highly wettable, hydrophilic behavior. Nano-structuring metallic surfaces could be a way of making a metallic surface hydrophobic potentially leading to improved corrosion resistance, drag reduction, etc. 3Dprinting a metal matrix nanocomposite maybe a scalable method to fabricate hydrophobic metals. Graphene nanoplatelets (GNP) were mixed with 316L stainless-steel (SS) powder and printed on a selective laser melting platform. The composite samples included 0, 1, 2, and 3 vol% GNP. Initial printing jobs ran into some issues that were addressed by adding a vibration source and aluminum foil to the inside of the powder hopper. Additionally, energy density was set higher than 60 J/mm3 to avoid lack of fusion issues. Printing of small and large plates of composite samples was performed at energy densities starting from 60 J/mm3 going up to 100 J/mm3 . As-printed composite sample surfaces consistently exhibited hydrophobic behavior with contact angles exceeding 90°. After polishing, the surfaces exhibited hydrophilic behavior. What is compelling; however, is that while contact angles for pure SS was as expected, i.e., angles < 80°, the composite samples showed angles between 80° and 90°, drawing closer to 90° with an increase in GNP.