Study On Preparation Technology And Application Of Microarc Oxidation Coating Formed On Several Aeronautical Aluminum Alloys

Functional micro-arc oxidation(MAO)coatings can extend the application of light weight and high strength aluminum alloys.In this thesis,the main purpose is to optimize the micro-arc oxidation parameters of different aluminum alloys(LY12,LY16 and LD7)substrate,and then to achieve the production application.The MAO coatings were fabricated in Na2 Si O3 based solution,and the influence of different parameters(voltage,frequency,duty cycle,oxidation time)on the growth process,discharging,microstructure and properties of coatings was studied.SEM and XRD were used to analyze the microstructure and composition of MAO coatings under different parameters.The LY12,LY16 and LD7 alloys commonly used for air plane were selected as substrates in th is work.At the same parameters,the influence of alloying elements on coating growth,discharging and microstructure were studied.The anti-corrosion properties of different MAO coatings were evaluated by salt-fog test,fungus test and wet-heat test.The results show that,the MAO coating fabricated on LY12 aluminum alloy exhibit a dense,smooth,light brown performance under specific applied parameters(550V voltage,50 min oxidation time,8% of the duty cycle and 800 Hz of the frequency).When applying the same process parameters on LY16 and LD7 aluminum alloy,it can be seen that the current density and discharge sparks intensity were enhanced with the increasing Cu content.Meanwhile,the color of the discharge sparks and coatings turn to darker with the increase of copper content.The coating became denser due to that the Mg element can inhibit pore growth and enlargement during the MAO process.The Fe content of MAO coated LD7 aluminum alloy is 0.95%,and the color of coating began to change after 800 h s alt fog test.However,the non-Fe-containing MAO coated LY12 aluminum alloy still has no any change after 1000 h,which shows that the Fe element reduces the anti-corrosion performance of coating.At the same time,the denser coating exhibits the better anti-corrosion property.According to the above process results,the optimum parameters of micro-arc oxidation on different aluminum alloy were selected.As for the complex shape of aluminum alloy such as the actuator cylinder and fairing,the specific parame ter and fixing tools of micro-arc oxidation process were designed.The properties under working condition were evaluated,and the engineering application was achieved.