Abstract
In this study, hydrogen-induced cracking (HIC) and sulfide stress corrosion cracking (SSC) behaviors of high-strength pipeline steels in four different strength grades (X70, X80, X90 and X100) with the microstructure of acicular ferrite were estimated. The results showed that both of X70 and X80 steels exhibited better HIC resistance, and their susceptibility to HIC increased with the strength grade. HIC parameters, including cracking length ratio, cracking thickness ratio (CTR) and cracking sensitivity ratio, were all increased, and among these, the CTR increased most, with the increase in the strength grade. HIC was found to initiate and grow along the hard boundaries such as large size martensite/austenite (M/A) islands and bainitic ferrite. In addition, the density of hydrogen-induced blister on the steel surface was increased with the decrease in pH value for the same-grade pipeline steels. SSC susceptibilities of X80, X90 and X90-C were revealed to subsequently decrease, which was related to the large size M/A islands.
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