Creep degradation assessment in 9%Cr heat-resistant steel welded joints using ultrasonic methods

Abstract

The assessment of creep degradation in a 9%Cr heat-resistant steel welded joint has been carried out by means of nonlinear ultrasonic and traditional linear ultrasonic technique. The ultrasonic measurements were conducted at several regions of welded joint, which include the WM, HAZ, and BM. The experimental results indicate that, as creep time extends, the nonlinear parameter show a general upward trend in each region, and the largest increase of nonlinear parameter occurred on the HAZ. Meanwhile, the longitudinal wave velocity did not reveal a regular change in the welded joint, and the ultrasonic attenuation in HAZ only distinctive at the late stage of the creep life. These results reflect that nonlinear ultrasonic technique could be used to evaluate the creep degradation in 9%Cr steel welded joints at the early stage, which could make up the disadvantages of the traditional linear ultrasonic method. Keywords: Ultrasonic technique, Creep damage, 9%Cr steel welded joints