A Time Resolved Study of Precoated AISI 441 for SOFC Interconnects Using STEM-EELS - Part I

Precoated AISI441 for SOFC interconnectors were investigated by STEM-EELS looking at the diffusion processes in the initial stage of the oxidation. The PVD coating contained Ce and Co/Mn-alloy in two layers with at total thickness of 800nm. The samples were exposed up to 1000 hours at 800°C then characterized by TEM. Multiple linear least squares (MLLS) fitting of reference spectra aids the interpretation of the elemental maps due to overlapping edges (Figure 1). Within 4 min heat treatment the oxidation front has reached the substrate steel and Cr₂O₃ is forming at the stainless steel interface. CeO₂ acts as the barrier line for Cr and is situated between the Cr-containing spinels and the (Co,Mn)-spinel after 72 h heat treatment.