Preparation And Characterization Of Ti-doped DLC Coating On AZ31 Magnesium Alloys

Medical magnesium alloy has similar mechanical properties to human bone tissue,and because of its easy degradation in the body environment,it has potential clinical application in fracture fixation.However,due to the active chemical properties of magnesium alloy,especially in the human environment with chloride ions,it is very easy to corrosion,resulting in the non healing of tissue and degradation of implant materials.Therefore,if magnesium alloy is to be used in clinic,the first problem is to solve the problem of poor corrosion resistance.Objective:to sputter Ti doped DLC coating on the surface of medical AZ31system magnesium alloy to improve the corrosion resistance of magnesium alloy,and to explore its biocompatibility.Methods:A microporous oxidation method was used to prepare a porous porous oxide ceramic coating on the surface of medical AZ31 magnesium alloy,and then a titanium-doped DLC coating was prepared on the surface of the oxide ceramic coating by magnetron sputtering.Field emission scanning electron microscopy（SEM）,Raman spectroscopy（Raman）,atomic force microscope（AFM）and energy dispersive X-ray spectrometer（EDS）were used to characterize the samples.The measurement of the corrosion resistance of the sample was completed by the hydrogen collection experiment and the kinetic potential polarization curve test.At the same time,the MTT method and the cell morphology observation method were used to complete the sample cell compatibility evaluation.Results:In this experiment,titanium-doped MAO/DLC coating was successfully prepared on the surface of AZ31 magnesium alloy.The surface of the coating was uniform and the phenomenon of plugging occurred.The coating was well bonded to the base metal with a thickness of about 15μm.The corrosion resistance results show that the corrosion potential of the titanium-doped MAO/DLC group is-1.359±0.026V vs.Ag/Ag Cl,and the corrosion current density value is（1.248±0.341）×10^-7A/cm²,compared with AZ31 magnesium alloy,The corrosion potential increased by 35mV,and the corrosion current density decreased by about 100 times.The hydrogen evolution experiment shows that the hydrogen release rate of MAO/DLC group is lower,indicating that the corrosion resistance of modified magnesium alloy is improved.The evaluation of CCK-8 cytotoxicity results showed that the relative increase rate of cells in the titanium-doped MAO/DLC group was higher than100%,and the cell morphology of the cultured extracts of the titanium-doped MAO/DLC group was similar to that of the control group under an inverted microscope.The number was larger than that of the control group,indicating that titanium-doped MAO/DLC had no cytotoxicity and could promote cell proliferation.Conclusion:In this experiment,a titanium-doped MAO/DLC coating was successfully prepared on the surface of medical AZ31 magnesium alloy,and the corrosion resistance and cell compatibility of the modified AZ31 magnesium alloy were significantly improved.This is because the magnesium alloy is degradable The application in the field of medical materials provides a theoretical basis.