Local Mechanical Properties and Microstructures of Alloy52M Dissimilar Metal Welded Joint between A508 Ferritic Steel and 316L Stainless Steel

Abstract

The local mechanical properties and microstructures in a real dissimilar metal welded joint (DMWJ) of nuclear power plant were investigated. Results show that the distributions of mechanical properties in the DMWJ are very inhomogeneous. Especially in the three interface regions of A508/Alloy52Mb, Alloy52Mb/Alloy52Mw and Alloy52Mw/316L, the inhomogeneous characteristics are most prominent, and some local softening and hardening zones are formed. This non-uniform distribution on mechanical properties is mainly caused by the different microstructures in the DMWJ. The local dramatic variations in mechanical properties and local mismatch effect in the softening and hardening zones have significant effects on macroscopic fracture mechanics parameter, local crack initiation and growth behavior. But they are not considered in present structure integrity assessment codes and Leak-Before-Break (LBB) analysis. For assessing integrity and conducting LBB analysis on the DMWJ accurately, it is necessary to determine the local mechanical properties and their local mismatch ratios. In addition, the new integrity assessment and LBB analysis methods based on local damage and fracture need to be developed.