A preliminary study on hydrogen pipeline: Macro-, micro-, nano-mechanical behavior of hydrogen-charged API linepipe steels

Abstract

With a viewpoint of industrial field applications, one of the important topics, which are being studied to prepare the up-coming `hydrogen economy era,` is hydrogen transmission. Pipeline is conceivably the most economic way to consistently and safely transport a large amount of hydrogen over a long distance, which may be strongly requested in hydrogen economy era. Although hydrogen pipelines have already been operating over the past 50 years, they are still very limited (e.g., only 1300 miles in Europe and US) and designed for low service pressure. So, the development of advanced high-pressure `hydrogen pipeline (HP)` is highly desirable. As a good starting point for the purpose, one might wonder whether existing natural gas pipelines (mainly made of API steel) can be used as the hydrogen pipeline or not. To gain an insight to answer the question, here we performed a series of macro-, micro-, nano-scale mechanical tests (including tensile test, Charpy impact test, micro-Vickers hardness test, and instrumented micro-/nano-indentation) on hydrogen-charged API X65, X70 and X100 linepipe steels having different strength level. From the experimental results together with microstructural observations, the influence of hydrogen on the mechanical behavior in the API steels are systematically analyzed and discussed.