This paper presents the results of further microstructural evaluations of irradiated Mn-Mo-Ni wire/Linde 80 flux submerged-arc weld metals typically found in Babcock & Wilcox fabricated reactor vessels. Four Mn-Mo-Ni wire/Linde 80 surveillance weld metals were studied to characterize the size and distribution of micro-inclusions (< 0.26 μm).

Analytical TEM was used to characterize the carbides, coarse (0.1 to 2.0 μm) inclusions, and fine (2 to 50 run) precipitates. Thin foil and extraction techniques were used to characterize particle morphology while convergent beam diffraction and energy dispersive X-ray techniques were carried out to identify the crystal structural and chemical composition. The results are compared with previously evaluated unirradiated Mn-Mo-Ni wire/Linde 80 flux submerged-arc weld metals.