Hydrogen charging effect on the stress corrosion cracking of Alloy 690 tubes with dents in a lead-containing high temperature caustic environment

● Alloy 690 exhibits susceptibility to stress corrosion cracking (SCC) under lead-containing high temperature and high pressure (HTHP) caustic environment. ● H accelerates the initiation and propagation of SCC mechanically. ● H changes the oxidation process in SCC chemically. ● The relationship between Von Mise Stress and crack depth for both original and H charging samples is established. Abstract The effect of hydrogen (H) on the stress corrosion cracking (SCC) of Alloy 690 with dents in a lead-containing high-temperature and high-pressure (HTHP) caustic environment is thoroughly analyzed. Cracks are only found in dents in original samples, while cracks are present both inside and outside the dents after H charging. After H charging, kernel average misorientation (KAM) and geometrically necessary dislocation (GND) decrease near the crack. The oxide ahead of the crack tip disappears, and the extent of Cr 3+ oxidation in the oxide/crack becomes more extensive. The concentration of Pb at the oxide/matrix and oxide/oxide interfaces is higher, attributed to the fracture or decohesion of oxide and matrix after H charging. These results indicate that H exerts chemical-mechanical synergy effects on SCC. Based on the finite element simulation, the relationship between Von Mises Stress and crack depth is established. This offers experimental references and data support for SCC in Pb-containing HTHP caustic environments.