不同氧化条件下 Cr35 Ni45 Nb合金组织特征及其与持久寿命的关系

以Cr35Ni45Nb合金为研究对象，进行不同气氛条件下高温时效及高温持久试验，并结合扫描电镜及定量电子探针对样品表面及横截面的观察分析，系统研究不同氧化条件下Cr35Ni45Nb合金组织演变与持久寿命的关系。结果表明：随着处理时间的延长，管材边缘及内部组织均逐渐发生变化。氧化序列体现为先是在样品边界不同地点形成不连续的氧化膜，随后氧化膜连成一体形成连续氧化膜，同时贫化区也逐渐形成；由于温度波动，氧化膜破裂脱落，而在氧分压较高的时效环境中，氧化膜得不到及时修复，使得贫化区晶界中出现内氧化。此外，在空气中氧化与在真空充氩气石英管中持久试验结果表明，较薄的连续氧化膜有助于提高合金的蠕变性能，而随着高温时效时间的延长，边界贫化区逐渐形成，氧化膜破裂及内氧化的发生，使得合金的蠕变性能逐渐弱化。

Relationship between high temperature microstructural evolution and creep rupture life of Cr35 Ni45 Nb alloy under different oxidation conditions

The relationship of creep rupture life and microstructural evolution under different high temperature oxidation conditions for Cr35Ni45Nb alloy was studied by using SEM and quantitative electronic probe analysis. It was found that the microstructure gradu-ally varied both in the edge and inside of the tube with increasing treatment time. The oxidation sequence showed that discontinuous oxidation films firstly developed at different places from the surface of the tube specimen, then they became continuous, and the carbide depleted zone developed as well during the high temperature oxidation process. As time went by, the oxidation films ruptured with temperature fluctuation, the characteristic of a higher oxygen partial pressure during the aging process resulted in the untimely recovery of the broken oxide films, and internal oxidation occurred at grain boundaries. Furthermore, creep rupture tests under differ-ent pretreating conditions of oxidation in air and argon gas atmosphere showed that the newly-built thin and continuous oxidation films improved the creep properties, while with increasing aging time, carbide depleted zone formation, oxidation film rupture and internal oxidation could decrease the creep properties of this alloy.