Microstructure in hydrogen induced cracking of pipeline steel

油气管线钢中最重要的破坏形式之一是氢致开裂(HIC)，它往往与硫化物应力开裂有关。这种类型的故障主要存在于天然气和管道中输送的流体中存在的硫化氢环境中。HIC已经得到了广泛的研究，但与硫化物和其他非金属夹杂物的存在有关的失效机制还不够清楚。天然气和石油中硫化氢的存在重新引起了人们对开发更耐HIC和SSR相关失效的钢的兴趣。在拟议的计划中，将对Evraz生产的X-60和X-65管线钢进行详细的HIC调查。本项目的目的是研究钢的微观组织对氢的进入和分布的影响，以确定相、析出物、织构、晶界在应力和腐蚀环境中在HIC和SSC中所起的作用。所获得的结果将有助于识别将提高钢结构在酸性气体和石油环境中的抗破坏能力。实验所获得的知识将被用来建立基于微观组织的模型，该模型可以帮助预测钢的氢致失效行为。通过应力作用下的原位取向成像进行组织分析、绘制相组成、晶向、应力分布、化学成分以及利用氢显微指纹成像氢在钢中的分布的新方法有望为理解裂纹的形核和扩展过程提供新的信息。裂纹扩展的同步辐射三维成像可能会对氢和硫化物环境中的断裂过程提供新的理解。所获得的结果将使Evraz能够考虑修改制造工艺，并采取战略来减少该公司生产的管线钢中的HIC。

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.