Surface Modification Research. Ta And Ag The Ion Implantation Ti6A14V Alloy

The asepsis loosing is a main problem of artificial joint or bone for long-time clinical usage, which is caused by wear and corrosion of biomaterials and so on. It will influence the service time and usage effect of artificial joint and bone. Ion implantation technique have the unique benefit in property of adhesion between film and substrate, and will not change shape and size of the substrate.So, It is a promising technique for modification of biomaterials. Ti6Al4V alloy was used widely for surgical implantation for its excellent biocompatibility and comprehensive mechanical properties. The aim of this study is to improve the wear and corrosion properties, reduce biomaterial-associated infection of Ti6Al4V alloy used in clinic. All the ion implantation experiments were carried out using metal vapour vacuum arc ion source implanter. The surface morphologies, phases structure and chemical states of Ag-ion-implanted Ti6Al4V alloy and depth profiles of Ag-ion-implanted and Ta-ion-implanted Ti6Al4V alloys at different ion doses were characterized by glancing angle X-ray diffraction, field emission scanning electron microscopy, X-ray photoelectron spectroscopy and auger electron spectroscopy. Nanoindenter instrument, multi-functional tribotester and surface profiler were used to investigate the surface hardness and tribological property of the samples. Potentiodynamic polarization technology was employed to research corrosion resistance of Ti6Al4V alloy. Ion-implanted Ti6Al4V alloy against Gram negative bacteria Escherichia coil and Gram positive bacteria Staphylococcus aureus were studied by colony forming units plate-counting method. The chemical composition, phase structure, chemical states , tribological property , corrosion resistance, antimicrobial property of Ta+Ag dual-ion-implanted Ti6Al4V were also studied systematicly in this research.Ti6Al4V alloy samples were implanted with tantalum ions at doses of 1.2×10¹⁶, 3×10¹⁶,1.5×10¹⁷,3×10¹⁷ and 4.5×10¹⁷ions/cm², respectively, with acceleration voltage of 50kV. The nano-indentation test results show that, except Ta ion dose of 3×10¹⁷ions/cm², the hardness of Ti6Al4V alloy samples was increased, the holding time of low friction coefficient increased, however, the wear of the sample didn't decrease monotony with Ta ion doses increasing. The alloy with Ta ion dose of 1.5×10¹⁷ ions/cm² has the best tribological property in this study, because whose wear was 44% decreased compared with untreated alloy. Increasing of hardness and decreasing of friction coefficient, solid-solution strengthening by Ta ion implantation of the alloys, precipitation strengthening by introduction of new Ta phase, grain boundary strengthening by grain size decreasing contribute to the tribological property improvement of Ta-ion-implanted Ti6Al4V alloy samples. The corrosion resistance of Ta-ion-implanted Ti6Al4V in Hank's solution was improved obviously due to the modified barrier layer of Ti6Al4V surface, namely, the obstruct effect of oxide layer at the outmost of the surface, the corrosion improvement effect of the solid solution alloy layer and the presence of Ta phase. The equilibrium of radiation damage and the benefit of Ta ion implantation leads to the corrosion current density of implanted alloy differ slightly from each other.Ti6Al4V alloy samples were implanted at silver ions dose of 5×10¹⁶,1×10¹⁷,5×10¹⁷,9×10¹⁷ ions/cm², respectively, with acceleration voltage of 30kV. Antibacterial test results show that antibacterial activity of Ag-ion-implanted Ti6Al4V alloy changed with implantation Ag ion dose, the antibacterial rate of Ti6Al4V alloy at Ag ion dose of 1×10¹⁷ ions/cm² obtained the highest antibacterial rate of 78% and 62% against Escherichia coil and Staphylococcus aureus. The Ag ions dissolved from titanium alloy surface, TiAg and Ag introduced during ion implantation contact with the bacterial and lead to the damage of the bacterial cell wall and cell membrane , shriving and sinking of the E.coil, which prevents the transport of essential solutes into the cell and results in leakage of proteinaceous and other intracelluar components, so provide Ag-ion-implanted Ti6Al4V alloy with antibacterial property. The corrosion resistance of Ag-ion-implanted Ti6Al4V alloy in Hank's solution was improved. The oxide layer and modified alloy layer formed in the surface of alloy prevented metal species outward and chlorine ion species inward the substrate at the same time. The excellent corrosion resistance of Ag and TiAg benefit for the corrosion resistance of the samples. The tribological property of Ag-ion-implanted Ti6Al4V alloy was also improved.The research results of Ta+Ag double-ion-implanted Ti6Al4V alloy show that its tribological property of Ta+Ag double-ion-implanted Ti6Al4V alloy was improved remarkable, the sample which was first implanted with Ag (1×10¹⁷ ions/cm²) and then Ta (1.5×10¹⁷ions/cm² ) exhibits the best wear resistance and antimicrobial property among three Ta+Ag double-ion-implanted Ti6Al4V alloy samples. The wear area of this alloy was 77% reduced and antibacterial rate against Escherichia coil and Staphylococcus aureus 72% and 60% reduced, corrosion current density 83.23% decreased compared with the unimplanted Ti6Al4V. Corrosion current of sample implanted with Ta 1.5×10¹⁷ ions/cm² at first and then Ag 1×10¹⁷ ions/cm² decreased by 94.6% compare with unimplanted Ti6Al4V alloy. The Ag ions released from the surface of dual-ion-implanted alloy, Ag, TiAg, AgO and Ag₂O produced during ion implantation contribute to the antibacterial properties of Ta+Ag dual-ion-implanted Ti6Al4V alloy samples. The obstruct layer which was composed of oxide layer, the implanted alloy layer and Ta ,Ag and TiAg produced attribute to the corrosion resistance property of Ta+Ag dual-ion-implanted Ti6Al4V alloy improving.