| Microarc oxidation (MAO) is an advanced technique of processingmaterial by means of high energy density. MAO ceramic coatings haveintensively attracted the attention of many research groups due to its desirablecharacteristics, especially the coatings on the substrates of aluminium andtitanium as well as their alloys. Recently years, the performances in all fields andapplication on the coatings fabricated by MAO have been developing andstudying by Russia and United States as well as Germany etc. in the world.However, so far, only a few research groups such as Beijing normal universityetc. have been studying the technique in our country. Because MAO is acomplicated process, which is controlled by multifactor, different technicalparameters, as-deposited MAO coatings show various properties. Moreover, theexperimental and theoretical results are not systematic or complete. Therefore,further research work on preparation and characterization of MAO films on thesubstrates of aluminium and titanium as well as their alloys, which areextensively used in many various fields, is needed. In this thesis, evaluated as anew material, MAO films on the substrates of aluminium and titanium alloys arestudied systematically in which the effect of deposited conditions on filmsproperties is investigated. It is our goal to fabricate the MAO coatings with highmicrohardness, wear durability, the lower friction coefficient, the higherelasticity, and erosion resistance as well as stable chemical property. Thecoatings on aluminium and titanium alloys are prepared by means of a self-madeindustrial frequency power supply with a real data collecting system of electricalcurrent and voltage. During experiments, the effect of basic deposited parameterson MAO coatings properties is studied, and the parameters are optimized.Simultaneously, the films with excellent properties are obtained in the optimizedexperimental conditions. On the basis of these, we have developed a novel MAOpower supply with adjustable pulse frequency and pulse width as well as theselective waveform of electrical current or voltage. And the effects of the relativeparameters on the growing properties and performances of MAO coatings onaluminium and titanium alloys are elementarily studied.This thesis consists of four parts. In the first part, ceramic coatings onaluminium alloy (LY12) are fabricated under the condition of the cathodic andanodic voltage amplitude kept at constant. During MAO process, the variationsof the cathodic and anodic current amplitude and average working current aswell as the coatings properties such as the dynamic resistance, resistance rate,surface morphology, growth rate and microhardness as well as phase componentetc. against treatment time are studied. The results show that the variations of thethree current curves with treatment time include obviously five different stagesand the variations of coatings' dynamic resistance, resistance rate and surfacemorphology as well as phase component include different stages, too. Theaverage deposition rate of films increases gradually with increased treatmenttime between 0 and 60 min, while the rate decreases with increased oxidationtime when treatment time is more than 60 min. The microhardness of thecoatings increases swiftly with increased treatment time between 0 and 45 min,and then the hardness increases slowly with increased time. The microhardnessof the film oxidized for 120 min is 2134 HV and its wear durability is better thanhorniness alloy. During deposition process, MAO coatings' dynamic positiveresistance is not equal to negative resistance and the negative resistance is greatlyless than the positive resistance in general. The oxide film consists of thesuperficial porous layer and the interior dense layer. In addition, the porous layermakes mainly up of γ-Al2O3 phase and the compact layer makes mainly up ofα-Al2O3 phase. In addition, the effects of treatment time on the coating thickness,surfac...
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