Combined Effect of Hydrogen and Dynamic Strain Aging on Low Cycle Fatigue Behaviors of SA508 Gr.1a Low Alloy Steels in 310 .deg. C Deoxygenated Water

Significant reduction of fatigue life of structural materials in nuclear power plants is one of the issues of considerable significance to maintain superior integrity throughout their service life. From extensive studies, hydrogen induced cracking (HIC) is widely accepted mechanisms for reduction of fatigue life of low alloy steels (LAS) used as structural materials. Some of authors reported that hydrogen content in reactor pressure vessel could reach 2 ∼ 5 ppm during reactor operation. Hydrogen was resulted from corrosion reaction at the metal surface or crack tip in water. In addition, it has been reported that LAS is susceptible material for dynamic strain aging (DSA) in PWR environment at specific strain rate. Therefore, it is possible that the synergism between DSA and hydrogen might induce more significant LCF damage in PWR environment. In this regard, combined effect of DSA and hydrogen was investigated in this study. For that, LCF tests of SA508 Gr.1a LAS in various environments and tensile tests of hydrogen charged (H charged) samples in DSA range were conducted