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首页> 外文期刊>International Journal of Fatigue >High temperature fatigue and creep-fatigue behaviors in a Ni-based superalloy: Damage mechanisms and life assessment
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High temperature fatigue and creep-fatigue behaviors in a Ni-based superalloy: Damage mechanisms and life assessment

机译：镍基高温合金的高温疲劳和蠕变疲劳行为：损伤机理和寿命评估

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摘要

The low cycle fatigue (LCF) and creep-fatigue behaviors of Ni-based GH4169 superalloy are investigated by uniaxial strain-controlled fully-reversed testing at 650 degrees C. Compared with LCF tests, the effects of tensile and compressive strain hold times on creep-fatigue lifetimes are experimentally explored with varying total strain ranges in the present work. In order to elucidate the damage mechanisms under complex loading waveforms, an additional series of tests with both tensile and compressive hold times are carried out at a given total strain range of 2.0%. Posterior to the cyclic tests, main-crack-failure modes and secondary cracking modes are studied via optical microscopy (OM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) techniques. Main-crack failure mechanisms are examined by the fracture appearance observations. Cracking modes are explored through quantitative characterization on the distributions of secondary cracks in the longitudinal cross sections under different loading waveforms. Moreover, a generalized life model based on linear damage summation (LDS) framework and energy dissipation criterion (EDC) is elaborated to estimate the damage mechanisms of fatigue, creep and oxidation. The prediction results can well establish the correlations between the reductions of numbers of cycles to failure and the presences of different damage mechanisms under respective loading waveforms.
机译：通过在650摄氏度下的单轴应变控制全反向试验研究了镍基GH4169合金的低周疲劳（LCF）和蠕变疲劳行为。与LCF测试相比，拉伸和压缩应变保持时间对蠕变的影响在当前工作中，通过改变总应变范围来实验性地探索疲劳寿命。为了阐明复杂载荷波形下的损伤机理，在给定的总应变范围为2.0％的情况下，进行了一系列拉伸和压缩保持时间的附加测试。在循环测试之后，通过光学显微镜（OM），扫描电子显微镜（SEM）和电子背散射衍射（EBSD）技术研究了主裂纹-断裂模式和次级裂纹模式。通过裂缝外观观察来检查主裂缝失效机理。通过定量表征在不同载荷波形下纵截面中二次裂纹的分布，探索了裂纹模式。此外，详细阐述了基于线性损伤总和（LDS）框架和能量耗散准则（EDC）的广义寿命模型，以估计疲劳，蠕变和氧化的损伤机理。预测结果可以很好地建立失效周期数的减少与相应载荷波形下不同损伤机制的存在之间的相关性。

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