High-entropy CoCrFeMnNi coatings produced by co-electrodeposition and subsequent heat treatment

Developing thick and well-adhered high-entropy alloy (HEA) coatings remains a major technological challenge due to the high cost and complexity of existing deposition methods. This study introduces a novel hybrid approach that combines mechanical alloying, electrochemical co-deposition, and high-temperature annealing to fabricate CoCrFeMnNi-based coatings. In this process, HEA powders obtained by mechanical alloying are suspended in a classical Watts bath and co-electrodeposited with nickel onto copper and steel substrates. Subsequent annealing promotes homogenization and diffusion between the coating and substrate, producing dense layers up to 100 μm thick. Structural and chemical analyses revealed face-centered cubic solid solutions with excellent adhesion and a maximum hardness of 6.25 GPa. The use of co-electrodeposition enables easy incorporation of complex HEA compositions using conventional electrochemical equipment, drastically reducing the cost and process temperature compared with vapor- or laser-based methods. The developed technology not only overcomes the limitations of direct HEA electrodeposition but also allows the deposition of coatings on complex geometries using environmentally friendly aqueous electrolytes. This simple yet versatile approach opens new pathways for producing high-performance protective coatings for applications in energy, aerospace, and nuclear industries, where mechanical robustness and chemical stability at elevated temperatures are critical.