Corrosion fatigue behavior of an alloy 52-A508 weldment and low alloy steels under simulated BWR coolant conditions

The corrosion fatigue crack growth behavior of A533, A508 low alloy steels and Inconel Alloy 52-A508 weldment under simulated BWR coolant conditions was studied. Corrosion fatigue crack growth rates of the dissimilar metal weldments were observed to increase with crack extension under the nominally constant ΔK loading mode. It can be accounted for by an increase in the tensile residual stress and a decrease in the crack closure effect with the weld depth. Corrosion fatigue crack growth rates of A533B3 and A508 cl. 3 steels were significantly affected by the steel sulfur content, loading frequency and dissolved oxygen content of the water coolant. When the steel sulfur content was decreased to a critical sulfur content, 0.005 wt%, the crack growth rates decreased remarkably. At the same sulfur level, the corrosion fatigue crack growth rates were comparable for the steel specimens in different orientations, which could be related to the rates of exposure of fresh sulfide to the water environment. By a rough estimate, the percentage of sulfides per unit fracture surface was equivalent for the steel specimens of both orientations. (author)