Tailoring hardness and electrochemical performance of TC4 coated Cu/a-C thin coating with introducing second metal Zr

The objective of this study was to develop multifunctional protective biocompatible (Cu, Zr)/a-C: H coatings with good mechanical properties and high corrosion resistance using a sputtering system on the surface of TC4 alloy. Coatings with a higher Zr/Cu ratio showed higher hardness, Young's modulus, and superior bio-corrosion resistance. It was demonstrated that charge transfer resistance of the coating with a higher Zr/Cu ratio enhanced from ∼40 kΩ. cm2 to ∼990 kΩ. cm2 after 168 h of immersion time. The results also showed strong synergistic effects of Cu and Zr, as well as the formation of the zirconium carbide phase on the surface.