Microstructure in hydrogen induced cracking of pipeline steel

油气管线钢最重要的损伤模式之一是氢致开裂（HIC），它通常与硫化物应力开裂SSC有关。这种类型的故障主要存在于管道中输送的天然气和流体中的硫化氢环境中。HIC已被广泛研究，然而，与硫化物和其他非金属夹杂物的存在相关的失效机制尚未足够清楚。硫化氢在天然气和石油中的存在导致了对开发更耐HIC和SSR相关失效的钢的重新兴趣。在拟议的计划中，将对Evraz生产的X-60和X-65管线钢进行HIC的详细调查。本项目的目的是研究钢的微观结构对氢进入和分布的影响，以确定相、沉淀物、织构、晶粒界面在应力和腐蚀环境中的HIC和SSC中的作用。所获得的结果将有助于确定钢结构，将提高耐故障的酸性气体和石油环境。从实验中获得的知识将被用来建立基于微观结构的模型，可以帮助预测氢致失效行为的钢。通过应力下的原位取向成像、相组成、晶粒取向、应力分布、化学组成的映射以及使用氢微印来成像钢中的氢分布的结构分析的新方法预计将提供与理解裂纹的成核和扩展过程相关的新信息。裂纹扩展的同步辐射三维成像可能为氢和硫化物环境中的断裂过程提供新的认识。所获得的结果将使EVRAZ考虑修改生产工艺，并采取战略，以减轻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.