Abstract
Abstract Cu x -Cr-Fe-Mn-Ni high-entropy alloys and their electron-beam-deposited coatings demonstrate a tunable balance of mechanical strength, corrosion resistance, and antimicrobial performance, offering a new paradigm for multifunctional protective materials. Dense nanocrystalline coatings with complex phase coexistence achieved exceptional hardness (~ 9.4 GPa) and a high elastic strain-to-failure ratio (H/E ≈ 0.05), indicating potential for improved resistance to wear and contact damage. Controlled Cu content governs surface oxide composition, simultaneously enhancing corrosion protection and enabling targeted bactericidal activity against Pseudomonas aeruginosa (up to 71% reduction), mitigating microbiologically influenced corrosion (MIC) in saline environments. These results reveal a critical interplay between phase structure, surface chemistry, and functional performance, establishing a rational pathway for designing high-performance coatings and bulk alloys with environment-specific multifunctionality. Cu x -Cr-Fe-Mn-Ni HEAs are versatile candidates for industrial, marine, and energy applications where tailored mechanical, chemical, and antimicrobial properties are required.