Cavitation erosion and its effect on corrosion resistance of nuclear-grade Z3CN20–09M stainless steel

Abstract

Z3CN20–09M stainless steel, a candidate material for coolant pump shells, experiences cavitation erosion (CE) in nuclear reactor service. Z3CN20–09M steel's CE behavior is studied using scanning electron microscopy, transmission electron microscopy, electron back-scatter diffraction, and optical profilometry. The influence of CE on corrosion resistance is analyzed through potentiodynamic polarization tests and time-of-flight secondary ion mass spectrometry. During the incubation stage, damage occurs primarily in austenite. A higher Taylor factor increases the CE. Slip bands and strain-induced martensite are the main reasons for damage. After the incubation stage, brittle ferrite fracture dominates, which induces large grooves and holes. One hour of exposure improves the corrosion resistance. Slip bands, strain-induced martensite, and stacking faults provide diffusion paths for the Cr and O atoms to form a more compact passive film. Finally, approaches aiming to improve the CE resistance of Z3CN20–09M steel are suggested.