Erosion-corrosion behaviors of P91 steel in high flowing lead-bismuth eutectic (LBE)

Based on the development and demand of Generation IV nuclear energy systems, the lead-cooled fast reactor (LFR) is one of the six main reactor types to be developed in the next step. And the liquid lead-bismuth eutectic (LBE) was used as the coolant in the LFR. However, under the condition of high temperature and high flow rate, erosion corrosion wear between LBE and structural materials severely limits its application. In this study, P91 steel was exposed to high flowing LBE (5 m/s) for up to 3000 h at 350 ℃ and 450 ℃, respectively. It was found that the oxide layer formed on the surface of P91 steel at 350 °C is a multi-layer structure: loose Fe3O4 layer, Fe-Cr spinel layer and inner oxidation zone from outside to inside. After 3000 h, the substrate was not eroded by LBE, and the oxide scale experienced a dynamic equilibrium process of "spalling - regeneration". When the temperature reaches 450 °C, the overall oxidative corrosion phenomenon is more serious. The characteristics of the different LBE incident angles are discrepancy. After 3000 h, the severity of damage caused by LBE incident angle is as follows: 30° > 90° > -90°. At 30°, the oxide layer completely spall off and LBE penetrated into the substrate. At 90°, the oxide layer was partially peeled off, but the matrix was not eroded by LBE. At -90°, the oxide layer remained intact. This study reveals the erosion-corrosion behaviors of P91 steel in high flowing (5 m/s) LBE, and elucidates the formation and spalling mechanism of the oxide layer, which can provide reference for the material loss mechanism and research and development of LFR of the Generation IV nuclear energy systems.