Preparation And Properties In Marine Environment Of Cu-doped Micro-arc Oxidation Coatings On Titanium Alloy Surface

For their excellent comprehensive properties,titanium alloys are widely used in various fields such as aerospace and biomedicine industries.However,the poor wear resistance and marine biofouling restrict their wide application in the complex marine environment.In this thesis,the copper-doped micro arc oxidation(MAO)coatings are prepared on TC4 titanium alloy,and the influences of Cu-doping on the composition,microstructure,microhardness,wear resistance,corrosion resistance and antibacterial property of the MAO coatings have been studied with the scanning electron microscope(SEM),X-ray diffractometer(XRD),and X-ray electron spectroscopy(XPS),microhardness tester,friction-wear experiment,and antibacterial test.The conclusions are as follows:(1)The addition of copper pyrophosphate makes the color of MAO gradually change from light to dark gray,reduce the size of the surface pores and the amplitude fluctuation of the friction coefficient,enhance the density of the coatings,narrow the width of the wear scar,and significantly lower the degree of adhesion wear,but deteriorate the corrosion resistance.With the increase of copper pyrophosphate concentration,the contact angle of the MAO layer first increases and then decreases,the thickness increases,but the hardness decreases.The antibacterial test results show that the staphylococcus aureus is much likely to accumulate in the pores of the oxide layer.The addition of copper pyrophosphate greatly reduces the bacteria number on the surface of the oxide layer and the MAO coatings have the antibactericidal effect prepared with 10 g/L copper pyrophosphate concentration.(2)The addition of copper sulfate can change the color of the MAO layer from yellowish gray to dark blue and decrease the corrosion resistance.With the increase of copper sulfate concentration,the static contact angle of the MAO layer first increases and then decreases,the friction coefficient fluctuation decreases,the width of the wear scar became narrower,the surface roughness increases but the thickness did not increase obviously.When the copper sulfate concentration is 6 g/L,the oxide layer has the best uniformity and compactness with the minimum number and size of the micropores.The results of the antibacterial tests show that the addition of copper sulfate significantly reduces the number and cluster of the bacteria on the surface of the MAO layer and enhances the antibacterial property.However,with the addition of 6 g/L cuprous oxide particles,the continually increasing of the copper sulfate concentration has no obvious influence on the antibacterial property.(3)The addition of cuprous oxide makes the color of the MAO layer change from gray to yellow-brown,deteriorate the corrosion resistance,and diminish the friction coefficient fluctuation and the width of the wear scar.As the concentration of cuprous oxide increases,the thickness of the oxide layer increases and the roughness first increases and then decreases.When the amount of cuprous oxide addition is 6 g/L,the oxide layer has the best compactness with the largest contact angle and the smallest friction coefficient.The antibacterial tests show that with the increase of the concentration of cuprous oxide particles,the number of bacteria on the surface of the MAO layer decrease and the antibacterial property is gradually improved.(4)Three kinds of Cu-doping all darken the color increase the thickness and the compactness and decrease the corrosion resistance but improves the antibacterial property of the MAO layer.The self-lubricating effect of copper improves the wear performance of the MAO layer,reduces the fluctuation of the friction coefficient and narrows the width of the wear scar.