Study on Stress Corrosion Cracking of X100 Pipeline Steel in NS4 Solution

The X100 pipeline steel is classified as a type of high-strength, low-alloy steel that is mostly used in the construction of pipelines designed for the extensive transit of natural gas and oil. Although X100 steel has exceptional mechanical qualities, it is vulnerable to stress corrosion cracking (SCC) when exposed to specific environmental conditions. Stress corrosion cracking has the potential to induce the development of minute fissures on the steel surface, which then propagate throughout the material, ultimately resulting in structural failure. The microstructure and electro-corrosion phenomena were investigated by the utilization of scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and polarization curves. Additionally, the susceptibility to stress corrosion cracking was assessed by analyzing the mechanical properties and cross-sectional characteristics utilizing interrupted slow strain rate testing (SSRT) techniques. Upon examining X100 steel, the granular bainite structure of the ferrite and martensite–austenite (M–A) components was observed. Overall, the average corrosion rates were 7.57 mpy. The main cracks occurred laterally and perpendicular to the direction of applied tension, whereas secondary cracks occurred almost to the point of cross-sectional fracture, demonstrating X100 susceptibility to SCC in NS4 solution.