| In order to improve the corrosion resistance of medical Mg-Zn-Zr-Sr alloy and meet the requirements of clinical use of bone implant materials.In this paper,a micro-arc oxidation ceramic coating was prepared on the surface of Mg-Zn-Zr-Sr alloy in an phosphate electrolyte system electrolyte,and the process parameters of micro-arc oxidation?MAO?are optimized by system.In order to further enhance the protection performance of micro-arc oxidation coating,a dense whisker like fluorine hydroxyapatite coating was prepared on the surface of micro-arc oxidation coatings by water bath method.The corrosion resistance and the in vitro mineralization ability of micro-arc oxidation samples and fluorine hydroxyapatite coated micro-arc oxidation samples after optimizing the process parameters were discussed.The results are listed as follows:1.Under the condition that the rest of the parameters are determined,with the increase of positive voltage of micro-arc oxidation,the coatings layer thickness of Mg-Zn-Zr-Sr alloy increased gradually,the composition phase were MgO and Mg3?PO4?2,the size of the surface pores increased and the number of pores decreased,the corrosion resistance of the films is best when the positive voltage is 400 V;With the increase of pulse frequency,the number of pores increases,the pore size decreases,and the thickness of films changes little,when the pulse frequency is 600 Hz,the corrosion resistance of coatings is the best;With the increase of the positive duty ratio of the power supply,the film gradually thickens,the film is denser when the positive duty ratio is 30%,and the corrosion resistance is the best at this time.2.With the prolonging of the heating time of the water bath,the Ca-P compounds on the surface of the MAO films gradually nucleated and grown.After the water bath is heated for30 min,a compact coating?MAO30?consisting of a 100nm diameter rod like fluorapatite was formed on the surface of the micro arc oxidation film,and the thickness was about 6?m.The corrosion resistance of MAO coated Mg-Zn-Zr-Sr alloy is further improved,and have relatively high corrosion potential?-1.19 V?and low corrosion current density(6.27×10-7A/cm2).3.Compared with MAO coating,MAO30 has a more compact structure.When soaking in simulated body fluid at 37?,the pH value of MAO30 soaking solution has little change,the weight loss of the sample is smaller,and the surface macroscopic morphology is more complete.After immersed in SBF for 7 days,the mineralization layer of MAO30 samples is composed of needle shaped clusters of HA structure that the diameter is 100 nm,after immersed for 20 days,the thickness of HA mineralization layer reached about 20 m and fused with the original coating.MAO30 samples showed a good ability to induce hydroxyapatite deposition. |
PDF Full Text Request