Synergistic inhibition to dissolution corrosion by de-twinning and precipitation in alumina-forming austenitic steel exposed to lead-bismuth eutectic with 10-8 wt.% oxygen at 600°C

Abstract

This work investigated the original microstructure of cold-worked alumina-forming austenitic steel, along with its precipitation and dissolution corrosion behaviors in lead-bismuth eutectic with 10^-8 wt.% oxygen at 600°C, using solution-annealed steel for comparison. Anomalously, cold-worked steel presented milder corrosion compared to solution-annealed steel, with average corrosion depths of 314.3 and 401.0 μm after 1700 h exposure. Cold working-induced de-twinning transformed the annealing twin boundaries into normal high-angle grain boundaries (NGBs), increasing NGBs proportion from 36% to 89%. The increased NGBs provided more nucleation sites for intergranular barriers composed of alternate NiAl and M₂₃C₆ precipitates, thus better obstructing the dissolution attack.