The oxidation behavior of alumina-forming alloys was studied after oxidation treatments conducted at 900 °C for 24 h in air or in steam. Alloys with sulfur contents ranging from 1 to 82 ppm in wt% were used. The influence of trace sulfur as well as the presence of steam in the oxidizing atmosphere were investigated. Under oxidation conditions, higher sulfur contents led to higher mass gains and the trend was more pronounced in steam than in air. Oxides were identified by Raman spectroscopy: a thin and continuous α-Al₂O₃ layer was formed at the metal-oxide interface in all cases. The mass gain differences were caused by other oxides formed at the surface of the samples—mainly spinel and Cr₂O₃—and in the internal oxidation zone too— mainly α-Al₂O₃ and θ-Al₂O₃—indicating that the protectiveness of the alumina layer greatly depends on the sulfur content in the base material and the oxidizing atmosphere. In order to explain this phenomenon, oxide structures were analyzed at various scales using scanning electron microscopy, transmission electron microscopy and nanoscale secondary ion mass spectrometry. Sulfur was detected at metal-oxide interfaces and also in the alumina layer in regions enriched with chromium. In addition, we demonstrate that steam oxidation leads to finer alumina grains as compared to air oxidation. Finally, the relationship between oxidation conditions, nanoscaled structural features and oxidation kinetics is discussed.

在900°C下在空气或蒸汽中进行24 h氧化处理后，研究了形成氧化铝的合金的氧化行为。使用的硫含量范围为1至82 ppm（重量百分比）的合金。研究了痕量硫的影响以及氧化气氛中蒸汽的存在。在氧化条件下，较高的硫含量导致较高的质量增加，并且蒸汽中的趋势比空气中的趋势更明显。氧化物进行鉴定通过拉曼光谱：薄且连续的α-Al ₂ ö ₃在所有情况下，金属氧化物界面上形成层。质量增益差异是由样品表面形成的其他氧化物（主要是尖晶石和Cr ₂ O _{3）引起的}-and在内部氧化区too-主要的α-Al ₂ ö ₃和θ-Al系₂ ö ₃-表示氧化铝层的保护性在很大程度上取决于基材中的硫含量和氧化气氛。为了解释这种现象，使用扫描电子显微镜，透射电子显微镜和纳米级二次离子质谱法以各种尺度分析了氧化物结构。在金属氧化物界面以及富含铬的区域的氧化铝层中都检测到了硫。此外，我们证明了与空气氧化相比，蒸汽氧化可产生更细的氧化铝颗粒。最后，讨论了氧化条件，纳米尺度结构特征和氧化动力学之间的关系。