AlOx-enriched surface tailoring of FeCrAlY coating for compact oxide-scale formation and enhanced interfacial stability in liquid lead-bismuth eutectic

FeCrAlY coatings are promising protective materials for structural components in lead-cooled fast reactors, but their long-term performance in lead-bismuth eutectic (LBE) is often limited by insufficient oxide-scale stability and degradation of coating/substrate adhesion. In this work, a ∼0.3 μm AlO x -enriched surface layer was deposited on magnetron-sputtered FeCrAlY coatings on SIMP steel at 300 °C. The corrosion behavior, microstructural evolution, and adhesion stability were investigated by static LBE exposure at 500 °C for up to 2000 h, combined with SEM/EDS, XRD, TEM, and progressive-load scratch testing. The results show that the AlO x -enriched surface significantly improves the protective performance of the coating in high-temperature LBE. Compared with the FeCrAlY coating, the FeCrAlY/AlO x coating forms a multilayered oxide scale composed of alternating Fe-Cr-Al-O spinel-related oxide layers and Al–O-enriched transient oxide layers. The FeCrAlY/AlO x coating also exhibited markedly improved adhesion retention, maintaining approximately 94.8% and 53.2% of its initial adhesion value (Lc 1 ) after 1000 h and 2000 h, respectively, whereas the FeCrAlY coating retained only approximately 21.2% and 18.3%. In contrast, the FeCrAlY coating develops a porous surface scale with limited barrier performance and exhibits pronounced Cr enrichment along the coating/substrate interface, which is accompanied by the 78.8% and 82.7% reductions of Lc 1 after 1000 h and 2000 h. The improved performance of the FeCrAlY/AlO x coating is attributed to the Al-enriched near-surface region, which promotes the timely formation of a protective scale and helps maintain interfacial stability during prolonged LBE exposure.