Tensile Properties Variation Across the Dissimilar Metal Weld Joint Between Modified 9Cr–1Mo Ferritic Steel and 316LN Stainless Steel at RT and 550 °C

Abstract

In liquid metal cooled fast breeder reactors (LMFBR), modified 9Cr–1Mo ferritic steel (P91 or Grade 91) is a preferred material for constructing steam generators due to its creep strength and stress corrosion cracking resistance. The austenitic stainless steels (SS 316LN and SS 304LN) are widely used for primary and secondary piping systems because of its oxidation resistance and excellent creep strength. So, the dissimilar metal weld joint (DMWJ) between P91 and SS 316LN is inevitable. Nickel-based consumables (Alloy 82 and Alloy 182) are preferred to join these materials. The DMWJ will experience the temperature up to 550 °C. For accurate integrity assessment, the mechanical properties of individual regions are to be evaluated at room temperature (RT) and 550 °C. Hence, the present investigation is focused on evaluating the mechanical properties of various regions of DMWJ at RT and 550 °C. From this investigation, it is understood that the tensile properties are heterogeneous across the DMWJ at RT and 550 °C. The high-temperature (550 °C) tensile properties are significantly lower with respect to the RT properties. The development of complex microstructures at the interfaces will alter the mechanical properties across the DMWJ.