Oxygen diffusion and crack growth for a nickel-based superalloy under fatigue-oxidation conditions
Oxygen diffusion and crack growth for a nickel-based superalloy under fatigue-oxidation conditions
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DOI：
10.1016/j.msea.2012.12.088
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发表时间：
2013-04
期刊：
影响因子：
6.4
通讯作者：
A. Karabela;Liguo Zhao;B. Lin;J. Tong;M. Hardy
中科院分区：
文献类型：
--
作者：
A. Karabela;Liguo Zhao;B. Lin;J. Tong;M. Hardy
先进的显微镜表征和数值模拟已经进行了调查氧扩散和裂纹扩展的镍基高温合金在疲劳氧化条件下。聚焦离子束（FIB）检测发现，氧渗透到材料中并伴随内部氧化，导致材料脆化和失效。在750°C及以上的温度下，施加的疲劳载荷往往会增加内部氧化的程度。使用子模型技术，在晶粒水平的氧渗透的有限元分析已进行量化的疲劳氧化损伤和校准的扩散参数的基础上测量的最大深度的内氧化。在有限元模型中明确地考虑了晶粒微观结构，其中晶界被视为氧扩散的主要路径。采用顺序耦合的力学扩散分析来考虑疲劳加载过程中变形对扩散的影响，其中材料本构行为由晶粒级的晶体塑性模型描述。氧化辅助裂纹扩展的预测也进行了在高温下从附近的疲劳裂纹尖端的氧扩散的有限元分析。在考虑裂纹尖端氧浓度和累积非弹性应变的基础上，建立了裂纹扩展的失效曲线。从疲劳-氧化失效曲线的预测相比，以及与三角形和驻留加载波形的实验结果，取得了显着的改善，从粘塑性模型单独的预测。
Advanced microscopy characterisation and numerical modelling have been carried out to investigate oxygen diffusion and crack growth in a nickel-based superalloy under fatigue-oxidation conditions. Penetration of oxygen into the material and the associated internal oxidation, which leads to material embrittlement and failure, have been found from Focused Ion Beam (FIB) examinations. Applied fatigue loading tends to enhance the extent of internal oxidation for temperatures at 750°C and above. Using a submodelling technique, finite element analyses of oxygen penetration at grain level have been carried out to quantify the fatigue-oxidation damage and calibrate the diffusion parameters based on the measurements of maximum depth of internal oxidation. The grain microstructure was considered explicitly in the finite element model, where the grain boundary was taken as the primary path for oxygen diffusion. A sequentially coupled mechanical-diffusion analysis was adopted to account for the effects of deformation on diffusion during fatigue loading, for which the material constitutive behaviour was described by a crystal plasticity model at grain level. Prediction of oxidation-assisted crack growth has also been carried out at elevated temperature from the finite element analyses of oxygen diffusion near a fatigue crack tip. A failure curve for crack growth has been constructed based on the consideration of both oxygen concentration and accumulated inelastic strain near the crack tip. The predictions from the fatigue-oxidation failure curve compared well with the experimental results for triangular and dwell loading waveforms, with significant improvement achieved over those predicted from the viscoplastic model alone.