Monitoring of stress corrosion cracking of duplex stainless steel by electrochemical potential noise and load signal in simulated pressurised water reactor primary water

Abstract

A duplex stainless steel with a significant Si content was exposed to a constant elongation rate tensile test in simulated pressurised water reactor (PWR) primary water at 300°C. Simultaneously, electrochemical potential noise was measured between the tensile specimen and a Pt wire. A reference test was conducted in dry Ar under identical conditions to assess the contribution of stress corrosion cracking. In PWR water, fracture was predominantly transgranular with minimal ductile deformation, and time to failure was shorter compared to dry Ar, where the fully ductile fracture occurred. Secondary cracks in PWR water were small and initiated at machining marks. No transients in load or potential noise were detected before yielding in either environment, suggesting SCC initiation requires plastic deformation. After yielding, predominantly simultaneous transients in both signals were observed in PWR water, indicating stress corrosion cracking propagation as the primary failure mechanism. A linear relationship between magnitudes of these transients was identified shortly before fracture. The findings demonstrate that the propagation of transgranular cleavage cracking serves as the primary mechanism of failure in PWR water. Additionally, they highlight the significant role of signal analysis from multiple sources in the detection of stress corrosion cracking within challenging environments.