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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.
Taking Cr35Ni45Nb alloy as the research object, the high-temperature aging and high-temperature long-term test were carried out under different atmosphere conditions. The microstructure evolution and persistence of Cr35Ni45Nb alloy under different oxidation conditions were systematically studied by observing and analyzing the surface and cross section of the sample with SEM and quantitative electron probe. The results showed that the edge and internal structure of the pipe gradually changed with the prolongation of the treatment time.The oxidation sequence was as follows: first, the discontinuous oxide film was formed at different locations along the sample boundary, and then the oxide films were integrated into continuous oxidation Film, meanwhile the depletion zone also gradually formed. Due to the temperature fluctuation, the oxide film ruptures and falls off. However, the oxide film can not be repaired timely in the aging environment with high partial pressure of oxygen, resulting in the internal oxidation in the grain boundary of the depletion zone. In addition, long-term oxidation experiments in air and in argon-filled vacuum quartz tubes showed that the thinner continuous oxide film could improve the creep properties of the alloys. With the increase of aging temperature, the boundary depletion zone gradually increased Formation, the oxide film rupture and the occurrence of internal oxidation, making the alloy creep gradually weakened.