Mechanisms of Oxide Scale Formation on Ferritic Interconnect Steel in Simulated Low and High pO2 Service Environments of Solid Oxide Fuel Cells
Mechanisms of Oxide Scale Formation on Ferritic Interconnect Steel in Simulated Low and High pO2 Service Environments of Solid Oxide Fuel Cells
复制标题
固体氧化物燃料电池模拟低和高 pO2 使用环境中铁素体互连钢氧化皮形成机制
作者：
L. Niewolak;D. Young;H. Hattendorf;L. Singheiser;W. Quadakkers
Laves 相强化铁素体钢 Crofer 22 H 最近被提议作为固体氧化物燃料电池 (SOFC) 互连件的结构材料。在本研究中，将 Crofer 22 H 在 800 °C 下的氧化动力学与无锰批次暴露在空气和 Ar-H2-H2O 中的氧化动力学进行了比较，后者模拟了 SOFC 的阳极气体。主要重点研究等温反应早期阶段以及长期不连续暴露期间 Crofer 22 H 的氧化机制。定义了空气和模拟阳极气体 (SAG) 中氧化机制的差异。研究发现 Crofer 22 H 在空气中的氧化速率最初比 SAG 中的氧化速率慢，但在较长的暴露时间后观察到相反的效果。气氛成分对氧化速率的影响取决于内部氧化铬层被外部 Cr/Mn 尖晶石层覆盖的时间依赖性程度。在两种测试气体中，Crofer 22 H 中添加少量硅会导致在氧化的早期阶段形成内部二氧化硅；这种效应在较长的曝光时间后消失。对于两种测试气氛，氧化皮中钛的掺入量有所不同，因为氧分压影响钛在氧化铬中的溶解度，尤其是尖晶石相中的溶解度。
The Laves phase strengthened ferritic steel Crofer 22 H has recently been proposed as construction material for interconnects in solid oxide fuel cells (SOFCs). In the present study, the oxidation kinetics of Crofer 22 H at 800 °C was compared with that of a Mn-free batch during exposure in air and Ar–H2–H2O, the latter simulating the anode gas of a SOFC. Main emphasis was put on studying the oxidation mechanisms of Crofer 22 H during the early stages of isothermal reaction as well as during long-term discontinuous exposure. Differences in oxidation mechanisms in air and simulated anode gas (SAG) were defined. Oxidation rates for Crofer 22 H in air were found to be initially slower than in SAG, but the opposite effect was observed after longer exposure times. This effect of atmosphere composition on the oxidation rate is shown to be governed by the time dependent extent to which the inner chromia scale layer is covered by an outer Cr/Mn spinel layer. In both test gases the minor addition of silicon to Crofer 22 H resulted in internal silica formation during the very early stages of oxidation; this effect vanished after longer exposure times. Incorporation of titanium in the scale differed for the two test atmospheres because the oxygen partial pressure affects titanium solubility in chromia and especially the spinel phase.