Abstract
Hydrogen-induced degradation, especially hydrogen-assisted fatigue, and fracture, must be carefully considered to maintain reliability and structural integrity of steel pipelines in gaseous hydrogen service. Additionally, the susceptibility of steels to hydrogen is well documented to be sensitive to the strength of the steel. Therefore, high strength pipeline steels with yield strength greater than 600 MPa, such as X100 and X120, must be evaluated to assess their susceptibility to hydrogen embrittlement. In this work, microstructure and mechanical properties, including the fatigue crack growth rate and fracture toughness in high-pressure hydrogen gas at a pressure of 1000 bar(105 MPa), of an as-received X120 steel were experimentally investigated. The results show the fatigue crack growth rates in gaseous hydrogen of this X120 steel follow the ASME design curves for hydrogen from the Boiler and Pressure Vessel Code Section VIII, Section 3 Code Case 2938-1. The fracture resistance in 1000 bar hydrogen gas is 43 MPa·m1/2, which is higher than approximately 30 MPa·m1/2 reported for Cr-Mo and Ni-Cr-Mo pressure vessel steels with the similar tensile strength level (approximately 950 MPa). Multi-scale metallurgical analyses were conducted to characterize the underlying microstructural features contributing to the higher fracture toughness of X120 compared to the Cr-Mo and Ni-Cr-Mo steels. The characterization shows a fine bainitic microstructure (grain size: 1 µm) and fewer carbides, characteristics created by the thermo-mechanically controlled processing (TMCP) and a lower carbon content, respectively. These features likely provide a higher fracture resistance in gaseous hydrogen compared to the traditional tempered martensitic microstructure of pressure vessel steels with greater carbon contents. A fractography analysis on the tested X120 specimens was also conducted to further reveal its fracture characteristics under high-pressure hydrogen gas. Both fatigue and fracture surfaces exhibit mainly quasi-cleavage cracks. Secondary cracks propagated in a mixed intergranular and transgranular mode. The fracture surface is much coarser and has deeper secondary cracks than that in the fatigue region.
| Original language | English |
|---|---|
| Title of host publication | Materials and Fabrication |
| Publisher | American Society of Mechanical Engineers (ASME) |
| ISBN (Electronic) | 9780791888506 |
| DOIs | |
| State | Published - 2024 |
| Event | ASME 2024 Pressure Vessels and Piping Conference, PVP 2024 - Bellevue, United States Duration: Jul 28 2024 → Aug 2 2024 |
Publication series
| Name | American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP |
|---|---|
| Volume | 4 |
| ISSN (Print) | 0277-027X |
Conference
| Conference | ASME 2024 Pressure Vessels and Piping Conference, PVP 2024 |
|---|---|
| Country/Territory | United States |
| City | Bellevue |
| Period | 07/28/24 → 08/2/24 |
Funding
This work is supported by the U.S. Department of Energy, through the Office of Energy Efficiency and Renewable Energy\u2019s ((EERE) Hydrogen and Fuel Cell Technologies Office (HFTO)\u2019s Hydrogen Materials Compatibility Consortium (HMat) Program. The research and development work was performed at the Oak Ridge National Laboratory and Sandia National Laboratories. Oak Ridge National Laboratory (ORNL) is managed by UT-Battelle LLC for the US Department of Energy under contract DE-AC05-00OR22725. The authors would like to acknowledge Dr. Qingqiang Ren (ORNL) and Dr. Yi Feng Su (ORNL) for the TEM characterization. This article has been authored by an employee of National Technology & Engineering Solutions of Sandia, LLC under Contract No. DENA0003525 with the U.S. Department of Energy (DOE). The employee owns all right, title and interest in and to the article and is solely responsible for its contents. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this article or allow others to do so, for United States Government purposes. The DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan https://www.energy.gov/downloads/doe-public-accessplan. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government.