Sensing Signal Analysis and Imaging Processing with High Frequency Ultrasonic Testing for Fe-Based Amorphous Coatings

In harsh environments, Fe-based amorphous coatings can provide effective protection for equipment. A method of thickness measurement of thin layer and quality evaluation based on high-frequency water-immersion ultrasonic testing and imaging is proposed here. In this paper, because of the interface echoes of the micron-scale coating in the aliasing of ultrasonic testing signals, wavepacket decomposition and extraction technology proposed according to the matching pursuit theory is used to separate the interface echoes. After using the narrow pulse replacement method, the coating structure imaged is reconstructed. The decomposed interface echoes will not be mixed again, thus reflecting the coating thickness information more accurately. Consequently it can be used to evaluate the coating quality. Finally, the experimental results show that the coating structure image can be reconstructed after the high-frequency water-immersion ultrasonic scanning signals are processed with the above method. The relative error of the coating thickness detection is only 3.13% compared with the scanning electron microscope (SEM) results. At the same time, the coating spraying quality can be evaluated effectively through the imaged results.