Creep-fatigue crack growth behavior of G115 steel under different hold time conditions

The creep-fatigue crack growth behavior and fracture mechanisms of G115 steel at 650 °C were studied using compact tension specimens in a constant load control mode. The crack growth length and load-line displacement analyses reveal that G115 steel is a creep-ductile material and the crack growth life and initiation time increase with increasing dwell time. Meanwhile, the parameter ΔK was used to characterize the crack growth behavior and the effect of dwell time on da/dN depends on ΔK. These data were also compared with those getting from P91 steel under 625 °C and P92 steel at 630 °C. When the crack growth rate, da/dtavg, is represented by Ctavg, all the data seem to collapse within a single narrow scatter band. Further, the approximate Nikbin-Smith-Webster (NSW) crack growth model was utilized to predict the creep-fatigue crack propagation behavior of G115 steel. And the microstructures of the cross-sections along the crack growth direction were studied through scanning electron microscopy to reveal the crack growth mechanisms of G115 steel.