基于超声声压反射系数相位谱法的热障涂层非均匀性表征

Ultrasonic Characterization for the Inhomogeneity of Thermal Barrier Coating Based on the Sound Pressure Reflection Coefficient Phase Spectroscopy

利用声压反射系数相位谱法对厚度为(50±5)μm,等离子体喷涂方法制备的Cr2O3陶瓷涂层的非均匀性进行了超声表征。对试样不同位置进行了声压反射系数幅度谱和相位谱测试分析,发现由相位谱测得的不同位置的声速值存在差异并且相位谱极值间的变化规律相反。结合扫描电镜(SEM)分析,认为这种差异是由涂层中孔隙与裂纹密集程度不同所引起的。借助数值计算,分析了涂层密度对相位谱的影响,进而解释了同一涂层试样相位谱极值间变化规律相反的原因。试验和数值计算结果表明,声压反射系数相位谱对涂层内部组织结构的变化更为敏感,可以用来表征涂层的非均匀性。

Phase spectroscopy of sound pressure reflection coefficient （SPRC） was used to nondestructively characterize the inhomogeneity of plasma sprayed Cr2O3 coatings with the thickness of （50 ± 5） μm. Analyses of amplitude spectroscopy and phase spectroscopy were carried out on the different locations of the coating. Then the velocities measured by amplitude and phase spectroscopy at the locations were obtained. It was found that the velocities measured by phase spectroscopy were different and the change laws between the extremum of phase spectroscopy were distinct. According to the observation of scanning electron microscope （SEM）, the differences were attributed to microstructure differences caused by the difference of microstructure caused by the various distributions of porosity, and microcracks. The influence of density on phase spectroscopy was discussed for explaining the differences of the shape of spectroscopy between the variant positions on the same sample, based on the method numerical calculation. Moreover, the results of experiment and numerical calculation showed that ultrasonic phase spectroscopy itself was a good indicator to reveal differences between density and microstructures of coating prepared by the method of plasma spray.