考虑孔隙细观特征的热障涂层脱粘缺陷超声检测数值模拟

Ultrasonic Testing Numerical Simulation of Debonding Defect in Thermal Barrier Coatings Considering Void Microscopic Parameters

为探究孔隙细观形貌对热障涂层脱粘缺陷超声检测定量精度的影响,基于电子束物理气相沉积法制备的厚度约为100μm的ZrO_2-7%Y_2O_3(7YSZ)热障涂层SEM形貌,建立了界面脱粘尺寸0.2~2.0 mm、孔隙率范围0%~5%、孔隙平均宽高比分别为4∶10、6∶10、8∶10和10∶10的多组热障涂层二维随机孔隙模型(Random void model,RVM),采用时域有限差分技术进行了超声检测数值模拟。结果表明:当涂层厚度一定时,涂层声压反射系数幅度谱极值与脱粘尺寸呈线性关系,脱粘尺寸超声定量误差随孔隙率和孔隙平均宽高比的增加而增大,当涂层孔隙率为5%时,超声测量最大相对误差已达到37.7%,孔隙平均宽高比增大为10:10时,超声测量最大相对误差达到36.9%。此外,由于受孔隙分布状态的影响,超声定量结果呈现出一定的波动性。

To investigate the effect of void microscopic parameters （porosity, distribution and morphology of void） on the quantitative accuracy of ultrasonic testing for thermal barrier coatings debonding defect, several two-dimensional TBCs random void models （RVM） with 0.2？2.0 mm length of debonding, 0%？5% of porosity, and 4：10, 6：10, 8：10, 10：10 of void aspect ratio were built based on the SEM morphologies of the ZrO2-7%Y2O3 （7YSZ） coating with about 100 μm thickness deposited by electron beam physical vapor deposition. The numerical simulation was carried out based on finite-difference time-domain method. The simulation results show that the extreme values of the ultrasonic reflection coefficient amplitude spectrum are related linearly to the length of debonding defect when the coating thickness is unchanged. The ultrasonic measurement errors of debonding length gradually increase with the increase of porosity and aspect ratio of void. The maximum relative errors reach 37.7% and 36.9%, respectively, when the porosity is 5% and the void aspect ratio increases to 10：10. In addition, the ultrasonic measurement results fluctuate according to different void distributions.