Experimental and numerical investigation of stress corrosion cracking in AISI 4340 steel under near neutral solution conditions

Stress Corrosion Cracking (SCC) poses a significant challenge in the oil and gas pipeline industry, jeopardizing pipeline integrity and posing risks to both the environment and human life. This research applies simulative finite element analysis (FEA), based on phase field modeling (PFM), and experimental methods to analyze the influence of applied potential on corrosion rate in simulated near neutral soil solution (NS4), utilizing Slow Strain Rate Testing to investigate the role of electrochemistry in SCC under NS4 solution conditions. Smooth round tension specimens were employed in the experiments, with data acquisition and logging facilitated through a condition-based monitoring system. The obtained results include stress-strain curves observed across various experimental conditions, along with detailed discussions on Tafel plots highlighting the effects of different applied potentials on time-to-failure, and the results showed that the time-to-failure of the material increased when the applied potential is decreased lower than the corrosion potential, which is noted to decrease the time-to-failure from roughly 7.25 days at normal conditions and no corrosive solution to roughly 5.12 days at -2000 mV. And it is noted that an increase of the applied potential to a certain value over the corrosion potential would increase the life of the material to 7.40 days at +400 mV, this increase requires further investigation. An FEA model was developed to predict the electrochemical behavior of the material and assess the impact of applied potential on material properties, aiding in the design of materials and structures resistant to stress corrosion cracking. The PFM model findings showed agreement with the experimental results, in terms of the stress-strain curves, the change in the corrosion rate, and the material time-to-failure. The findings have the potential to inform the development of preventive measures against SCC in pipeline systems, leading to lifesaving interventions and environmental damage prevention. Furthermore, the study emphasizes the reliability and importance of utilizing slow strain rate testing as an effective approach for investigating SCC in AISI 4340 steel alloys.