Investigation Of Ti-6Al-4V Surface Microarc Oxidation Electrodeposition Process And Related Properties

Titanium alloys have outstanding mechanical properties and chemical stability and are widely used in aerospace,chemical production and biomedical fields.Among them,Ti-6Al-4V（TC4）has become the major medical implant material due to its good biocompatibility,but its poor fatigue resistance and the release of other trace elements（Al,V）,which can cause nerve damage and functional cellular toxicity in humans,have limited the development of titanium alloys as implant materials in biomedical applications.In this paper,we focus on the surface modification of Ti-6Al-4V alloy by microarc oxidation and electrophoretic deposition,and evaluate the growth of modified film morphology,hydrophobic properties,chemical corrosion characteristics,and in vitro biological antibacterial efficacy.The main studies are as follows:In this article,experiments on microarc oxidation of titanium alloys made by selective laser melting equipment were carried out using an electrolyte consisting of calcium acetate plus disodiumβ-glycerophosphate in constant power mode.The research shows that after selecting a suitable electrolyte,the parameters of forward voltage,pulse frequency,duty cycle and oxidation time in micro-arc oxidation were analyzed by comparing the relevant micropores size and the roughness of the film layer.The effects of deposition voltage and deposition time on the film layer in electrophoretic deposition were investigated and the images of microscopic morphology showed that the increase of deposition voltage in a certain range would make the morphology more uniform,while the deposition time would directly determine the denseness of the film.Microporous film layer was prepared on 3D printed Ti-6Al-4V alloy by micro-arc oxidation process.The Chitosan/Cu O/Cu₂O/reduced graphene oxide coating were prepared by electrophoretic deposition method.The excellent corrosion resistance of the coating was demonstrated by simulating the electrochemical corrosion characteristics of the film layer in a 3.5 wt%Na Cl solution.In addition,cross-sectional images and bonding charts of the films show increased denseness of the coatings while maintaining good adhesion to the substrate.Staphylococcus aureus（S.aureus）and Escherichia coli（E.Coli）were incubated in vitro at 37℃for 24 hours,and the inhibition efficiency of 98%was obtained by plate counting method.The in vitro culture experiments using mouse embryonic osteoblasts（MC3T3-E1）showed that the membrane layer was excellent in biocompatibility and showed good potential for clinical application.The Ga and Zn ion co-doped hydroxyapatite coating was prepared by electrophoretic deposition which effectively enhanced the compactness of the ceramic coating and the ratio of（Ca+Ga+Zn）/P was close to the theoretical value of hydroxyapatite（1.67）.The functional ion-doped deposited by electrophoresis effectively increased the roughness of the TC4surface from 0.024μm to 1.453μm,which is beneficial for cell proliferation culture on the coating.In addition,the contact angle of the ion-doped coating decreased continuously（from 66.4°to 15.7°）and the sustained release curve of related functional ions showed that the coating would promote the nucleation of apatite with good mineralization ability.Optical images and mathematical statistics tables of Staphylococcus aureus and Escherichia coli colonies on agar after 24 hours of in vitro culture show that the coating has high antibacterial properties that make up for the single property of hydroxyapatite.To sum up,composite coatings with micro-nano structures can be constructed by different electrolyte compositions and then using different electrical parameters,where the addition of functional elements will enhance the bioactivity of the material,as well as the mechanical properties,such as corrosion resistance,as a candidate for implants.The functional ceramic coatings prepared in this paper provide a good reference for the research value of surface modification of Ti-6Al-4V alloy.