Directed energy deposition of bronze coatings on aluminium substrates: Microstructure, phase evolution, and process optimization

With the increasing demand for lightweight and wear-resistant components in aerospace applications, the combination of aluminium components with bronze coatings represents a promising approach. Directed Energy Deposition (DED) enables the fabrication of such hybrid structures by depositing wear-resistant copper-based alloys onto lightweight aluminium components. However, the metallurgical interaction between aluminium and bronze alloys is highly complex and often results in the formation of brittle intermetallic compounds at the coating-substrate interface, which can act as crack initiation sites and ultimately lead to delamination. In this study, CuAl10Fe1 and CuAl10Ni5Fe4 bronze coatings were deposited onto EN AW 2024 aluminium alloy using a powder-fed DED process. The influence of nickel on interfacial phase formation and crack susceptibility was investigated by means of optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The results reveal significant differences between both material systems. While the nickel-free CuAl10Fe1 alloy exhibited pronounced interfacial reactions and an increased tendency for crack formation, the CuAl10Ni5Fe4 coatings showed a more stable interface with a reduced crack density. The combined microstructural and phase analyses suggest that the presence of nickel influences the interfacial reaction pathway and is associated with a reduced formation of distinct brittle Cu Al intermetallic regions. The findings demonstrate the importance of alloy composition for the successful deposition of aluminium bronze coatings on aluminium substrates and provide new insights into the role of nickel in improving the interfacial stability of DED manufactured bronze aluminium hybrid structures.