基于热-结构耦合等离子喷涂热障涂层循环应力分布

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Aiming at the stress distribution in the depth direction of the TBCs and the influence of mechanical properties in heating, dwelling and cooling thermal cycles, the oxide layer surface was simplified to sine wave, thermo-mechanical coupled modeling of periodic boundary conditions of air-plasma-sprayed （APS）thermal barrier coatings （TBCs） on Ni-based alloy was investigated. In the computational models, nonlinear relationships （e.g., convective heat transfer between surrounding environment and coatings, and thermal transfer between the different layers etc.）were considered in the modeling. After the analysis of residual stress influenced by coating creep, the stress redistributed as the change of the thickness of oxide layer, and the results of the cycle and the separate cooling process were compared. The results indicate that the stress significantly is reduced in the dwelling stage because of stress relaxation. The maximum stress occurrs in the peak at the BC/TGO interface and it is amplified at the cooling stage. Moreover, the internal stress in the BC and TGO layer has been increased,when TGO＇s thickness increased,whilst film adhesion had fallen sharply.针对等离子喷涂热障涂层在升温-恒温-降温过程中涂层应力沿层深分布情况及相关力学性能的影响,首先,将氧化层简化为正弦波形式,采用热-结构耦合瞬态计算周期边界条件,考虑了涂层系统上下表面与环境对流传热、涂层系统各层间热传导以及各层材料热机属性随温度变化等非线性关系,建立了热障涂层分析模型;然后,分析比较了涂层蠕变对残余应力的影响,以及随着氧化层厚度的变化,应力的再分布情况;最后,对循环过程与单独降温过程结果进行了比对。研究结果表明,由于恒温阶段蠕变的影响,应力大幅减小;应力增长主要集中在降温过程中,其中最大应力出现在氧化层与粘结层界面波峰处;随着氧化层厚度的增加,氧化层/粘结层内部拉应力显著增加,膜基结合力大幅下降,对涂层的稳定性产生影响。