EXPERIMENTAL INVESTIGATION ON DISSIMILAR WELDING OF MSS TO ASS FOR POWER PLANT APPLICATION

Abstract

Austenitic stainless steels (ASS) are widely used in industries due to their excellent corrosion resistance and mechanical
properties. Traditionally, nickel (Ni) is the key alloying element that stabilizes the austenitic phase in stainless steels, but recent trends are shifting towards the use of reduced nickel content. Manganese (Mn) and nitrogen (N) have emerged as replacements for nickel, leading to the development of austenitic grades like the 200 series, particularly grade 202, which offers high hardness, strength, and corrosion resistance at a reduced cost. However, the sustainability of austenitic steels, especially in aggressive environments, remains a challenge. Duplex stainless steels (DSS), which combine ferritic and austenitic phases, may offer a cost-effective alternative with improved properties. This review explores the challenges of dissimilar welding between martensitic P91/P92 steel and austenitic stainless steel, focusing on their application in Ultra Super Critical (USC) power plants. The review covers the mechanical behavior, microstructural issues, and weldability challenges such as hot cracking, carbon migration, and formation of brittle intermetallic compounds. The role of filler metals, post-weld heat treatment (PWHT), and the effects of precipitate coarsening are also discussed. Finally, the potential for composite welds combining duplex and austenitic steels is highlighted for improved strength and corrosion resistance, offering new opportunities in high-performance applications.