Incorporation of Graphene-based Materials in Modern Powder-based Processes

Abstract

The incorporation of graphene-based materials into powder-based manufacturing processes offers opportunities to tailor material processing and performance. However, achieving controlled graphene characteristics, retaining its functionality during manufacturing, and developing scalable incorporation methods remain important challenges. This thesis investigates these aspects through graphene oxide (GO) deposition on metallic powders, the retention and tribological performance of graphene-based materials in thermal spraying, and the influence of GO on the laser powder bed fusion (PBF-LB) processing of pure copper.A molecular-level mixing method was developed to deposit GO onto metallic powder particles using APTES as a coupling agent. Adjusting the APTES concentration and GO loading enabled control over coating characteristics and surface coverage. By adapting the mixing conditions and chemical parameters, the methodology was scaled from 20 to 500 g batches that were repeatedly used to produce 10 kg of GO-coated copper powder.Graphene retention and tribological functionality were investigated in Al₂O₃ coatings containing graphene nanoplatelets (GNPs), produced by suspension plasma spraying, and GO-containing WC–Co–Cr coatings, produced by high-velocity air-fuel spraying. Graphene-based materials were retained after deposition in both systems but underwent progressive structural and chemical modification during sliding wear. Synchrotron X-ray spectromicroscopy revealed GNPs retention at the alumina tribosurface, accompanied by carbon redistribution and amorphization beneath the wear track. In WC–Co–Cr, GO incorporation reduced the average coefficient of friction, although the lubricating effect diminished with prolonged wear.For PBF-LB of copper, GO coating reduced powder reflectance and modified the melting behavior. Operando X-ray radiography revealed shallower and less slender keyholes during laser processing. At the same time, complementary metallographic characterization of samples produced using a commercial PBF-LB process indicated a tendency toward wider melt pools, suggesting possible changes in the lateral spreading of molten Cu. GO-coated copper enabled thin-wall fabrication over a broader processing range and exhibited higher relative density than unmodified copper under the investigated conditions. Most of the additional carbon was removed during processing, accompanied by a substantial reduction in oxygen content, suggesting a possible sacrificial role of the GO coating in promoting the reduction of copper oxides, which may contribute to improved wetting and spreading of molten copper.Overall, the findings demonstrate how controlled integration of graphene-based materials into powder feedstocks can influence manufacturing behavior and material performance, with the selected approach determining whether graphene is retained or its functionality is exploited during processing.