Mechanical, microstructure, and hot corrosion investigations on P22/P91 dissimilar tungsten inert gas weld

Abstract

The P22/P91 dissimilar weld increasingly used in supercritical power plan boilers calls for experimental investigations on its properties for enhanced performance in high-temperature service conditions. This study investigates the weld joint between P22/P91 steel using tungsten inert gas process employing a P22 matching filler metal. The fabricated weld has been characterized for mechanical properties of tensile strength and microhardness. The microstructural examination has been carried out in the weld region, transition zones, and base metals. The weld was exposed to a temperature of 700 °C in the environment of molten salt (50% Na2SO4 + 50% NaCl) to quantify the effect of high-temperature corrosion at its sight of application. Furthermore, the welds were also shot-peened and its effect on corrosion properties has been examined. The corroded specimens were examined using X-ray diffraction and scanning electron microscope to analyze the oxide scale produced upon exposure to high temperature in a controlled environment. The P22 base metal was found to oxidize more severely as compared to the weld fusion zone. Shot peening improves the corrosion resistance of weld by 7.56%. The results of this study comprehensively cover multiple aspects of weld integrity as per the service conditions, with its results having significant application in the power plant industry.