Effect of plasma surface treatment on the interface properties of DED-arc plasma deposition of Al-4046 wire on Al-7075 substrate

Abstract Direct Energy Deposition (DED)-Arc Plasma has emerged as a promising Additive Manufacturing (AM) technology for fabricating high-performance and large-volume metal parts through hybrid AM, where semi-finished conventional products are used as substrates for AM deposition. However, producing multi-material components remains one of the challenges due to the interfacial properties, intermetallic phases, and conditional compatibility of the different alloys to be joined together. The current study investigated the effect of deposition regimes on the substrate-deposition interface properties when combining different substrates (EN AW 7075) and feedstock materials (EN AW 4046) during multi-layer depositions using DED-Arc Plasma. Plasma and mechanical surface treatments were applied to the substrate surface prior to deposition to investigate their effect on the interface properties. The microstructure, second phases, and mechanical properties of the interface were evaluated through optical microscopy (OM), scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), and hardness tests. The structural investigations revealed a well-defined buildup zone (BZ), partially melted zone (PMZ), and heat-affected zone (HAZ). Additionally, interfacial bonding between the buildup and substrate, with no signs of delamination, was observed. The microstructural and mechanical characterisation showed that the localised preheating from plasma treatment resulted in lower porosity percentage, higher penetration, and finer grain structure. However, the larger PMZ and higher grain boundary second phase segregations in the plasma-treated samples caused higher crack propagation and lower hardness. In conclusion, this study provides valuable insights into the effect of pretreatment substrates for hybrid Al-alloys deposition using the DED-Arc Plasma process and unlocks new opportunities for building hybrid structures and repair applications for the process.