Two high-temperature FeCrAl and FeNiCrAl alloys were exposed in a strongly nitriding environment at 900 °C and the morphology of nitridation was studied. Quasi-in-situ experiments revealed that nitridation started at specific surface sites directly related to the alloy microstructure where the alumina scale was permeable to nitrogen. FeCrAl alloy grains with (112) orientation formed outward-growing alumina scales and were susceptible to nitridation. Outward-growing scales and substrate nitridation was also observed at chromium carbide precipitates in the FeNiCrAl alloy. Both alloys suffered nitridation at reactive element-rich (Y and Zr) inclusions larger than a certain critical size. The latter type of attack is caused by cracks and pores in the scale. The findings open new avenues of research for developing the next generation of high temperature alloys with superior properties.

中文翻译：

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探索氮化环境中 FeCrAl 和 FeNiCrAl 合金上氧化铝氧化皮的失效模式

将两种高温 FeCrAl 和 FeNiCrAl 合金暴露在 900 °C 的强氮化环境中，并研究了氮化的形貌。准原位实验表明，氮化开始于与合金微观结构直接相关的特定表面位点，其中氧化铝鳞片可渗透氮。具有（112）取向的FeCrAl合金晶粒形成向外生长的氧化铝鳞片，并且易于氮化。在 FeNiCrAl 合金中的碳化铬沉淀物中也观察到向外生长的氧化皮和基体氮化。两种合金都在大于某个临界尺寸的富含活性元素（Y 和 Zr）的夹杂物处发生氮化。后一种侵蚀是由水垢中的裂纹和气孔引起的。