Alloys Comparative Study on Microstructure and Corrosion Resistance of Alumina Coats on Al۲۰۲۴ and Al۶۰۶۱alloys Coated by Plasma Electrolytic Oxidation Technique

In this study, alumina was coated on Al۲۰۲۴ and Al۶۰۶۱ using plasma electrolytic oxidation method and the effects of Al substrate and applied voltage on the properties of coated samples were investigated. Scanning electron microscopy and X-ray diffraction were used to study the microstructure of coated samples and microhardness and corrosion tests were employed to evaluate the final properties of the coats. The results showed that with increase of applied voltage, α-alumina increased in the coats of both alloys however it enhanced more moderately for Al۲۰۲۴. Generally, the amount of α-alumina in Al۲۰۲۴ specimens was less than that of Al۶۰۶۱. The presence of more alloying elements in Al۲۰۲۴ led to the more metallic ions in its coat preventing the gammato-alpha alumina transition. Moreover, the highest corrosion resistance belongs to the Al۲۰۲۴ coated by ۴۰۰ V and the Al۶۰۶۱ coated by ۴۲۵ V and the corrosion potential values for them were measured -۰.۵۷۱ V and -۰.۵۴۹ V, respectively. The corrosion test also indicated that ۶۷-۶۸% α-alumina in the coatings can lead to the highest corrosion resistance. The microhardness test indicated that the maximum hardness value belongs to the samples coated by ۴۵۰ V so that the values for the Al۲۰۲۴ and Al۶۰۶۱ coats were ۱۳۶۰ and ۱۴۷۵ Vickers, respectively.

کلیدواژه ها:

plasma electrolytic oxidation ، aluminum ، corrosion ، α-Al۲O۳ ، γ-Al۲O۳ ، کلمات کلیدی: اکسیداسیون الکترولیتی پلاسما ، آلومینیوم ، خوردگی ، α-Al۲O۳ ، γ-Al۲O۳