To evaluate the CCG behavior of the SMAW weldment of Gr. 91
steel, a series of creep and creep crack growth tests was carried out
under different applied loads at 600 C. Creep crack growth laws for
the BM, WM, and HAZ were constructed using the empirical
equation of da/dt vs. the C* parameter and compared. Results
showed that in the CCGRs, the BM and HAZ were similar, but the
BM was lower than WM and HAZ. TheWM and HAZ were found to
be about 2.0 times faster in the CCGR than the BM. This reason was
closely related to the higher creep strain rate in theWMand HAZ. It
was identified that lower creep strength existed in the HAZ of
welded joints. Thus, in welded joints of Gr. 91 steel, creep cracks
will dominantly initiate in the HAZ, because the creep life (or
strength) in the HAZ was significantly decreased compared with
the BM.