涡轮叶片热障涂层减薄缺陷的微波扫频定量检测

Microwave frequency sweeping quantitative determination of thinning defect in thermal barrier coatings of turbine blades

热障涂层(TBC)是提高涡轮叶片耐热性能的有效手段之一。由于工作环境复杂、恶劣,TBC易遭受环境沉积物的冲刷侵蚀而形成减薄缺陷,造成其厚度降低甚至剥落,导致叶片结构失效,因此对TBC减薄缺陷进行有效无损定量检测非常重要。基于微波扫频反射方法,结合同轴探头,在26.5~35 GHz的频段下,对不同厚度TBC试样进行定量检测,细致探究微波检测信号与TBC减薄缺陷尺寸间的映射关系。通过仿真和实验研究,在频域和时域中,提出了微波检测信号特征提取方法,建立了检测信号特征与TBC厚度间的关联规律。研究表明:采用所提方法对TBC减薄缺陷实施定量检测,检测分辨率可达30μm。

The thermal barrier coating(TBC)is deemed as one of the effective means for enhancement of the heat resistance of turbine blades.Due to complex and harsh working environment,TBC are vulnerable to the thinning defect due to the erosion by environmental sediments,leading to the decrease in TBC thickness or even peeling.This will cause the structural failure of the turbine blades.Therefore,it is important to detect on thinning defect in TBC through effective nondestructive quantitative determination.Based on microwave frequency sweeping reflectometry method,in the frequency band from 26.5 GHz to 35 GHz combining with coaxial probe.Thermal barrier coating sample in various thicknesses is tested quantitatively.Relationship of mapping between testing signal and size of TBC thinning defect is investigated.Through simulations and experiments,the method for features extraction of signal microwave testing signal is proposed both in frequency and time domains.The relation rule between the detecting signal feature and TBC thickness is established.It is found by research that the proposed method is used to conduct quantitative determination of TBC thinning defect,the detection resolution can reach up to 30μm.