Enhanced spinel layer stability in Cu-alloyed FeNi coatings fabricated by spark plasma sintering: Effects of heat treatment and high-temperature oxidation on suppressing void formation

Developing a dense and continuous spinel layer is essential for solid oxide fuel cell (SOFC) interconnects to suppress Cr 2 O 3 volatilization and prevent cathode poisoning. This study investigates the influence of Cu alloying and post-heat treatment on the oxidation behavior of FeNi coatings synthesized via Spark Plasma Sintering (SPS) on Sandvik Sanergy HT steel. Post-treatment was conducted at 800 °C in vacuum, followed by a 100-h oxidation test in air. The results showed that Cu alloying significantly accelerated the formation of a protective NiFe 2 O 4 spinel layer and effectively suppresses Kirkendall void formation at the coating-oxide interface. While heat treatment further reduced void density and promoted scale growth, the synergistic effect of Cu alloying provided superior interfacial stability and structural integrity. The findings suggest that Cu-doped FeNi coatings offer a robust strategy for enhancing the long-term reliability of SOFC interconnects by facilitating continuous oxide scale development and mitigating interfacial degradation.