Research Of New Type Aluminum Alloy Ceramic Film Preparation And Properties

Micro arc oxidation,as an excellent surface treatment method,which is popular with valve metals such as aluminum,magnesium and titanium.Now,it is limited by the high electric energy and the corrosion of surface pores.Aluminum alloy was developed in Na₂Si O₃-KOH electrolyte system from the surface of 2A12.By using micro arc oxidation with pulse power supply.The micro-arc oxidation（MAO）films were prepared at low voltage by adding additive Na F and step-by-step voltage increasing method;the slow-release micro arc oxidation film was prepared by adding rare earth oxide Ce O₂;the high-temperature resistance of MAO film was studied under high-temperature.In the experiment,the structure,surface appearance,corrosion resistance of the samples was characterized by SEM、XRD、EDS and electrochemical workstation,respectively.The results show that Na F can effectively reduce the voltage required by micro-arc oxidation,and can react when the forward voltage is 220V.The main components of the film are Al、Si、O,and the main phase structure areα-Al₂O₃and amorphous Al₂O₃.The corrosion resistance is good when the voltage is 300V,the number of boost sections is 4,the boost rate is 10V/min,the concentration of Na F is 1g/L,and the reaction time is 30min.With the addition of rare earth oxide corrosion inhibitor Ce O₂,the crater like pores on the surface of micro arc oxidation film appear obvious self-sealing phenomenon.Ce O₂ not only participates in the micro arc oxidation reaction,but also adsorbs in the crater like holes on the surface of the slow-release micro arc oxidation film.The composition of the film is mainly composed of Al、O、Si and Ce.The corrosion resistance is the best when the reaction time is 19min,the forward voltage is 300V and the concentration of Ce O₂ is 3g/L.The slow-release micro arc oxidation coating can effectively play a protective role in the first 60 minutes of cavitation reaction.When enhance the heating temperature,the resistance to high temperature oxidation of MAO film decreases with the increase of temperature,but the oxidation index is more than 2.It can be conclude that MAO film keeps the inside surface from the external environment in high temperature oxidation experiment and prevents the diffusion of O effectively.In the study,it also illustrate that the thermal shock resistance of MAO film in the air is better than water cooling.Under 60 thermal shock cycles,the film shedding phenomenon appears at the corner of the water cooling thermal shock group,while the air cooling thermal shock group only has cracks on the surface,and there is no film falling off phenomenon.Ce O₂ can effectively reduce the effect of thermal shock on the film at the initial stage of thermal shock reaction.However,with the increase of the number of cycles,alkali carbonate and hydroxide will be formed,resulting in failure.