为探究高Nb锆合金在含氧蒸汽中耐腐蚀性能恶化的机理，研究了Zr-0.75Sn-0.35Fe-0.15Cr-1.0Nb (质量分数，%)合金在除氧(DE)、300 μg/kg溶解氧(DO)、1000 μg/kg DO的400℃、10.3 MPa过热蒸汽中的腐蚀行为，采用SEM、TEM和XPS分析了氧化膜的显微组织和Nb元素价态。结果表明：Zr-0.75Sn-0.35Fe-0.15Cr-1.0Nb合金在400℃过热蒸汽中的耐腐蚀性能随着DO浓度升高而变差；合金在含氧蒸汽中耐腐蚀性能恶化的机理主要有2方面，一方面是DO加速了氧化膜中Nb元素的氧化，促进了Nb²⁺向Nb⁵⁺的转换；另一方面是DO促进了第二相氧化成m-Nb₂O₅以及非晶，进而促进了裂纹的萌生与生长，裂纹为O的扩散提供了快速通道，氧化膜显微组织的演化速率更快，最终加速了合金的腐蚀进程。

In some water-cooled nuclear power reactors, a hydrogenation-deoxygenation device is generally not used to simplify the system and save space, which can increase dissolved oxygen (DO) concentration in primary loop water. The increase in DO concentration will inevitably affect the corrosion resistance of zirconium alloy cladding materials. In particular, DO will accelerate the corrosion of Nb-containing zirconium alloys, and the corrosion rate of zirconium alloys with high Nb content is sensitive to DO concentration. In exploring the deterioration mechanism of the corrosion resistance of high-Nb-containing zirconium alloys in oxygen-containing steam, the corrosion behavior of the Zr-0.75Sn-0.35Fe-0.15Cr-1.0Nb (mass fraction, %) alloy was studied in superheated steam through deoxygenation, with 300 μg/kg of DO and 1000 μg/kg of DO at 400^oC and 10.3 MPa. The corrosion behavior was characterized by measuring the mass gain per unit area. SEM was used to observe the fracture morphology of the oxide film; TEM-EDS was used to observe and analyze the morphology, elemental distribution, and crystal structure of the alloy, second-phase particles (SPPs), and oxide film. The elemental distribution on the outer surface of the oxide film was analyzed by XPS, and the valence state of Nb was determined in accordance with the binding energy to analyze the influence of DO on the oxidation behavior of Nb in the oxide film. Results show that the corrosion resistance of the Zr-0.75Sn-0.35Fe-0.15Cr-1.0Nb alloy in superheated steam at 400^oC deteriorates with the increase of DO concentration. The deterioration mechanism of the corrosion resistance of the alloy in oxygen-containing steam is proposed. On the one hand, DO accelerates the oxidation of Nb in the oxide film and promotes the conversion of Nb²⁺ to Nb⁵⁺. On the other hand, DO promotes the oxidation of SPPs to m-Nb₂O₅ (monoclinic) and amorphous phase, thereby promoting the initiation and growth of cracks. These newly generated cracks provide more channels for the diffusion of O^2- and other oxidizing ions to accelerate the oxidation of SPPs near the cracks and the microstructural evolution of the oxide film, thereby accelerating the corrosion of the alloy.