Effect of local multi-axial stress on creep crack growth behavior in the heat affected zone

Abstract

Under the multi-axial stress field, creep crack growth is considered to occur in brittle manner. From the view point of practical use, it is important to conduct the characterizations of the creep crack growth rate and its life under the multi-axial stress field to predict the life of creep crack growth. In the present study, for the welded joint of the W-added 9Cr ferritic heat-resistant steel, ASME Code Case 2179/ASTM A335 P92, creep crack growth tests and 3-dimensional elastic-plastic creep finite element analyses were conducted to clarify the effect of stress multi-axiality on creep crack growth. As a result, the creep ductility of welded joint was found to decrease and shift to the creep brittle region as compared with that of base metal due to the large value of stress tri-axial factor TF.