High temperature molten salt corrosion investigations on P22/P91 power plant dissimilar welds

Abstract

This article investigates the hot corrosion behavior of P22/P91 dissimilar welds used in power plant applications. The hot corrosion behavior of P22/P91 dissimilar welds was observed under the exposure of molten salts Na2SO4 + 60% V2O5 (SM1) and Na2SO4 + 50% NaCl (SM2) at the temperature of 650°C and 750°C. The welds were fabricated by shielded metal arc welding (SMAW) process using the laboratory developed electrode. This study is an attempt to develop welding electrodes which provide better mechanical and hot corrosion properties as compared to the commercially available electrodes for joining P22/P91 alloys. Thermogravimetric analysis was used to study the oxidation kinetics. XRD, SEM/EDS characterization has been performed to analyze the oxide scale morphology. Results obtained indicate that the welds exposed to SM2 gain more weight as compared to that of SM1. A significant gain in weight was observed with an increase in the exposure temperature. Dissimilar welds fabricated using laboratory-made electrodes (CM1, CM2) show enhanced corrosion resistance in all the exposed environments.