Investigation of coated FeCr steels for application as solid oxide fuel cell interconnects under dual-atmosphere conditions

11–23% Cr steels for solid oxide fuel cell interconnect applications at 800 °C – How the coating determines oxidation kinetics

“…After 500 h, 444 had the least mass gain, followed by Crofer 22 APU, 430, 409, and 441. These findings agree well with earlier published data on 444, showing that 444 has a slower rate of oxide scale growth than 441 at 750 C and 850 C [46]. The mass gains measured after chromium evaporation (isothermal exposure) for 500 h are similar to the mass gains measured during the discontinuous exposure except for 409.…”

“…The corrected mass gain of 444 was still lower than that for 430 and 441 despite that it had higher chromium evaporation and no reactive elements. The results are in agreement with earlier studies on uncoated 441 and 444 [46,50,56,57]. The beneficial effect of reactive elements has been known for decades although the exact mechanism is still debated.…”

“…Higher laves phase precipitation might affect the diffusion of Mn to the oxide scale. Ali-L€ oytty et al [48] have shown that (FeCrSi) 2 (MoNb) laves phases formed at grain boundaries strongly limit the diffusion of Mn to the oxide scale at 650 C. The initially higher rate of chromium evaporation of Mo-containing steels has been reported earlier, which supports this hypothesis: the initial rate of chromium evaporation of 444 is higher than 441 [46], and Sanergy HT is higher than Crofer 22H [49] at 750 C. No difference in chromium evaporation between 441 and 444, having similar Mn concentrations, was found at 850 C [46,50]. This finding is attributed to the faster formation of a (Cr,Mn) 3 O 4 spinel at higher temperatures possibly in combination with a larger share of bulk Mn diffusion to the surface, which would minimize the effect of the laves phases on Mn diffusion.…”

Impact of CeCo-Coated Metallic Interconnectors on SOCs Towards Performance, Cr-Oxide-Scale, and Cr-Evaporation

“…1,2,[7][8][9] These can be made of chromia based alloys or ferritic stainless steels with the ability to form a chromium (Cr) oxide layer. [10][11][12][13] Ferritic stainless steels take advantage in machinability, costs, mechanical properties and have a moderately conductive oxide scale. 11,14,15 The steel grade Crofer 22 APU, tailormade for MIC, is extensively studied and used in commercialized stacks for fuel cell as well as electrolysis mode.…”

“…[10][11][12][13] Ferritic stainless steels take advantage in machinability, costs, mechanical properties and have a moderately conductive oxide scale. 11,14,15 The steel grade Crofer 22 APU, tailormade for MIC, is extensively studied and used in commercialized stacks for fuel cell as well as electrolysis mode. [15][16][17] Numerous further steel grades such as AISI 441, 444, 430, 409 and others were investigated in literature.…”