Corrosion behavior of aluminum reinforced austenitic steel in liquid lead bismuth at 550 ℃

The key material issue for the commercialization of advanced lead cooled fast reactors and accelerator driven subcritical systems is the compatibility between structural materials and lead based coolants. Structural steel materials require excellent corrosion resistance in high-temperature liquid lead bismuth eutectic (LBE) alloy. Aluminum forming austenitic steel (AFA steel) has excellent corrosion resistance in extreme environments due to its ability to form an Al₂O₃ film on its surface. However, excessively high Ni elements are more easily dissolved or oxidized in LBE than Fe and Cr elements. Therefore, this work investigates the effect of reducing Ni element composition (25-Ni steel and 18-Ni steel) on the corrosion resistance of steel in LBE. Surface treatment can protect the substrate from corrosion to some extent, so herein we explore whether it has a protective effect on AFA steel in LBE by generating Al₂O₃ through high-temperature pre oxidation. The morphology and structure of the oxide layer of AFA steel corroded for 600 h in LBE with saturated dissolved oxygen at 550 ℃ are characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), and other technologies. The results indicate that the oxide film formed after corrosion of 18-Ni steel is thinner than that after corrosion of 25-Ni steel. Performing high-temperature pre oxidation is beneficial to forming a protective Al₂O₃ oxide film on the surface of the sample, thereby reducing the thickness of the oxide layer and improving the material’s LBE corrosion resistance. The reduction in thickness of the oxide layer generated after pre oxidation of 18-Ni steel is greater than that of 25-Ni steel, so the anti-corrosion effect of 18-Ni steel after pre oxidation is better than that of 25-Ni steel.