Effect of stress on lead induced stress corrosion cracking of Inconel Alloy 690TT steam generator tube

This study systematically investigated the effect of stress levels on the lead-induced stress corrosion cracking (PbSCC) behavior of Alloy 690TT in high temperature lead-containing caustic solution using the C-ring stress corrosion test method. Results demonstrated that although high stress level did not change the initiation time, it significantly increased the probability of crack initiation. Furthermore, during the crack propagation stage, the high stress level greatly accelerated the crack growth rate, resulting in a higher number of cracks and greater crack lengths. Microscopic mechanism analysis revealed that lead deposited at the metal-oxide interface, inhibiting repassivation and promoting the selective dissolution of Cr and Fe, thereby leading to the formation of a brittle Ni-rich zone. This process followed the mechanism of lead-induced repassivation inhibition-dealloying embrittlement. High stress increased the probability of crack initiation by exacerbating local plastic deformation to damage the oxide film and by acting synergistically with lead, and then drove rapid crack propagation by subsequently promoting the micro-fracture of the brittle dealloying zone. This study revealed the critical role of stress in the PbSCC process and provided an important theoretical foundation for assessing the long-term service safety of Alloy 690TT under complex stress conditions.