目的 研究Nb含量对奥氏体耐热钢在水蒸气高温环境下氧化行为的影响。方法 选取两种不同成分的HR3C奥氏体耐热钢，在700℃、25 MPa纯水蒸气环境中进行氧化实验，实验周期为1000 h。采用扫描电子显微镜、X射线衍射仪以及光学显微镜，比较两种合金的高温氧化动力学结果，并对氧化物的微观形貌和成分以及合金的组织形貌进行观察和分析，探究Nb对HR3C奥氏体耐热钢蒸汽氧化的影响机制。结果 Nb的含量对HR3C奥氏体耐热钢的蒸汽氧化性能产生了显著的影响，HR3C-0#合金的氧化质量增量为0.7746 mg/cm²，显微硬度为258.9HV，HR3C-1#合金的氧化质量增量为1.716 19 mg/cm²，显微硬度为201.4HV，并且两种合金在蒸汽氧化过程中均出现了晶粒细化。结论 当Nb的含量在相对较低范围时，HR3C奥氏体耐热钢表现出良好的抗蒸汽氧化性能及较高的硬度;当合金中Nb的含量过高时，会恶化合金的抗蒸汽氧化性能以及显微硬度，样品表面生成了大量非保护性的岛状Fe2O3，并且伴随着组织结构发生晶粒细化的现象。

The work aims to study the effect of Nb content on the steam oxidation behavior of austenitic heat-resistant steel in high temperature environment.Two HR3C austenitic heat-resistant steels with different composition were selected and subjected to oxidation experiments in a pure water vapor environment at 700 ℃ and 25 MPa for 1000 h. Scanning electron microscopy, X-ray diffraction instrument and optical microscopy technology were used for comparative studying on high temperature oxidation kinetics, microstructure evolution and the composition constituent of the oxides and alloys, to observe and investigate the effect of Nb on the steam oxidation behavior of HR3C austenitic heat-resistant steels. The content of Nb had a significant effect on the steam oxidation performance of HR3C austenitic heat-resistant steel. The oxidation weight gain of HR3C-0# alloy was 0.7746 mg/cm2, the microhardness was 258.9HV. And the weight gain of HR3C-1# alloy was 1.716 19 mg/cm2, the microhardness was 201.4HV. Grain refinement occurred in both alloys during the steam oxidation process. When the content of Nb is in a relative lower range, the HR3C austenitic steel exhibits good resistance to steam oxidation and high hardness. On the other hand, the steam oxidation resistance and microhardness of the alloy is deteriorated as the content of Nb in the alloy is over high. A large amount of unprotected oxide-island Fe2O3 formed on the surface of the sample, accompanied by the appearance of grain refinement.