In the present study, the ferritic steel Crofer 22 H as potentially suitable interconnect material for SOEC stacks as well as joints between the steel and Ni- and CuNi contact materials was investigated with respect to the behaviour in simulated service environments of an SOEC system for CO2/H2O co-electrolysis. Exposures up to 1000 h at temperatures between 600 and 800 °C were carried out in CO2/H2O- and CO/H2-rich gases, thus simulating conditions at the stack inlet and outlet, respectively. It was found that the steel formed protective surface oxide scales consisting of chromia and/or Cr/Mn spinel in all studied test conditions. No indication of carbon transfer from the gas atmosphere into the steel was found even in the high carbon activity CO/H2-rich gas simulating stack outlet conditions. However, in the latter gas substantial carbon transfer from the gas to the steel via the Ni- or CuNi-wires resulted in the formation of a carburized zone with substantial M23C6 and/or M7C3 precipitate formation. This effect was more pronounced for the joints of the steel with the Ni-wire than with the CuNi-wire. In the gas simulating the service environment at the stack inlet, only minor carbon transfer was found in case of the Ni/steel joint at 600 °C but not at 800 °C. In case of the CuNi-wires, partial loss of contact between wire and interconnect steel and formation of Kirkendall voids as a consequence of interdiffusion between wire and steel were observed. The experimental results are discussed using thermodynamic considerations involving gas equilibria and stability of possible external and/or internal formation of oxide and carbide phases.

中文翻译：

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金属材料在用于 Power-to-X 应用的 CO2/H2O 共电解系统的模拟服务环境中的行为

在本研究中，研究了铁素体钢 Crofer 22 H 作为 SOEC 堆以及钢与 Ni 和 CuNi 接触材料之间的接头的潜在合适互连材料，研究了 SOEC 系统在 CO2 模拟服务环境中的行为/H2O 共电解。在富含 CO2/H2O 和 CO/H2 的气体中，在 600 至 800 °C 的温度下进行长达 1000 小时的暴露，从而分别模拟烟囱入口和出口的条件。发现在所有研究的测试条件下，钢形成了由氧化铬和/或铬/锰尖晶石组成的保护性表面氧化皮。即使在模拟烟囱出口条件的高碳活性 CO/H2 气体中，也没有发现碳从气体气氛转移到钢中的迹象。然而，在后一种气体中，大量的碳通过 Ni 或 CuNi 线从气体转移到钢，导致形成渗碳区，并形成大量 M23C6 和/或 M7C3 沉淀物。这种效果对于钢与 Ni 线的接头比与 CuNi 线的接头更明显。在模拟烟囱入口使用环境的气体中，在 600 °C 下的 Ni/钢接头的情况下，仅发现少量碳转移，而在 800 °C 下则没有。在 CuNi 线的情况下，观察到线和互连钢之间的部分接触丧失以及由于线和钢之间的相互扩散而形成柯肯德尔空洞。使用涉及气体平衡和氧化物和碳化物相的可能的外部和/或内部形成的稳定性的热力学考虑来讨论实验结果。