Evaluation of residual stresses in dissimilar weld joints

Abstract

Dissimilar metal joints between pipes of ferritic and austenitic steels are widely used in steam generators of power plants. Failure analysis carried out on a dissimilar weld joint and a literature survey have shown that a significant number of failures have occurred in the heat affected zone (HAZ) region on the ferritic steel side of such dissimilar weld joints. Residual stresses present in the weld joint are one of the main factors, which cause failures in dissimilar weld joints. A typical dissimilar pipe weld joint, representing a joint used in an Indian Fast Breeder Test Reactor (FBTR) was fabricated between 2.25Cr–1Mo ferritic steel and AISI type 316 stainless steel with and without Inconel-82 buttering on the ferritic steel side. Residual stress profiles across these weld joints were determined using the X-ray diffraction (XRD) technique. This study indicated that the Inconel-82 buttering layer employed in the dissimilar weld joint is useful in reducing the residual stresses in the HAZ of the ferritic steel and thus the buttering will be beneficial to avoid/minimize residual stress related failures of dissimilar weld joints.