Effect of Cyclic Strain Rate and Sulfides on Environmentally Assisted Cracking Behaviors of Sa508 Gr. 1a Low Alloy Steel in Deoxygenated Water at 310℃

Environmental Fatigue of Metallic Materials in Nuclear Power Plants – A Review of Korean Test Programs

“…As mentioned above, the LCF life of LASs in 310 ºC deoxygenated water is affected by hydrogen [8]. Because hydrogen is known to play the role of a softener in the DSA temperature range [14,15], it could be closely related to the reduction of the cyclic stress in 310 ºC deoxygenated water.…”

“…6 water was affected by environmentally assisted cracking (EAC) mechanisms such as metal dissolution and hydrogen induced cracking (HIC) [8]. On the fatigue surface of the specimens tested in 310 ºC deoxygenated water, the streamed down features of fatigue striations and a blunt shape of a crack tip were observed, which are considered as traces of metal dissolution mechanism [8]. In addition, the brittle cracks and micro-cracks ahead of the crack tip were observed in specimens tested in 310 ºC deoxygenated water, which are known as the evidence of HIC mechanism.…”

“…The high hydrogen concentration at the crack tip would be formed due to the stress gradient and enhance the strain localization [9,10]. Thus, the initiation and the growth of micro-cracks could be accelerated by HIC [8]. Therefore, the main EAC mechanisms for the reduction of LCF life in 310 ºC deoxygenated water could be the metal dissolution and HIC.…”

“…Therefore, like SA508 Gr. 1a [8] and 316LN [19,20], the LCF life of CF8M was mainly affected by the environmental factor during LCF processes in 310 ºC deoxygenated water [22].…”