Microstructure evolution and chromium suppression mechanism in pre-oxidized Ce/Co-coated AISI 441 stainless steel for solid oxide fuel cell interconnects

Chromium volatilization and the poorly-regulated Cr₂O₃ scale pose significant challenges to the oxidation resistance and electrochemical performance of solid oxide fuel cell (SOFC) interconnects. This study develops a Co₃O₄/CeO₂/Cr₂O₃ tri-layer diffusion barrier via a pre-oxidation treatment to mitigate these issues. The results show that the pre-oxidation at 800 °C enhanced both the coating densification and adhesion strength, resulting in a peak critical load (L_c) of 17.7 ± 0.25 N. After 100 h of thermal exposure at 750 °C, the optimized pre-oxidation treatment effectively limits the thermal growth of the Cr₂O₃ scale, maintaining a thickness of 134 nm, which is an increase of only 7.2 % compared to the pre-exposure stage. Furthermore, the post-exposure chromium concentration on the coating surface remains remarkably low (2.3 at. %), with only a slight increase of 0.43 at. %. These findings elucidate the mechanism by which the tri-layer diffusion barrier enhances oxidation resistance and reduces area-specific resistance (ASR), providing a feasible pathway for the development of durable and high-performance SOFC interconnects.