Microstructure in hydrogen induced cracking of pipeline steel

点击翻译按钮获取中文摘要

One of the most important damage modes in oil and gas pipeline steels is Hydrogen Induced Cracking (HIC) that is often associated with sulfide stress cracking SSC. This type of failure dominates in environment of hydrogen sulfide that is present in the natural gas and fluids transported in the pipe. HIC has been studied extensively, however the mechanisms of failure related to presence of sulfides and other nonmetallic inclusions is not yet sufficiently clear. The presence of hydrogen sulphide in natural gas and oil has lead to renew interest in development of steels that are more resistant to HIC and SSR related failure. In the proposed program, a detailed investigation of HIC will be carried on X-60 and X-65 pipeline steels manufactured by Evraz. The objective of the present project is to study the influence of microstructure of the steels on hydrogen ingress and distribution to establish a role that phases, precipitates, texture, grain interfaces play in HIC and SSC in the environment of stress and corrosion. The obtained results would help in identifying the steel structure that will improve the resistance to failure in sour gas and oil environment. The knowledge gained from the experiments will be used to build up microstructure based model that can help in predicting the hydrogen-induced failure behavior of steels. Novel methods of structural analysis by in situ orientation imaging under stress, mapping of phase composition, grain orientation, stress distribution, chemical composition and using hydrogen microprint to image hydrogen distribution in steels are expected to provide novel information that are relevant for understanding of the processes of nucleation and propagation of cracks. Synchrotron three-dimensional imaging of cracks propagation might offer new understanding of fracture process in hydrogen and sulfide environment. The results obtained will allow EVRAZ to consider modification of the manufacturing processes and to adopt strategy to mitigate HIC in pipeline steels this company produces.