The effect of applied voltage on physical and chemical properties of ZrO2-Al2O3 ceramic coatings via micro arc oxidation

Aluminum alloys are one of the most attractive materials due to their high specific strength, low density, and very abundance reserves in the earth’s crust.Aerospace, automobile, building, and so on are some of the industrial fields where aluminum and its alloys are utilized. However, it has some disadvantages, namely softness, lower wear resistance and lower corrosion resistance, decreases the service life of machine components. An effective approach to defeat these above disadvantages is coating the aluminum components with alumina-based composites coatings. Among alumina-based composites coatings, Al2O3-ZrO2 system has demonstrated unique features. Micro Arc oxidation(MAO) technique was employed to grow zirconia–alumina porous layers. The layers were grown under alternative current in the electrolytes of ZrOCl2 salt. Considering XPS,XRD, and EDX results, the layers mainly consisted of a-Al2O3, γ-Al2O3, monoclinic ZrO2, tetragonal ZrO2. Increasing the voltage resulted in higher zirconium concentration. AFM studies revealed that the surface roughness increased with voltage. Morphological evaluations, performed by SEM, showed that the microstructure of the layers strongly depended on the applied voltage.