Conductivity and Oxidation Behavior of Fe-16Cr Alloy as Solid Oxide Fuel Cell Interconnect Under Long-Stability and Thermal Cycles

doi:10.1007/s40195-020-01147-4

Abstract

Abstract:

Conductivity and oxidation behavior of Fe-16Cr alloy were investigated under long-term stability operation at 750 °C and thermal cycles from room temperature to 750 °C. The results showed that the area specific resistance (ASR) of Fe-16Cr alloy increased over time and reached about 56.29 mΩ cm² after 40,000 h of long-term stability operation at 750 °C by theoretical calculation. The ASR of Fe-16Cr remained about 11 mΩ cm² after 52 thermal cycles from room temperature to 750 °C. The analysis of structure showed that the oxidized phase on the surface of Fe-16Cr was mainly composed of Cr₂O₃ and FeCr₂O₄ spinel phase under long-term stability operation at 750 °C. While the Cr₂O₃ phase was mainly observed on the surface of Fe-16Cr alloy after 52 thermal cycles, the oxidation rates of Fe-16Cr alloy were 0.0142 μm h^-1 and 0.06 μm cycle^-1 under long-term stability operation and under thermal cycle, respectively. The property of Fe-16Cr alloy with 2.6 mm thickness met the lifespan requirement of interconnect for solid oxide fuel cell (SOFC) stacks. The Cr element all diffused onto oxidation surface, indicating that it was necessary to spray a coating on the surface to avoid poisoning cell cathode of SOFCs. Two 2-cell stacks were assembled and tested to verify the properties of Fe-16Cr alloy as SOFC interconnect under long-term stability operation and thermal cycle condition.

Key words: Fe-16Cr, Interconnect, Long-term stability, Thermal cycle, Solid oxide fuel cell

Jianwu Zhou, Qiangfeng Chen, Junkang Sang, Rongmin Wu, Zhuobin Li, Wanbing Guan. Conductivity and Oxidation Behavior of Fe-16Cr Alloy as Solid Oxide Fuel Cell Interconnect Under Long-Stability and Thermal Cycles[J]. Acta Metallurgica Sinica (English Letters), 2021, 34(5): 668-674.

Figures/Tables 13

Table 1 Composition of Fe-16Cr alloy sample

Fe	Cr	Ni	C	Mn	Si	P	S
Bal.	16.14	0.044	-	0.209	0.279	0.028	-

Fig. 1 Schematic diagram of DC four-probe method: a Pt wire on Ag mesh; b Pt wire on alloy

Fig. 2 Schematic diagram of two-cell stack assemble

Fig. 3 ASR of Fe-16Cr alloy sample under long-term stability operation at 750 °C

Fig. 4 Microstructure of Fe-16Cr alloy sample under long-term stability operation at 750 °C

Fig. 5 XRD result of Fe-16Cr alloy sample after long-term stability operation at 750 °C

Fig. 6 Element distribution of Fe-16Cr alloy sample after long-term stability operation at 750 °C

Fig. 7 ASR of Fe-16Cr alloy sample under thermal cycling from room temperature to 750 °C

Fig. 8 Microstructure of Fe-16Cr alloy sample after thermal cycles

Fig. 9 XRD pattern of Fe-16Cr alloy sample after thermal cycles

Fig. 10 Element distribution of Fe-16Cr alloy sample after thermal cycles

Fig. 11 Stability curves of two-cell stack a, voltage drop of interconnect inside two-cell stack b

Fig. 12 Cycling curves of two-cell stack a, voltage drop of interconnect inside stack b

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