| 摘要: |
| 定向凝固/单晶镍基合金在服役过程中受高温、外载和时间的复杂影响会发生微结构退化，从而导致其低周疲劳性能降低。为了预测微结构退化镍基合金的低周疲劳寿命，探索材料微结构退化导致疲劳寿命缩短的机理，假定材料在标准热处理状态下承受更大载荷而不改变材料在给定载荷下的疲劳损伤机制和规律，基于连续损伤力学和应变能密度理论建立了考虑微结构状态的镍基合金寿命预测方法。采用前期开展的微结构粗化/筏化DZ125镍基合金低周疲劳试验结果，对两种模型预测结果进行了验证。结果表明：两种模型预测结果与试验结果相吻合，模型预测结果控制在±3倍分散带内。考虑微结构状态的疲劳寿命预测方法能够有效地捕捉微结构粗化/筏化对合金低周疲劳寿命的劣化作用。该方法将高温部件的疲劳性能评估在传统的载荷-寿命二维平面上增加了考虑时间作用的微结构退化维度。 |
| 关键词: 高温合金 微结构退化 低周疲劳 损伤力学 应变能密度 寿命预测 |
| DOI：10.13675/j.cnki.tjjs.210531 |
| 分类号:V231.95 |
| 基金项目:国家科技重大专项（2017-IV-0012-0049；2019-IV-0017-0085）；国家自然科学基金（12172021）。 |
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| Low Fatigue Life Prediction Methods for Ni-based Superalloys Considering Microstructure State in Service |
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TAN Long1, YANG Xiao-guang1,2, SUN Yan-tao3, FAN Yong-sheng1,4, SHI Duo-qi1,5
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1.School of Energy and Power Engineering,Beihang University,Beijing 102206,China;2.School of Aircraft Engineering,Nanchang Hangkong University,Nanchang 330063,China;3.Beijing Aeronautical Engineering Technical Research Center,Beijing 100076,China;4.Research Institute of Aero-Engine, Beihang University,Beijing 102206,China;5.Beijing Key Laboratory of Aero-Engine Structure and Strength,Beijing 102206,China
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| Abstract: |
| Owing to the complex influence of the elevate temperature， external loads and long service time， the microstructural morphology of the Ni-based superalloy deteriorates inevitably， including coarsening and rafting of the γ' precipitates， which results in the reduction in low cycle fatigue （LCF） resistance of directional solidification （DS） and single crystal （SC） Ni-based superalloys. In order to predict the LCF life of the microstructure degradation superalloys， the worsening of fatigue resistance owing to the microstructure degradation is converted into that the superalloy suffers more severe loading under the standard heat treatment conditions， while the mechanism of the fatigue failure remain unchanged under specified loads. LCF prediction models considering the microstructure state were established and verified based on the continuous damage mechanics （CDM） and the strain energy density （SED） theory， respectively. The prediction results of the two models were verified by the experimental results of LCF tests on the coarsening / rafting DZ125 SC Ni-based superalloy carried out previously by us. The results indicate that the predicting results of the two models are in good agreement with the experimental results， and the predicting results are controlled within a three coefficient of scatter. The fatigue life prediction methods could effectively capture the microstructure deterioration of coarsening / rafting on LCF life of the alloy. Moreover， the fatigue performance evaluation of high temperature components is expanded from the traditional two-dimensional load-life plane to the microstructure degradation dimension including time effect. |
| Key words: Superalloy Microstructure degradation Low cycle fatigue Damage mechanics Strain energy density Life prediction |
