Synergistic interaction of fatigue and stress corrosion on the corrosion fatigue crack growth behavior in Alloy 600 in high temperature and high pressure water

Three different types of cracking loads which simulate fatigue, stress corrosion cracking (SCC) and the combined fracture process of fatigue and SCC were applied to compact tension type Alloy 600 specimens in high temperature water at 290 C with 4 ppm dissolved oxygen concentration in order to evaluate the effects of various load applications on corrosion fatigue crack growth in Alloy 600. The measured crack growth rate of the specimen to which combined loads of fatigue and SCC were applied was faster than the predicted crack growth rate based on the superposition model. The increase in the crack growth rate indicates that there is a synergistic interaction of fracture processes at the growing crack tip which experiences combined loads of SCC and fatigue. So it is necessary to account for the acceleration due to the synergistic interaction of fracture processes in corrosion fatigue crack growth to conservatively predict the life of the structural components of Alloy 600 in corrosive nuclear environments. (orig.)