Research on the amorphous–nanocrystalline heterointerfaces for optimized CoCrFeNiAl protective film growth

In this study, CoCrFeNiAl/Al amorphous–nanocrystalline multi-layer film was fabricated via magnetron sputtering and regulating their heterointerfaces. Their microscopic growth and corrosion protection mechanisms were elucidated by performing characterisations and analyses. Results revealed that after the periodic alternating deposition of high-entropy alloy layers and Al layers, a gradient stress field was induced due to lattice mismatch; this mismatch promoted the preferential orientation growth of nanocrystals. The non-crystalline phase dissipated energy to alleviate local accumulated stress, forming an amorphous–nanocrystalline composite heterointerface. Compared with those of single-layer high-entropy film, the surface roughness of the multi-layer film decreased by 14.2 %, hardness increased by 0.887 GPa, wear rate decreased by 29.95 %, the corrosion potential shifted significantly in the positive direction, and the corrosion current density decreased by approximately one order of magnitude. In summary, this study clarifies the synergistic mechanism of amorphous–nanocrystalline heterointerfaces in mechanical strengthening and corrosion protection and proposes a gradient passivation–structural barrier–self-healing film design. By optimising the crystal structure, the service performance of the multi-layer film was further enhanced in extreme environments, providing theoretical support and key technical guidance for the development of surface protective coatings in marine engineering applications.