Time-dependent crack growth behavior for a SMAW weldment of Gr. 91 steel

This paper presents the experimental results on creep crack growth (CCG) behavior for BM, WM and HAZ in the weldment of Gr.91 steel, which was prepared by a shield metal arc weld (SMAW) process. A series of CCG data was obtained by the creep and creep crack growth tests under different applied loads for BM, WM and HAZ in Gr. 91 welded joint at 600 °C. The CCG behaviors were characterized by the empirical equation of the da/dt vs. C∗ fracture parameter, and the CCG laws for the BM, WM and HAZ were constructed and compared, respectively. Results showed that for a given value of C∗, the WM and HAZ were almost equal, but they were about two-times faster in the CCGR curves than the BM. This reason is that the CCGRs were closely attributed to their creep strength and creep strain rates. It is thus supposed that creep cracks will dominantly initiate in the HAZ, because lower creep strength existed in the HAZ compared with BM.