Effect of surface state on the oxidation behavior of welded 308L in simulated nominal primary water of PWR

Highlights: • A duplex oxide film can be formed on the Welded 308L. • Surface state has no influence on the phase composition of the oxide film. • Surface state can affect the thickness of the oxide film. • Surface state can affect the morphology of the oxide film. - Abstract: The oxidation behavior of 308L weld metal (WM) with different surface state in the simulated nominal primary water of pressurized water reactor (PWR) was studied by scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) analyzer and X-ray photoelectron spectroscopy (XPS). After 480 h immersion, a duplex oxide film composed of a Fe-rich outer layer (Fe₃O₄, Fe₂O₃ and a small amount of NiFe₂O₄, Ni(OH)₂, Cr(OH)₃ and (Ni, Fe)Cr₂O₄) and a Cr-rich inner layer (FeCr₂O₄ and NiCr₂O₄) can be formed on the 308L WM samples with different surface state. The surface state has no influence on the phase composition of the oxide films but obviously affects the thickness of the oxide films and the morphology of the oxides (number & size). With increasing the density of dislocations and subgrain boundaries in the cold-worked superficial layer, the thickness of the oxide film, the number and size of the oxides decrease