Hydrogen sulfide (H₂S) stress corrosion cracking studies were conducted within the framework of fracture mechanics for several high strength steels (AISI 4340, 4140, HY-80, and HY-130). For all the steels and strength levels investigated (σys = 80 to 150 ksi), H²S stress corrosion cracking was found to exist. For each of the alloys investigated, a valid plane strain K_Iscc (which indicates the demarcation between detectable rates of crack extension, Δa/Δt ⩾ 10^-5 in./min and those below these rates) was measured and found to depend significantly on yield stress with decreasing K_Iscc values reported for increasing yield stress.

A limited investigation of crack growth kinetics found crack growth rates to accelerate most rapidly from presharpened fatigue cracks when loaded to K levels just beyond the K_Iscc threshold. In several instances, especially with the highest strength alloys, stress corrosion crack velocities attained peak values before being “damped” to some steady state velocity at increased K levels. The crack velocity damping might in part be attributed to crack division or plasticity effects associated with increasing plastic zone size to thickness ratio at higher K levels.