Possibility of detection of crack initiation in high temperature water

The initiation of stress corrosion cracks in sensitised austenitic stainless steel under high temperature water conditions (simulated boiling water reactor environment) was detected, applying electrochemical noise measurement technique. The stress corrosion cracks were generated on pre-oxidised, unnotched standard tensile round bar specimens under constant load conditions. The elementary transients associated with stress corrosion crack initiation were found to be embedded in the basic noise pattern coming from the oxide growth reaction on the tensile specimen. Thus a simple calculation of standard deviations to identify localised corrosion phenomena under high temperature water conditions cannot be used. The changes in the track of power density spectra proved to be much more suitable to indicate stress corrosion crack initiation under high temperature water conditions.