Environment-Induced Degradations in a Target Structural Material for Transmutation Applications

This investigation is focused on the evaluation of stress corrosion cracking (SCC) and localized corrosion behavior of Type 422 stainless steel in aqueous environments at ambient and elevated temperature. The results of constant load SCC testing using smooth specimens showed no failure in the neutral solution but a threshold stress of 97 ksi was observed in the 90°C acidic environment. SCC testing by the slow-strain-rate test method indicate that the time-to-failure, true failure stress and ductility parameters were gradually reduced with increasing temperature, showing more pronounced effect in the acidic solution. The application of a controlled cathodic potential showed further reduction in the magnitude of these parameters indicating a detrimental effect on the cracking due to hydrogen generation. The results of cyclic potentiodynamic polarization testing revealed pits and crevices on the specimen surface, showing more active (negative) critical pitting potential in the 90°C acidic solution, as expected. Metallographic and fractographic evaluations showed secondary cracks at the gage section and a combination of ductile/brittle failures at the primary fracture face, respectively