Tribological and corrosion properties of PEO/HiPIMS duplex coatings deposited on ZK60 magnesium alloy
In recent years, magnesium alloys have emerged as promising materials for applications such as biomedical implants and automotive components due to their lightweight nature. Their low density, which is close to that of human bone, together with favorable mechanical properties and good biocompatibility, has generated significant interest among researchers. Nevertheless, their industrial use has been restricted because of their high corrosion rate in aggressive environments.
Several studies have explored surface treatments and coating technologies to mitigate this issue, including Physical Vapor Deposition (PVD) coatings. However, PVD coatings applied to magnesium alloys often suffer from drawbacks such as inadequate adhesion, porosity, surface defects, and limited corrosion protection. Consequently, there is a need for coating systems capable of providing stronger adhesion, enhanced corrosion resistance, and suitable mechanical performance for these applications.
A potential solution is the combination of PVD coatings with complementary surface engineering techniques. In this work, Plasma Electrolytic Oxidation (PEO) and High-Power Impulse Magnetron Sputtering (HiPIMS) were combined to produce duplex coatings on ZK60 magnesium alloys. The incorporation of the PEO layer together with the PVD coating aims to improve the adhesion between the coating and substrate by lowering interfacial residual stresses, while also increasing corrosion resistance through the synergistic barrier effect of both layers.
The coatings were characterized in terms of structure and chemical composition using Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS),, and Glow Discharge Optical Emission Spectrometry (GD-OES). Adhesion properties were evaluated through scratch and Rockwell adhesion tests, whereas nanoindentation was employed to determine the mechanical behavior of the coatings. Corrosion performance under static conditions was investigated by potentiodynamic polarization and immersion tests, including measurements of hydrogen evolution and mass loss. Furthermore, tribological experiments were conducted to assess the wear resistance of the coated samples.
The obtained results demonstrated that the duplex-coated samples exhibited superior corrosion and wear resistance, as well as strong adhesion to the substrate and favorable mechanical properties. These characteristics make the developed coatings highly suitable for biomedical applications.