EB-PVD热障涂层系统界面应力的理论分析

Analytic Research on Interface Stress of EB-PVD Thermal Barrier Coatings

目的获得热障涂层系统危险界面应力解析解及其变化规律。方法基于弹性理论,推导出能同时考虑氧化物热生长及其形貌、CaO-MgO-Al2O3-SiO2(CMAS)沉积、温度变化、材料参数不匹配的危险界面应力分布的解析解。分别研究热循环中氧化层热生长和CMAS沉积对热障涂层界面应力的影响,并从应力演化的角度对危险界面微裂纹的萌生和扩展进行预测。结果理论分析显示,当系统经历24个热循环后,陶瓷层/氧化物层界面波谷应力σv从最初的0增加到301.44MPa。氧化物层/粘结层界面波峰应力σp从最初的617MPa增加到1189.89MPa。当CMAS沉积深度hCMAS从0增加到150μm时,应力σv从170.26MPa增加到443.37 MPa,应力σp从1317.83 MPa减小到1050.17 MPa。结论氧化物热生长可以促使陶瓷层/氧化物层界面波谷和氧化物层/粘结层界面波峰裂纹的萌生和扩展。CMAS沉积将进一步促使陶瓷层/氧化物层界面开裂,然而对氧化物层/粘结层界面的开裂有抑制作用。解析解的计算结果与先前的有限元分析结果和模型试验结果相近,证明了该理论方法计算界面应力的准确性。

The paper aims to obtain the analytic solutions of distribution of stress in critical interfaces and their change laws.The analytic solutions of distribution of stresses in critical interfaces were obtained based on theories of elastic mechanic,which could take into account the growth of thermally grown oxide(TGO),TGO morphology,Ca O-Mg O-Al2O3-SiO2(CMAS)deposition,change of temperature and the misfit of material parameters.The effects of thermal growth of oxide layer and CMAS deposition on the evolution of interface stress in thermal barrier coatings during thermal cycles were researched,and the initiation and propagation of cracks at critical interfaces were predicted from the stress evolution.After TBCs experienced 24 thermal cycles,the stressσv at the valley of top coating(TC)/TGO interface increased from 0 to 301.44 MPa.The stressσp at the peak of TGO/bond-coat(BC)interface increased from 617 MPa to 1189.89 MPa.When the hCMAS of CMAS deposition increased from 0 to 150μm,the stressσv increased from 170.26 MPa to 443.37 MPa,and the stressσp was reduced from 1317.83 MPa to 1050.17 MPa.The TGO growth would promote crack initiation and propagation at the valley of TC/TGO and at the peak of TGO/BC interface.The CMAS deposition would further promote crack initiation and propagation at the valley of TC/TGO interface but suppress crack initiation at the peak of TGO/BC interface.The calculated results of the method proposed were observed to mutually agree with the previous research results obtained by finite element method and model test results.It is proved of accuracy to calculate the interface stress with this theoretical method.