Application of nonlinear ultrasonic technique to characterize the creep damage in ASME T92 steel welded joints

This paper reports a novel use of nonlinear ultrasonic technique for characterizing the creep damage in ASME T92 steel welded joints. The creep tests of this joints were conducted at 650 °C/90 MPa for different times, to obtain specimens with different degrees of creep damage. After crept for 1560 h, the T92 steel welded specimen was fractured in fine-grained heat affected zone (FGHAZ), which indicates that the FGHAZ is the weakest zone of T92 steel welds. The nonlinear ultrasonic measurements were conducted after the creep test. The WM show a large original value of nonlinear parameter, but the variation of this parameter over creep time were relatively small compared with the BM and HAZ. The largest growth of nonlinear parameter occurs on the HAZ, which increased about 3 times in the creep fractured specimen compared with the original specimen. Meanwhile, metallographic examination indicates that the cavity growth is the main damage characteristic in FGHAZ. These results indicate that the nonlinear ultrasonic technique could be used to characterize the creep damage in ASME T92 welded joints.