Designing Cu chemical distribution in Ti(AlCu)N coatings for enhanced erosion-corrosion and antibacterial performance

Abstract

In order to enhance the erosion-corrosion resistance and antibacterial property simultaneously, we prepared PVD TiAlCuN coatings with periodically modulated TiAlCuN/TiAlN sublayers near the topmost surface. Firstly, Ti (AlCu)N phase and Cu nano-precipitates formed in TiAlCuN sublayers can improve coating mechanical performance. Secondly, apart from reducing galvanic corrosion potential, the Cu ions could preferentially diffuse upward to the topmost surface, along the grain boundaries in the columnar TiAlN sublayers, leading to Cu ions at the topmost surface and good antibacterial property. The interfaces between TiAlN and TiAlCuN sublayers can act as multiple barriers to crack propagation and prevent severe coating spallation. The optimized coating exhibits i) the lowest cumulative mass loss and erosion-corrosion rate after 24 h erosion-corrosion testing, which associates with the improved mechanical property and good corrosion resistance, and ii) excellent antibacterial property against Escherichia coli (E. coli) with an antibacterial rate of 99.68 % and a live/dead bacteria proportion of 7.40 %/92.60 %, due to the advanced homeostasis work of the primordial surface Cu ions. The design of modulating the surface Cu chemical distribution achieved by subsurface column-layer architecture provides a new design concept for incorporation of Cu in coatings for the applications of metal parts in critical marine environment.