Characterization of Coating Formed on Pure Zirconium by MAO in Yttrium Acetate Tetrahydrate Containing Electrolyte

Abstract

In this study, oxide coatings were produced on pure zirconium by micro arc oxidation method in the electrolytes containing sodium silicate and different amounts of yttrium acetate tetrahydrate (1-4 g/l) for the same coating duration of 1 h. The surface roughness, microstructure, phase content and chemical composition of the coatings were characterized by using scanning electron microscopy, profilometry and X-Ray diffractometry. It was found that the surfaces of coatings on zirconium consist of monoclinic-ZrO<inf>2</inf>, tetragonal-ZrO<inf>2</inf> phases. The coating thickness decreases with addition of yttrium acetate tetrahydrate while it does not change significantly with the increase of its amount. The clustered equiaxed features were formed on the surfaces of the coatings. As the amount of yttrium acetate tetrahydrate in the electrolyte solution increased, the coating/substrate interface smoothened. Two main regions of the coating, the outer dense region (I) and the porous inner region (II), became significant with addition of YAT into the electrolyte.