TEM Characterization of Long Term Aged Interconnect Oxide Layers from Real Stack

Steel interconnect robustness under SOFC conditions for extended operation remains a challenge. The observation and analysis of the microstructure aged in real long periods provides data to help understand degradation potentially design accelerated testing.In this study, TEM observations cross section interconnects (9000h 20000h stacks) are presented. Crofer22APU with air side coated manganese cobalt oxide (MCO) prevent chromium evaporation increase oxidation resistance. FIB-prepared lamella from inlet outlet analysed by imaging EDX. A major difference between is position Mn-rich grains chromia scale: at inlet, located metal/chromia interface (figure 1(a)) while outlet, crystals close but not directly adjacent metallic bulk 1(b)). has been observed literature an study MCO steel [1]. However, case which was both 9000h stack samples yet reported literature, best our knowledge. as well on 15000h sample SEM, may be explained differences conditions: higher temperature lower oxygen content. In addition particular Mn position, Fe particles also scale, confirming results previously described literature[2]. coating shows inner denser layer, expected after ageing high temperature[3]. Analysis segregation grain boundaries presented.More investigations necessary explain complete mechanisms MCO-coated Crofer interconnect. important role shown. understanding all reactions conditions, different locations, should designing more reliable combinations, better predictive models possibly tests.[1] S. Molin et al., « Microstructural electrical characterization Mn-Co spinel protective coatings solid cell », J. Eur. Ceram. Soc., vol. 37, no 15, p. 4781-4791, dec. 2017, doi: 10.1016/j.jeurceramsoc.2017.07.011.[2] L. V. Gambino, N. Magdefrau, M. Aindow, effects reduction step reactive consolidation cobaltite 22 APU Mater. High Temp., 32, 1-2, 142-147, janv. 2015, 10.1179/0960340914Z.00000000090.[3] B. Talic, Venkatachalam, P. Hendriksen, R. Kiebach, Comparison MnCo2O4 H, 441, 430 intermediate-temperature fuel stacks Alloys Compd., 821, 153229, avr. 2020, 10.1016/j.jallcom.2019.153229.Figure 1