Enhanced MoAlTiCrNb high-entropy alloy coatings: Achieving superior wear and corrosion resistance via bias voltage tuning

High-entropy alloy (HEA) coatings have recently emerged as promising protective coatings, expected to overcome the shortcomings of poor toughness of ceramic coatings and the lack of wear resistance in traditional corrosion-resistant coatings. In this study, MoAlTiCrNb coatings were prepared using DC magnetron sputtering at various bias voltages (0 V to -250 V). The effects of substrate bias voltage on the coating growth, mechanical properties, tribological properties, and corrosion resistance were investigated. The coatings transitioned from an amorphous structure to a BCC structure as the bias voltage increased. At high bias voltages (-150 V to -250 V), the coatings exhibited delamination attributed to the accumulation of ionic energy promoting crystallization. Adjusting the bias voltage also improved the toughness, wear resistance and corrosion resistance of the coatings. The coatings exhibited the lowest wear rate at -200 V (4.39 x 10-6 mm3 /Nm) and the lowest self-corrosion current density at -100 V (2.34 x 10- 9 A/cm2). The results demonstrate that MoAlTiCrNb coatings have excellent wear and corrosion resistance comparable to ceramic coatings, while retaining good metallic toughness, making them protective coatings under complex operating conditions involving wear and corrosion.