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5479 |
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Wednesday, June 07, 2017, Hall 12 2:20 PM Power Generation - Fuel Cell |
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Atmospheric plasma-sprayed coatings for SOFCs |
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Francesco Bozza* / Turbocoating S.p.a., Italy Nelso Antolotti / Turbocoating S.p.a., Italy Luca Tagliaferri/ Turbocoating S.p.a., Italy Martin Thoma/ Forum of Technology, Germany Enea Ghidini/ Turbocoating S.p.a., Italy |
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The aim of the present work, was to deeply investigate the results achieved during the SCORED 2:0 EU funded project. Nowadays stainless steels are becoming the most employed material for interconnectors in solid oxide fuel cells (SOFC). The corrosion resistance is achieved by adding 20-25 wt-% chromium to the steel. At operating conditions, these steels form a double-layered structure at the surface, which prevents further oxidation. However, chromium is prone to evaporate at the operating temperature. Chromium poisoning is a widely recognized degradation mechanism in SOFCs. The gaseous Cr-rich compounds, formed during the working life, reach the cathode material leading to an overall loss of efficiency of the SOFC and to a premature failure of the stack. Manganese-cobalt-oxide spinel (MCO) and manganese-cobalt-oxide doped with iron (MCF) were found to be potential candidates to prevent Cr evaporation. Those spinels are applied to form a thin and dense coating on the surface of the steel interconnector, to act as a barrier against Cr diffusion, without decreasing the electrical conductivity of the interconnector. Moreover, those systems can be improved by performing surface pre-treatments. The behavior of MCO and MCF coatings applied by atmospheric plasma spray (APS) on different stainless steels (K41, Sanergy HT and Crofer 22H) with and without pre-treatment was analyzed. Exposure tests and area specific resistance measurements were performed in order to evaluate the ohmic resistance and the Cr-evaporation rate of the deposited layers. The evolution of the coating microstructure was evaluated by means of SEM and XRD analysis. After laboratory-scale tests, MCO and MCF coatings were deposited on real parts and long term tests were performed in order to evaluate the behavior of an assembled stack. |