Long-term (4 year) degradation behavior of coated stainless steel 441 used for solid oxide fuel cell interconnect applications

The present work aims to investigate the long-term stability of Ce/Co coated AISI 441 used as an interconnect material in solid oxide fuel cells (SOFC). Being a commercially available alloy the use of AISI 441 would greatly reduce the cost of SOFCs in comparison to tailor-made interconnect materials such as Crofer 22 APU. To analyze the long-term stability Ce/Co coated AISI 441 is exposed in air at 800 \ub0C for up to 38 000 h. Mass gain values are recorded continuously. After 7 000, 23 000, and 35 000 h area specific resistance (ASR) measurements are performed, and cross-sections are prepared and analyzed using scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) spectroscopy. Cr-evaporation measurements are conducted on samples exposed for up to 38 000 h

Development of robust metal-supported SOFCs and stack components in EU METSAPP consortium

The potential of MS-SOFCs was demonstrated through the previous EU METSOFC project, which concluded that the development of oxidation resistant novel metal-supported solid oxide fule cell (MS-SOFC) design and stack is the requirement to advance this technology to the next level. The following EU METSAPP project has been executed with an overall aim of developing advanced metal-supported cells and stacks based on a robust, reliable and up-scalable technology. During the project, oxidation resistant nanostructured anodes based on modified SrTiO3 were developed and integrated into MS-SOFCs to enhance their robustness. In addition, the manufacturing of metal-supported cells with different geometries, scalability of the manufacturing process was demonstrated and more than 200 cells with an area of ∼150 cm2 were produced. The electrochemical performance of different cell generations was evaluated and best performance and stability combination was observed with doped SrTiO3 based anode designs. Furthermore, numerical models to understand the corrosion behavior of the MS-SOFCs were developed and validated. Finally, the cost effective concept of coated metal interconnects was developed, which resulted in 90% reduction in Cr evaporation, three times lower Cr2O3 scale thickness and increased lifetime. The possibility of assembling these cells into two radically different stack designs was demonstrated

Long term (4 years) performance of Co/Ce coated 441 for SOFC interconnect applications

Co/Ce coated 441 samples were exposed at 800\ub0C in laboratory air for up to 37 000 h and subsequently characterized using different techniques. Mass gain data of all samples were recorded throughout exposure. Cr-evaporation measurements were conducted and compared with unexposed Co/Ce coated AISI 441 as well as unexposed and uncoated AISI 441. Furthermore SEM analysis on BIB cross-sections was performed on 7 000 h, 23 000 h and 35 000 h exposed Co/Ce coated 441

Cyclic oxidation of two FeCrAlRE foils at 1100 oC - The influence of the concentration of minor alloying elements on scale microstructure

Two FeCrAlRE alloys, a commercial, 0C404, and a model alloy in the form of thin foils,with different Mn, Nb, Mo and Ti concentrations were subjected to cyclic oxidation in lab air at1100\ub0C. The oxidized samples were studied by gravimetry, Grazing-Incidence X-ray Diffraction(GI-XRD), Scanning Transmission Electron Microscopy (STEM), and Energy Dispersive X-ray(EDX) analysis. The two FeCrAl alloys exhibit different oxidation kinetics; however, both alloyshave the same weight gain after 500 hours exposure. During the early stages the scale consistsmainly of α-Al2O3 together with some oxide particles containing Mn, Al, Fe and Cr formed on thealloys. After 500 hours the 0C404 scale locally also consists of larger polycrystalline regions ofMn-Cr-Al spinel. In addition, Si-rich oxide, chromia and Al-Cr oxide could be observed at themetal/oxide interface

Cyclic oxidation of two FeCrAlRE foils at 1100 oC - The influence of the concentration of minor alloying elements on scale microstructure

Two FeCrAlRE alloys, a commercial, 0C404, and a model alloy in the form of thin foils,with different Mn, Nb, Mo and Ti concentrations were subjected to cyclic oxidation in lab air at1100\ub0C. The oxidized samples were studied by gravimetry, Grazing-Incidence X-ray Diffraction(GI-XRD), Scanning Transmission Electron Microscopy (STEM), and Energy Dispersive X-ray(EDX) analysis. The two FeCrAl alloys exhibit different oxidation kinetics; however, both alloyshave the same weight gain after 500 hours exposure. During the early stages the scale consistsmainly of α-Al2O3 together with some oxide particles containing Mn, Al, Fe and Cr formed on thealloys. After 500 hours the 0C404 scale locally also consists of larger polycrystalline regions ofMn-Cr-Al spinel. In addition, Si-rich oxide, chromia and Al-Cr oxide could be observed at themetal/oxide interface

Nano coated interconnects for SOFC (NaCoSOFC)

The NaCoSOFC project is focused on the development of nano coatings for SOFC interconnects. The project is sponsored by the Nordic Top Level Research Initiative and has four project partners: Sandvik Materials Technology which is producing coated interconnects, Chalmers University of Technology and the University of Oslo that characterize samples with respect to e.g. corrosion, Cr evaporation and ASR as well as Topsoe Fuel Cell that is testing the developed interconnects in its stacks. The developed coatings are based on a combination of Co with RE elements and exhibit high corrosion resistance, 10 fold decrease in Cr evaporation and ASR values that are approximately 50% of the uncoated material