Hydrogen Effects on Mechanical and Toughness Properties of Pipeline Steels

This paper reviews commonly used hydrogen charging methods and effects of hydrogen on Charpy toughnessToughness. Preliminary ex-situ Charpy testsCharpy test of electrolytically pre-charged specimens of three pipe steels were performed at room temperature. The gaseous hydrogen charging method is directly applicable to hydrogen pipelines but the lack of testing capability has limited its utilizations in R&D and qualification. The electrolytic charging method can be convenient and appropriate for investigating the effects of hydrogen especially if correlations between current density or potential and gaseous pressure are established. Preliminary experimental results have shown that the Charpy absorbed energy (CVN) of the electrolytically pre-charged specimens were lower than those of uncharged specimens by 8–20% for the steels investigated. Based on the load–deflection curves, the effects of hydrogen on Charpy toughnessToughness were to facilitate fracture initiation from the notch and accelerate fracture propagation after fracture initiation. In-situ Charpy and fracture toughnessToughness testing at slow rates would be more suitable for pipeline applications than impact testing.