Rate Controlling Steps of SCC of High Strength Steels Available to Purchase

Stress corrosion crack velocities have been measured for a high strength steel in 0.5N NaCl solution at room temperature without potentiostatic control. Changing the strength level of the steel alters the shape of the SCC velocity vs stress intensity curve distinctly. With increasing strength, the common plateau region (so called stage II) disappears, and SCC velocity becomes exponentially dependent on stress intensity. Additional experiments (acoustic emission studies, crack growth incubation measurements, load change tests, fractography) confirm the current understanding, that absorbed hydrogen is the damaging species. The results can be well interpreted by assuming that lattice decohesion of the metallic bonds by absorbed hydrogen is a fundamental feature of the cracking process. Conclusions can be drawn as to the rate controlling steps of crack growth.