Microstructure and Micro-Hardness of Dissimilar Metal Cladding from a Pipe-Nozzle Mockup for PWR

In this study, the dissimilar metal cladding from a pressure vessel pipe-nozzle mockup for PWR was studied using an optical microscope, scanning electron microscopy, energy-dispersive X-ray spectrometry, electron back-scattering diffraction, and micro-hardness measurement. The microstructure of the SA508 side is non-uniform along the fusion boundary, especially at the concave and convex areas. Martensitic layer (type I and type II) boundaries are found at the fusion boundary area. The chemical composition, residual strain, and microstructure across the SA508-309L fusion boundary are very complex and hence result in a complicated micro-hardness distribution.