The effect of nano-sized precipitates on stress corrosion cracking propagation of Alloy 718 under constant loads in PWR primary water

• Published in: Corrosion science 2025-01, Vol.242, p.112577, Article 112577
• Main Authors: Wang, Jiamei, Zhu, Tianyu, Wu, Yule, Chen, Kai, Guo, Xianglong, Ren, Quanyao, Li, Yuanming, Tang, Chuanbao, Yi, Hongpu, Ye, Liang, Xu, Shihao, Zhang, Jing, Tian, Wenxi, Zhang, Lefu
• Format: Article
• Language: English
• Subjects: Alloy 718; Crack growth rate; Precipitates; Stress corrosion cracking; TEM; TKD
• ISSN: 0010-938X
• DOI: 10.1016/j.corsci.2024.112577

The stress corrosion cracking (SCC) propagation behavior of solution-annealed and precipitation-hardened Alloy 718 was investigated. The results show γ″ and γ′ precipitates are beneficial on retarding its crack growth under constant loads. Nano-sized precipitates at grain boundary (GB) tend to impede GB migration and oxidation beyond the crack tip, thereby compensating for the detrimental effect of a steeper strain gradient resulting from prominent elevated yield strength. The observed 2–40 times increase in CGR in hydrogenated water (near the Ni/NiO boundary) primarily attributes to the preferential GB oxidation and instability of the oxides during phase transition. •The ultra-fine dispersed γ″ and γ′ precipitates results in a 3.5-fold enhancement in yield strength and a one-third reduction in ductility.•The ultra-fine dispersed precipitates have limited effect on corrosion behavior and does not accelerate SCC crack growth.•Nano-sized precipitates tend to impede GB migration and oxidation beyond the crack tip, thereby balancing the detrimental effect of a steeper strain gradient from elevated yield strength.•The SCC CGRs of Alloy 718 are approximately 2–40 times higher in hydrogenated water (near the Ni/NiO boundary) than in oxygenated water at 325ºC.