Total focus ultrasonic testing of main pipe weld with stainless steel surfacing layer

To solve the problem that structural noise interferes the defect identification of main pipe weld with stainless steel surfacing layer by ultrasonic testing, the total focusing method (TFM) is carried out by experiments in this paper. Taking the side-drilled hole with 2 mm diameter and 65 mm internal depth in the surfacing layer as an example, the TFM imaging results show that the signal-to-noise ratio increases by 5.3 dB and the array performance indicator decreases by 35% when the number of array elements are increased from 16 to 64. On this basis, phase coherence imaging (PCI) is introduced to weight the TFM image. PCI method can effectively improve the signal-to-noise ratio and image resolution. Compared with the original TFM images, signal-to-noise ratio increases by 13.19 dB and array performance indicator decreases by 65% for the image obtained by 64 elements.