Investigation of Fatigue Crack Propagation Behavior on the Surface of Machining Notches of Alloy 690TT in Simulated Pressurized Water Reactor Water

The fatigue crack propagation behavior on the surface of machining notches of Alloy 690TT (thermally treated) was investigated in room-temperature air environment and in simulated pressurized water reactor (PWR) environment with saturated air at 325°C. The results showed that more than one crack formed on the notch surface and the crack propagation paths were transgranular with some branching. The grain size also had some effect on the crack propagation path but had no significant effects on the crack growth rates (CGRs). The CGR vs. a curve could be divided into two stages in air environment and three stages in simulated PWR environment. The corrosive environment promotes crack propagation in the macroscopic crack propagation stage. Different load frequencies express similar crack propagation process, but decreasing frequency can assist the corrosion fatigue crack nucleation and propagation on the notch surface.