EFFECT OF CURRENT INTENSITY ON THE PROPERTIES OF CERAMIC COATINGS FABRICATED BY MICRO-ARC OXIDATION

Ceramic coatings have been synthesized on 6063 aluminum alloy by micro-arc oxidation (MAO) technique. The effects of current intensity on the chemical and mechanical properties of MAO coatings have been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), micro-hardness test, adhesion measurement, and friction and wear tests. The fabricated samples consist mainly of α-Al2O3 and γ-Al2O3 phases. SEM results show that the surface of the prepared coatings is dense except some pores distributed over the coating surface. Mechanical measurements show that these kinds of samples have high hardness, excellent adhesion, and high friction resistance. The coating consists of a thin buffer layer at the metal surface followed by a relatively compact inner layer and finally a higher porous ceramic layer. Meanwhile, there is a nonuniform distribution of hardness for the samples in the plane parallel to the substrate.