Systematic Oxidation Studies of Dissimilar Ferritic/austenitic Welded Joints

A comparative analysis of different zones of T91/347 H, GTAW dissimilar welded joint exposed to simulated boiler conditions has been attempted. T91 HAZ region of the ferritic/austenitic dissimilar welding joint has been observed to develop higher oxide scale than other parts of joint by virtue of its higher oxidation. Material characterisation in as welded as well as in as corroded conditions was done with the help of optical microscopy, SEM/EDS, compositional mapping, XRD and weight change tests. The characterisation study has corroborated lower presence of oxidation resistant Cr in HAZ of T91 due to availability of chromium carbides, delta ferrites, intermetallics as well as martensitic structure in as welded studies. This in turn has propelled the T91HAZ region to have weak oxidation resistance. T91 HAZ has shown highest oxidation than other regions of the weldment due to low intensity of protective phases as well as more presence of Fe2O3 phase.