Effects of hydrogen and strain rate on stress corrosion cracking mechanism of high strength pipeline steel

Hydrogen considerably affects the stress corrosion cracking (SCC) susceptibility of high-strength pipeline steel. The SCC mechanism of verification phase X100 steel, which can withstand higher transport pressures and reduce equipment weight, was studied by performing slow strain rate test (SSRT) tests at different strain rates and hydrogen pre-charging times. The results show that hydrogen pre-charging forms numerous microcracks inside the sample, which then join under tensile stress and lead to internal structural defects inside the material. Additionally, hydrogen atoms promote crack propagation by increasing the local dissolution rate at the crack tip, which significantly improves the SCC susceptibility. The strain rate indirectly alters the process for ion exchange between sample and solution medium, this ultimately alters the rate of electrochemical corrosion at the crack tip. X100 steel demonstrated the highest SCC susceptibility when the growth rate at the crack tip was comparable to the anodic dissolution rate.