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Aiming to enhance the bioactivity and antibacterial characteristics of titanium alloys, Plasma Electrolytic Oxidation (PEO) was employed to create Zn and Sr doped films on Ti6Al4V substrates fabricated by Selective laser melting (SLM). Using an X-ray diffractometer and a scanning electron microscope, the composition and microstructure of the phases were analyzed, and the bioactivity and antibacterial properties were assessed through experiments involving contact angle measurement, cell viability tests, and plate colony counting. Results indicate elevated process voltages with Sr2+ addition, resulting in increased film thickness and surface roughness slightly. PEO films predominantly exhibit rutile and anatase phases. The films display a characteristic discharge microporous structure with an inner barrier layer and an outer porous layer. Elements doped by PEO are uniformly distributed on the film surface. Ca/P ratio of the films can be altered by modifying the concentration ratio of Sr/(Sr + Zn) in the electrolytes. Optimal corrosion resistance is observed at a concentration ratio of 1/4. Compared to SLM-formed titanium alloy substrates, the hydrophilicity of PEO films improves greatly, and co-doping with Sr and Zn significantly enhances cell viability for preosteoblast MC3T3-E1 cells and macrophage RAW264.7 cells. Moreover, the PEO film exhibits notable antibacterial properties. • Films with Sr and Zn content formed on Ti6Al4V by plasma electrolytic oxidation. • Enhanced hydrophilicity of the films doped with Sr/Zn compared to the substrate. • The Sr and Zn co-doped film improved cell viability greatly. • The Sr and Zn co-doped film exhibited significant antibacterial activity. [ABSTRACT FROM AUTHOR]

To enhance the bioactivity and antibacterial activity of titanium alloys, coatings with different content of Zn element were successfully formed on Ti6Al4V substrates by micro-arc oxidation (MAO). The microstructure and composition of the coatings were characterized, and the bioactive and antibacterial activities were evaluated by the contact angle, cell viability and plate colony counting experiments, respectively. The results show that when Zn2+ concentration of the electrolytes rises, the breakdown voltage and the process voltage decrease, while the duration of the micro-arc oxidation stage increases. The products of MAO in the coatings are mainly rutile and anatase phases. As Zn2+ concentration in the electrolyte increases, the content of crystalline phases reduces, the thickness and the surface roughness of coatings increase, and the porosity shows an increase overall. MAO coatings bond tightly to the substrates, forming a thin, dense barrier layer and a thick, porous outer accumulation layer. The increase of Zn content results in an increase of Ca and P content in the coatings and a rise in Ca/P ratio. The concentrations of Ti, O, Ca and Zn elements on the cross-section show a transition distribution. Moreover, the hydrophilicity of all coatings is improved. Zn-doped coatings improve the cell viability of preosteoblast MC3T3-E1 cells and macrophage RAW264.7 cells, and higher cell viability is observed on the coatings with higher Zn concentration. Although the MAO coatings with low Zn content increase bacterial adhesion compared to the substrate, the coatings with high Zn content show adequate antibacterial activity. • Coatings with different Zn content were successfully formed on Ti6Al4V by micro-arc oxidation. • The increase of Zn content results in an increase of Ca and P content as well as Ca/P ratio in the coatings. • Zinc-doped coatings improved cell viability. • The coatings with high Zn content showed adequate antibacterial activity. [ABSTRACT FROM AUTHOR]