Nondestructive testing method for film coating debonding defect based on grating laser ultrasonic sound spectrum

Abstract

The invention discloses a nondestructive testing method for a film coating debonding defect based on a grating laser ultrasonic sound spectrum. The method comprises the following steps that a strong pulse laser beam is irradiated to a surface of a detected film coating structure through an optical mask plate or a microarray lens to form periodically distributed tiny grating-shaped laser spots, and ultrasonic waves with fixed wavelength are excited in a detected area; when the detected area has no debonding defect, the excited ultrasonic wave is a Rayleigh wave, and when the detected area has the debonding defect, a Lamb wave is generated; under the condition of certain wavelength, as the wave velocities of the two waves are different, the corresponding frequencies of the two waves are different, the laser ultrasonic detection unit is adopted to receive the generated ultrasonic signals near the detected area, the center frequency of the ultrasonic signals is obtained, and whether the debonding defect exists or not can be judged according to a center frequency value of the detected signals; and the size of the debonding defect can be judged through scanning detection, and the debonding defect can be imaged.

Description

technical field [0001] The invention relates to a nondestructive detection method for debonding defects of coatings, in particular to a nondestructive detection method for debonding defects of thin film coatings based on grating laser ultrasonic sound spectrum. Background technique [0002] The coating is a solid continuous film structure sprayed on the surface of the substrate material for the purpose of protection, heat insulation and wear resistance. It is widely used in high-temperature structural components such as aero engines and heavy gas turbines. It is deposited on high-temperature resistant alloy substrates The surface of the material reduces the operating temperature of the component and prolongs its service life. However, in the long-term service process, the internal debonding defect of the coating system (coating + substrate) is an important cause of coating failure. As the working time of the coating increases, debonding defects will initiate and expand insi...

AI Technical Summary

Problems solved by technology

When the traditional ultrasonic testing method detects the debonding defect of the coating, the body wave is generally used to detect the debonding defect. This method will cause signal confusion between the initial wave and the reflected wave when the coating is thin. Difficult to distinguish, resulting in surface blind spots in the detection of coating debonding defects, and effective detection of debonding defects in thin film coatings. At the same time, there are several shortcomings such as the inability to achieve complete non-contact measurement, and the inability to realize detection in harsh environments such as high temperatures. , resulting in many limitations in the current detection process of coating debonding defects

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