Microstructure and fretting wear performance of FeCrAl coatings after lead-bismuth corrosion

Abstract

The corrosion and fretting wear of fuel cladding are critical failure modes in lead-cooled fast reactor (LFR), which poses severe threat to both the structural integrity and operational safety of the reactor system. In this study, FeCrAl coatings with varying Al contents (8, 11, and 14 wt%) were deposited on F/M steel using magnetron sputtering. After exposure to liquid lead-bismuth eutectic (LBE) at 550 °C for 1000 h, the fretting wear performance of the coatings was systematically evaluated. The results demonstrate that the corrosion and fretting wear resistance of F/M steel are significantly enhanced by FeCrAl coatings. And the optimal wear resistance is exhibited by the FeCrAl coating with 9 wt% Cr and 8 wt% Al (sample 9-8), which has the lowest wear depth of 1.51 μm, wear volume of 0.09 × 10⁵ μm³, and wear rate of 0.23 × 10² μm³/N·m, respectively. After LBE corrosion, the coating of sample 9-8 is oxidized into a double-layered oxide structure of Fe(Cr, Al)₂O₄, consisting of columnar crystals and equiaxed nanocrystals. Simultaneously, the precipitation of Al₂O₃ and Cr₂O₃ is observed. During the fretting wear process, the hard Al₂O₃ and Cr₂O₃ particles in the third-body layer not only provided protection but also acted as solid lubricants, significantly reducing fretting-induced damage. The primary wear mechanisms of F/M steel are abrasive wear and oxidative wear, whereas those of FeCrAl coatings are abrasive wear, adhesive wear, and oxidative wear.