Exploring the Weldability of Austenitic Stainless Steels in Advanced Ultra-Supercritical Power Plant Applications: An Extensive Review

Despite continuous efforts to enhance the operational efficiency of power plants dependent on these fuels, fossil fuels are expected to remain a significant global energy source in the coming decades. India has initiated a mission program to establish Advanced Ultra Super Critical (AUSC) power plants operating at temperature and pressure exceeding 720°C and 30.4kPa respectively. These plants are anticipated to utilize specialized materials with high resistance to corrosion and deformation at elevated temperatures. Among the materials considered, Nickel-base alloys, Creep Strength Enhanced Ferritic (CSEF) Steels and Austenitic Stainless Steels have emerged as the primary candidates. The prime emphasis of this paper is directed towards examining the weldability of Austenitic Stainless Steels utilized in AUSC power plants. It encompasses various aspects such as the choice of filler materials, welding techniques, and the attributes of welds involving both similar and dissimilar metals. The paper provides a comprehensive review of weldability challenges encountered in Austenitic Stainless Steels, including issues like liquation cracking in the heat-affected zone (HAZ), hot cracking, and stress relaxation cracking induced by tramp elements. Additionally, it investigates the performance of different filler wires, namely ER304HCu, ERNiCrCoMo-1, and ERNiCrMo-3, in weld joints involving 304HCu SS tubes, as well as ERNiCrCoMo-1 in dissimilar tube weld joints between 304HCu Stainless Steel and Alloy 617M.