Characterization of residual stress and defects in welded specimen

The residual stresses developed at different locations of welded specimens consisting of austenitic Type 304L stainless steel (SS) and/or martensitic Alloy EP-823 has been characterized in terms of S-, W- and T-parameters based on a classical positron annihilation spectroscopy (PAS) technique. The resultant data indicate that the magnitude of residual stress was higher near the fusion-line (FL) compared to that of the base region of the welded specimen consisting of similar materials on both sides. However, for welded specimens of dissimilar materials on opposite side, the extent of residual stress was somewhat lower at the FL compared to that of the base region of the Alloy EP-823 side of the weld. The characterization of defects at different locations of the welded specimens by transmission electron microscopy (TEM) revealed higher dislocation density (rho) at the heat-affected-zone (HAZ) compared to that at the base material, irrespective of the weld configurations. The characterization of metallographic microstructures of tested specimens by optical microscopy exhibited larger grain size of HAZ on the Alloy EP-823 side compared to that of Type 304L SS side.