Microscopic damage laser ultrasonic identification of metal pipelines in high temperature and high pressure service environment

Identifying metallographic microstructure damage on the surface of metal pipelines in high-temperature and high-pressure service environments is a major technical challenge. Laser ultrasonic technology was used to identify the spheroidized microdamage of 12Cr1MoV pipelines, and a method for identifying the pearlite proportion using surface wave acoustic parameters was obtained. Three pearlite proportion identification models were established: the surface wave velocity method, attenuation coefficient method, and wavelet packet energy characteristic method. 12Cr1MoV specimens with different degrees of spheroidization were prepared using solid solution heating, and the pearlite proportion of the specimens was extracted using ImageJ software to quantitatively evaluate their spheroidization grade. Test results showed that the comparison errors between the model-predicted values of the three pearlite proportions and the values extracted by ImageJ software were 8.15%, 13.03%, and 6.04%, respectively. Laser ultrasonic technology could effectively identify the metallographic microstructure on the surface of metal pipelines in high-temperature and high-pressure service environments.