617镍基合金蠕变-疲劳交互力学行为与微观组织演变

Creep-Fatigue Interaction Behaviors and Microstructure Evolution of Ni-based Superalloy 617

对先进超超临界汽轮机转子侯选材料617镍基合金进行725℃不同拉伸应变保持时间的蠕变-疲劳交互试验,对4个应变保持时间下的试样力学行为和微观组织进行比较分析。结果表明,在短时间应变保持下的蠕变-疲劳失效机制是疲劳裂纹和氧化空洞及氧化晶界的连接贯通引发的沿晶破坏;随着应变保持时间增加,晶界抗氧化性和晶界及晶内强度提高,合金抵抗蠕变和裂纹扩展的能力增强;失效循环次数降低,但总运行时间增加。对不同应变保持时间的裂纹形态、组织缺陷、碳化物和析出相的演变以及不同形态的γ’相的形成机制进行了讨论,揭示了617镍基合金蠕变-疲劳交互力学行为与组织演变的相互影响机理,为先进超超临界汽轮机机组高温部件选材和使用提供参考。

Creep-fatigue test strain-controlled with different tensile strain holding times at 725 ℃ were done on Nickel-based superalloy 617 as a typical candidate material for turbine rotor using an advanced ultra super critical power plant.The mechanical behavior and microstructure evolution under 4 strain holding times were compared and analyzed.The results show that creep-fatigue failure mechanism under short-time strain holding is intergranular failure caused by the connection of fatigue cracks and oxidized cavities and oxidized grain boundaries.As the strain holding time increases,the grain boundary oxidation resistance and the intergranular and intragranular strength increase,and the ability to resist creep and crack propagation increases.The number of 617creep-fatigue failure cycles decreases while the total running time increases.The crack morphology,microstructure defects,the evolution of carbides and precipitated phases and the formation mechanisms of different γ’ phases were discussed.It revealed the influence mechanism between creep-fatigue interactive mechanical behavior and microstructure evolution of 617 Nickel-based alloy,which provides reference for the selection and use of high-temperature components of A-USC turbine units.