Role of Cavity Formation in Crack Initiation of Cold-Worked Carbon Steel in High-Temperature Water

Crack initiation behavior was studied to understand the underlying processes during the incubation period for prediction of crack initiation after long-term exposure in high-temperature water. Tests were performed using blunt-notched compact tension-type specimens of cold-worked carbon steel (ASTM A106 [UNS K03006]) exposed under static load condition in hydrogenated pure water and in air in the range of temperatures between 320°C and 450°C. Five important patterns were observed. First, intergranular cracking was observed in both water and air, even in static load conditions when steel specimens had been cold-worked. Second, 1/T-type temperature dependencies of initiation times were observed for cold-worked (CW) carbon steel (CW carbon steel), and the crack initiation time in an operating plant (Point Lepreau Nuclear Generating Station, Point Lepreau, New Brunswick, Canada) seemed to lie in the extrapolated line of the experimental results. Third, cavities were identified at the grain boundaries at the bo...