Comparison of creep crack growth rates on the base and welded metals of modified 9Cr-1Mo steel

This paper is to compare Creep Crack Growth Rates (CCGR) on the Base Metal (BM) and Welded Metal (WM) of modified 9Cr-1Mo steel for Gen-IV reactors. Welded specimens were prepared by Shielded Metal Arc Weld (SMAW) method. To obtain material properties for the BM and welded metal, a series of creep and tensile tests was conducted at 600 .deg. C, and CCG tests was also performed using 1/2compact tension specimens under different applied loads at 600 .deg. C. Their CCGR behaviors were analyzed by using the empirical equation of the da/dt vs. C* parameter and compared, respectively. It appeared that, for a given value of C*, the rate of creep propagation was about 2.0 times faster than in the WM than the BM. This reason is that a creep rate in the WM was largely attributed when compared with that in the BM. From this result, it can be utilized for assessing the rate of creep propagation on the BM and WM of the G91 steel.