Effect of Nb_0.5 and Mo_0.75 addition on <i>in-vitro</i> corrosion and wear resistance of high-speed laser metal deposited Al_0.3CrFeCoNi high-entropy alloy coatings

High-entropy alloy (HEA) coatings offer unique advantages for enhancing the surface properties of biomedical implants, including improved wear and corrosion resistance. In this study, Al0.3CrFeCoNi-based HEA coatings were produced by high-speed laser metal deposition (HS-LMD) with the addition of Nb and Mo. The coatings were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). Electrochemical corrosion tests, including potentiodynamic scanning (PDS) and electrochemical impedance spectroscopy (EIS), were conducted using Hanks' solution at body temperature to simulate the body environment. Wear tests were also performed under both dry and in-vitro conditions. Contact angle measurements were performed to assess the surface wettability, which is crucial for understanding the interaction between the coating and biological fluids. The results demonstrated that the Mo-containing coating exhibited superior corrosion and wear performance under in-vitro conditions. This was due to the slower progression of deeper corrosion attacks in unmelted particles, which minimized the micro-galvanic effects associated with the eutectic structures within these particles. Additionally, the coating's stable microstructure and effective formation of a protective passive layer contributed to its enhanced performance.