Long-term oxidation and chromium evaporation behavior of Al2O3-forming austenitic stainless steel for 900 °C balance-of-plant components applications in solid oxide fuel cells

The long-term operation of balance-of-plant (BoP) components in solid oxide fuel cells (SOFCs) relies on the presence of a stable and durable oxide layer. In this study, we investigate the oxidation and chromium (Cr) evaporation behaviors of two developmental alumina-forming austenitic (AFA) alloys compared to chromia-forming alloy 625 at 900 °C in air with 10% water vapor. Transpiration tests, weight gain tests, X-ray diffraction, scanning electron microscopy with energy dispersive X-ray analysis, and scanning transmission electron microscopy with energy dispersive X-ray analysis are employed to evaluate the oxidation and Cr evaporation behaviors. Our findings reveal that alloy 625 exhibits significantly higher rates of Cr evaporation compared to OC11 (Y and Hf additions) and OC11LZ (Y and Zr additions), with evaporation amounts ∼56 and ∼28 times greater, respectively. The observed differences between OC11 and OC11LZ can be attributed to variations in the formed oxide scales during long-term operation. Furthermore, we examine the influence of Hf and Zr reactive elements on the long-term oxidation and chromium evaporation behaviors, providing insights into the role of these elements in enhancing the performance and stability of the alloys.