Combined effects of nano-precipitates and cold work on the SCC growth behavior of alloy 718

The stress corrosion cracking (SCC) propagation behavior of cold worked Alloy 718 subjected to different post-heat treatments was investigated in oxygenated high temperature water at 325°C. The results show that cold work significantly accelerated SCC propagation, with crack growth rates (CGRs) on the order of ∼10 –6 mm/s, whereas both post-heat treatments reduced the CGRs by approximately 35-40 times to the order of ∼10 –8 mm/s. The reduced CGRs after post-heat treatments are associated with partial relief of residual strain and the suppression of slip system by nano-precipitates, which may alleviate the strain field of crack tips. Electrochemical measurements revealed no consistent correspondence between galvanic corrosion behavior and SCC crack growth behavior, suggesting that galvanic corrosion alone is unlikely to be the primary factor controlling SCC propagation.