Study of Oxide Film Formed in a Pre Cracked CT Specimen of AISI 304L During a Rising Displacement Test in 288°C Water

ABSTRACT

Study of oxide film formed inside the pre crack in a CT specimens during a rising displacement test in high temperature water (288°C), under environments used in Boiling Water Reactor (BWR): Normal Water Condition (NWC – 200 ppb O₂) and Hydrogen Water Chemistry (HWC – 125 ppb H₂), was realized by scanning electron microscopy (SEM), and X-ray diffraction (XRD). In both cases the oxide film consisted of two layers and was identify as magnetite. In the case of HWC this results are agree with previous reports that mentioned to magnetite as stable phase in reducing conditions; however the presence of magnetite crystals in NWC has not been reported due to the stable phase in oxidant conditions is hematite. This situation permit infer that inside the pre crack of CT specimens the environmental conditions was different with the oxidant bulk, and probably a poor oxygen access and stagnant conditions within the narrow crack, promoted a localized reducing environment that permitted the magnetite formation. Is evident that the crack growth studies should be considered the conditions inside crack because is significantly different.