Micro-arc Oxidation Process And Biocompatibility Research Of TLM Medical Titanium Allo

Titanium and its alloys are widely used as bio-implant materials due to their excellent mechanical properties and biocompatibility.However,the poor biological activity and wear resistance of titanium and its alloys limit their further applications.Therefore,it is necessary to further optimize the surface of titanium and its alloy.In this paper,the micro-arc oxidation process(MAO)was used to prepare a coating containing calcium and phosphorus on the surface of the elastic modulus of Ti-3Zr-2Sn-3Mo-25Nb(TLM)titanium alloy.Under the phosphate electrolyte system,an orthogonal test was used to study the influence of the four factors of Ca/P ratio,oxidation time,current density,and duty cycle on the hardness thickness and roughness of the coating,thereby determining the optimal micro-arc oxidation process.Under the best process parameters,the effects of sodium fluoride additives on the basic properties of the coating thickness,hardness,roughness,binding force,morphology,phase composition,etc.were studied.In addition,through the simulated body fluid(SBF)in vitro immersion experiment,the effects of sodium fluoride additives on the morphology and phase composition,corrosion resistance,wettability,and clotting time of the coating after immersion were analyzed.It can be seen from the orthogonal test that the optimal process parameters of TLM titanium alloy micro-arc oxidation in this work are:Ca/P ratio is 3.67,oxidation time is 30min,current density is 8A/dm2,and duty ratio is 40%.Under the best process parameters,the effects of sodium fluoride additives on the basic properties of the coating thickness,hardness,roughness,binding force,morphology,phase composition,etc.were studied.The studies have shown that with the increase of NaF concentration,the oxidation voltage and the coating thickness are increasing,while the coating hardness,surface roughness,and binding force are increasing first and then decreasing.When the NaF concentration is 3.0g/L,the comprehensive performance of the coating is optimal.The micro-arc oxidation coating is mainly composed of four elements:O,Ti,Ca,P,and F.The phases of the coating are mainly rutile TiO2,anatase TiO2,CaTiO3 and matrix titanium.In addition,through the simulated body fluid in vitro immersion experiment,the effects of sodium fluoride additives on the morphology and phase composition,corrosion resistance,wettability,and clotting time of the coating after immersion were analyzed.The studies have shown that after immersion in simulated body fluids,white granular hydroxyapatite is formed on the surface of the coating,but as the amount of NaF added and the immersion time increases,the white spherical particles of the micro-arc oxidation coating partially dissolve.When the amount of NaF added is 3.0g/L,the coating has the most excellent corrosion resistance.As the content of NaF increases,the contact angle on the surface of the coating decreases first and then increases.When the amount of NaF added is 3.0g/L,the wettability of the coating is best.As the NaF content increases,the absorbance of the titanium alloy increases first and then decreases.When the amount of NaF added is 3.0g/L,the absorbance of the titanium alloy reaches a maximum of 0.3.When the concentration of sodium fluoride is 2.0g/L and 3.0g/L,the increase of quality of the coating is large,which tends to increase first and then decrease.In the first 10 days after the coating immersed in the simulated body fluid,the PH value in the simulated body fluid generally showed an upward trend;while in the 8 days after the immersion,the pH value in the simulated body fluid generally showed a downward trend,which may be due to the arc-oxidation coating growing by absorbing Ca2+and HPO42-in the simulated body fluid,so that the pH value in the simulated body fluid decreases.