%0 Journal Article
%A Garcia-Fresnillo, L.
%A Patel, R.
%A Niewolak, Leszek
%A Quadakkers, W. J.
%A Hua, M.
%A Wang, Q.
%A Meier, G. H.
%T Oxidation Behaviour and Phase Transformations of an Interconnect Material in Simulated Anode Environment of Intermediate Temperature Solid Oxide Fuel Cells
%J Materials at high temperatures
%V 34
%N 1
%@ 1878-6413
%C Amsterdam [u.a.]
%I Elsevier Science
%M FZJ-2016-07238
%P 61 - 77
%D 2016
%X The oxidation behaviour and the phase transformations associated with high temperature exposure of a commercial ferritic interconnect steel, Crofer 22 H, was studied in a simulated solid oxide fuel cell (SOFC) anode atmosphere at 700 °C. Special emphasis was placed on the formation of the intermetallic sigma phase. No sigma phase was detected in the bulk alloy after 500 h of exposure of bare specimens. However, specimens which were pre-coated with a layer of nickel showed formation of an interdiffusion zone after as little as 2 h of exposure and sigma phase formation occurred after 10 h. The presence of the nickel layer, which simulates the contact between ferritic steel interconnects and a nickel mesh in a SOFC results in the formation of an austenitic zone and accelerated formation of a σ-phase rich layer at the ferrite/austenite interface. The ferritic steel is transformed into austenite due to the inward diffusion of nickel, σ-phase started to nucleate at the transformed austenite grain boundaries. The nucleation is enhanced by an increased Cr/Fe-ratio at that interface due to more pronounced diffusion of Fe, compared to Cr, in the direction of the Ni-layer. Different possible mechanisms for the nucleation and growth of σ-phase were identified. The experimental results led to the conclusion that sigma nucleates in the austenite and grows following an isothermal eutectoid-like decomposition.
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000389473300008
%R 10.1080/09603409.2016.1244373
%U https://juser.fz-juelich.de/record/824680