Corrosion behavior of electron beam welded 9Cr ferritic/martensitic steel in a liquid lead–bismuth eutectic at 550 °C

The corrosion resistance of welded joints in a lead–bismuth eutectic (LBE) environment is crucial for the development of lead-cooled fast reactors (LFRs), as the welded joints typically exhibit more severe corrosion damage than the base material (BM). This study employed multiscale characterization techniques to analyze the microstructure of the oxide scale on a 9Cr ferritic/martensitic (F/M) steel electron beam welded (EBW) joint exposed to a LBE environment at 550 °C, with an oxygen concentration of 1.5 × 10−6 wt% for 2040 h. The results revealed that the thickness of the corrosion oxide scale in the fusion zone (FZ) is greater than that in the heat-affected zone (HAZ) and the BM, with the inner oxide zone (IOZ) being particularly pronounced. Based on the microstructural characteristics of different regions of the EBW joint, the reasons for the accelerated growth of the oxide scale in the FZ were discussed. Additionally, the influence of the typical microstructural features of 9Cr F/M steel on corrosion behavior in liquid LBE were explored in depth. These findings provide new insights into the corrosion behavior of EBW joints in liquid LBE environments.