Research On The Formation And Mechanism Of Ceramic Coating Prepared By Micro-Arc Oxidation On Surface Of Aluminum Alloy

Micro-arc oxidation (MAO) also prefered to as micro plasma oxidation or anode spark deposition, is a new complex plasma-discharge process, involving electrochemical, plasma chemical, and thermochemical processes, which is used to produce ceramic film in situs on the surface of valve metal or their alloy's. The coatings prepared by this process have excellent performances in terms of adhesion, hardness, friction, corrosion-resistance and dielectric properties. This technique adopts an advanced heating up method employing micro-plasma with ultra high energy density, and does not affect the structure of substrate; it is not a difficult process and does not induce environmental pollution as well. At present, Russia takes the lead not only in academic research but also in application. This technology also draws close attention of western countries. China has developed this technique in recent years.Micro-arc oxidation is a compelx process, which involves electrochemical chemical, optical, electrical and thermal processes. It is combined with the formation of oxide film formed by electro-chemistry and the following breakdown of ceramic coating, and influenced by parameters of substrates, power supply and electrolyte. It is too complex to inspect online, so there is no academic model that can explain various experiment phenomena. Research on mechanism should be conducted further and perfectly.In this dissertation, the mechanism of MAO, technical regularity, technical experiments and the characteristics of MAO coating were studied systemically for the purpose of the grasp, further research and industrialization of this technology.Formation mechanism is a theoretical foundation of MAO process. So at first the mechanism of MAO was analyzed, and the mechanism and academic model of MAO was also studied. The result shows that in discharge channel the temperature of electron (Te) is equal to that of gas (Tg), because electron can't be accelerated enough under the high pressure in the channel, and the energy was absorbed as heat efficiently through collision.The plasma produced in MAO process is mainly consisted of oxygen. The oxygen bubble in the hole was firstly broke down, and the oxygen plasma is produced. The ceramic coating was broke down by the joule heat and free electron...