Corrosion And Wear Resistance Of Micro Arc Oxidation Ceramic Coatings On 2A50 Aluminum Alloys

Micro-arc oxidation(MAO)technology is to put the sample to be treated as anode in the electrolyte with strong electric field,its surface and solution under the action of strong voltage to produce arc discharge,produce local high temperature and high pressure,make metal atoms combine with elements in solution,and finally form a solid ceramic oxide film in situ on its surface,which can greatly improve the corrosion resistance and wear resistance of the material itself.it is mostly used in light metals such as aluminum,magnesium,titanium and their alloys,and has a good application prospect in all industrial fields.Based on a series of micro-arc oxidation experiments,a ceramic layer was formed on the surface of 2A50aluminum alloy by positive pulse power supply.scanning electron microscopy(SEM),spectrometer,x ray diffractometer(XRD),electrochemical workstation,salt spray corrosion box and multifunctional film tester were used to explore the film forming process of ceramic layer and the characterization of microstructure,phase composition,corrosion resistance and wear resistance.The main research contents are as follows:(1)Combined with the spectral information collected during the experiment,the micro-arc oxidation reaction is divided into four stages:surface oxidation stage-electric shock penetration stage-film growth stage-arc extinguishing stage.When the electrolyte concentration is low,higher current density is needed to ensure the normal reaction,but the reaction will quickly enter the growth stage of the film and extinguish the arc in a very short time.Although the film can also improve the wear resistance and corrosion resistance of2A50 aluminum alloy,the film is mainly composed of?-Al₂O₃,and the thickness of the film is only 8.2?m.(2)In order to obtain better performance,choosing a high concentration electrolyte,with a lower current density,there is a significant increase in the time of the microarc oxidation reaction,give the ceramic coating more growth time.And throughout the reaction,the frequency of the power supply plays a key role.Frequency determines unit time the number of discharges on the surface of coating,which determines the energy assigned to each discharge channel.And then affect the wear resistance and corrosion resistance of the film.(3)At 400Hz,there is a?-Al₂O₃ to?-Al₂O₃ transition in the obtained coating.And the microstructure of the film is denser,and the thickness of the film was increased to 37.8?m.At the same time,the microhardness of the film also has a significant improvement,the binding force between the ceramic layer and the matrix is also at a high level.During the grinding experiments with GCr15 steel balls in 180 minutes,it has good wear resistance.In corrosion resistance experiments,the sample of 400 Hz also showed excellent corrosion resistance.During the 240 hours simulated seawater corrosion test,2A50 protection of the coating has never failed.During the 480 hours simulated atmospheric corrosion,there is no pitting phenomenon.(4)When the power supply frequency is 400 Hz,the Mo S₂ particles are added to the film,and the wear of the film is improved well in the friction and wear experiment,and no corrosion occurs in the 480 hours simulated atmospheric corrosion experiment.