Study On The Performance Of Al-Y Coatings And Micro-Arc Oxidation Membrane

The technology of electroplating Al–Y alloy coatings from molten salts in this thesis. In the molten salts, the influence of different contents of Y on Al–Y coatings were studied. The coatings were transformed into micro-arc oxidation coatings by the micro-arc oxidation. The impact of the Y concent in the coatings, the concentration of sodium silicate, the concentration of sodium dodecyl sulfate, the oxidation time and different kind of additive on micro-arc oxidation coatings were tested.The surface morphology, element content and the organizational structure of the Al-Y coatings and micro-arc oxidation coatings were tested by scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS) and X-ray diffraction(XRD). The corrosion resistance of the Al–Y coatings and the micro-arc oxidation coatings were analyzed by the Tafel polarization curves and electrochemical impedance spectroscopy(EIS). The thickness and the hardness of the Al–Y coatings and the micro-arc oxidation coatings were detected using the film thickness and the microhardness.The experiment results show that the addition of Y2O3 in the molten salts has a direct impact on the performance of the alloy coating. The coatings are mainly composed of aluminum and yttrium phase that are present as yttrium aluminum alloy. The micro-arc oxidation process conditions were the electrolyte sodium concentration of 10 g / L, the oxidation time of 15 min and the oxidation voltage of 350 V.The micro-arc oxidation coatings were mainly composed of Al, Fe, Al2O3 and Al3 Y. The surface uniform and density, the corrosion resistance, thickness and hardness of the Al–Y coatings and the micro-arc oxidation coatings were better than others when the Y concent was 0.56 % in the layers. The corrosion resistance of the Al–Y micro-arc oxidation coatings was improved when K2 Zr F6 and K2 Cr O4 were added to the electrolyte of sodium silicate and sodium dodecyl sulfatewere.There added K2C2O4 to the electrolyte was not effect on the corrosion resistance of the oxide film.