Corrosion behaviour of detonation gun sprayed cermet coatings on AA5083

Abstract

Cermet coatings were fabricated on AA5083 by D gun coating technique using three different combinations of powder feedstock namely WC–Co, WC–Co–Cr, and Cr₃C₂–NiCr. The effect of powder combinations on coatings’ phase composition, surface morphology, and cross-sectional microstructure were investigated using XRD, SEM, and EDS. Major findings revealed that WC–Co and WC–Co–Cr powders produced higher thickness with considerable surface defects compared to a coating that was produced by Cr₃C₂–NiCr powders. Moreover, a smooth compact and a uniform coating was obtained by using Cr₃C₂–NiCr powders. Electrochemical corrosion results showed that the OCP values of all the coated samples were shifted to a higher value than substrate and sample coated with Cr₃C₂–NiCr powder showed a stable OCP and more positive value than other coated samples. Similarly, the PDP curve of sample coated with Cr₃C₂–NiCr also showed lower corrosion current density at the cathodic region and better passivation behaviour in the anodic region.