In situ investigation of atmospheric plasma-sprayed Mn–Co–Fe–O by synchrotron X-ray nano-tomography

Nikolas Grünwald (1) , Pierre Lhuissier (2) , Luc Salvo (2) , Julie Villanova (3) , Norbert H Menzler (1) , Olivier Guillon (1) , Christophe Martin (2) , Robert Vassen (1)

1 FZJ - Forschungszentrum Jülich GmbH | Centre de recherche de Jülich | Jülich Research Centre
2 SIMaP - Science et Ingénierie des Matériaux et Procédés
3 ESRF - European Synchrotron Radiation Facility

Applying atmospherically plasma-sprayed (APS) Mn 1.0 Co 1.9 Fe 0.1 O 4 (MCF) protective coatings on interconnector steels minimized the chromium-related degradation within solid oxide fuel cell stack-tests successfully. Post-test characterization of the coatings disclosed a severe microstructural and phase evolution. A self-healing of micro-cracks, the formation and agglomeration of small pores, the occurrence of a dense spinel layer at the surface and a strong elemental de-mixing were reported in ex situ experiments. In the present publication , we prove for the first time these mechanisms by tracking the microstructure in situ at a single APS coating using synchrotron X-ray nano-tomography at the European Synchrotron Radiation Facility. Therefore, a 100-lm-long cylindrical sample with a diameter of 123 lm was cut from an APS-MCF free-standing layer and measured within a high-temperature furnace. All microstructural changes mentioned above could be verified. Porosity measurements reveal a decrease in the porosity from 9 to 3% during the annealing, which is in good accordance with the literature. Additionally, a partial detachment of an approximately 5-lm-thick layer at the sample surface is observed. The layer is dense and does not exhibit any cracks which are penetrating the layer. This kind of shell is assumed to be gastight and thus protecting the bulk from further oxidation.

Domaines: Matériaux

Nikolas Grünwald, Pierre Lhuissier, Luc Salvo, Julie Villanova, Norbert H Menzler, et al.. In situ investigation of atmospheric plasma-sprayed Mn–Co–Fe–O by synchrotron X-ray nano-tomography. Journal of Materials Science, 2020, 55 (27), pp.12725-12736. ⟨10.1007/s10853-020-04916-9⟩. ⟨hal-02952496⟩