The intergranular oxidation susceptibility of thermally-treated Alloy 600

The oxidation behaviour of thermally-treated Alloy 600 was studied in hydrogenated steam at 480 °C, an environment used to accelerate the oxidation reactions observed under pressurized water reactors conditions. Focused ion beam (FIB) and analytical transmission electron microscopy (ATEM) provided direct evidence of localized intergranular carbide decomposition and the formation of an intergranular Cr-rich oxide embryo. These results are in terms of the early stages of preferential intergranular oxidation and the role of carbides on grain boundary migration, carbide decomposition, and the effect of local carbon enrichments in the matrix.