Micro-electrical discharge coating of AlCoCrFeNi high entropy alloy on MgAz31B to enhance the corrosion and wear resistance

The present research aims to enhance the performance of magnesium alloy (MgAZ31b) in corrosive environments by utilizing high entropy alloy (HEA) coatings, specifically focusing on AlCoCrFeNi. The process involves fabrication of micro-HEA tool by powder metallurgy process and coating preparation by using the fabricated micro tool in electrical discharge coating (EDC) process. The XRD analysis of prepared coating reveals the presence of both body-centered cubic (BCC) and face-centered cubic (FCC) phases. The key findings suggest that the AlCoCrFeNi HEA coating significantly impacts both the corrosion resistance and wear resistance properties of magnesium alloys. Among the different samples, coating prepared at optimum pulse discharge duration (T on = 400μs) emerges as particularly effective, demonstrating a lowest corrosion penetration rate (0.16 mm/year) during electrochemical impedance spectroscopy (EIS) testing compared to the other coated and uncoated magnesium substrate (15.48 mm/year). Moreover, wear tests indicate promising results, with coated surfaces exhibiting improved wear rate (from 0.000145 g/N-m g/N-m to 0.0013 g/N-m) and reduced risk of tribological properties when used in implant applications. The increase in 3D surface roughness after coating was observed which aligns with Wenzel's model, indicating that higher roughness increases the contact angle. The HEA coating with higher 3D roughness than Mg surface exhibits higher contact angle of 95.8° compared to 58.7° for the Mg workpiece. The hydrophobic nature of coating can be advantageous for various biological functions, particularly in protein interactions. Thus, employing high entropy alloy coatings on magnesium alloys holds significant promise for optimizing their corrosion resistance properties, and make more suitable for implant applications.