Effect of Thermal Aging on Fatigue Crack Growth Behavior of A 533 B Pressure Vessel Steel Under High Temperature Water

摘要

The fatigue crack growth behavior of A 533 B steel which was subjected to PWHT and step- cooling heat treatments was examined in a simulated BWR water environment and in air. The test variables investigated included thermal aging effect, frequency variation over the range 0.05 to 0.5 Hz, and R-ratios of 0.1 and 0.5. The physical and metallographic examinations were carried out using transmission and scanning electron microscopes, and Auger spectroscopy. The results show that the thermal aging such as the step-cooling has no noticeable effect on the fatigue crack growth behavior both in air and 288℃ water environment. The crack growth rate in 288℃ water environ- ment is accelerated when frequency decreased and stress ratio increased. The acceleration of the crack growth rate may be due to occurrence of quasi-cleavage associated with hydrogen embrittle- ment.