Fractography of Hydrogen-Charged X70 Pipeline Steels under Quasi-Static Tension
Published in EUROCORR 2023, Brussels, Belgium, 2023
Keywords: Hydrogen embrittlement; Pipeline steels; Fractography; Welds; Quasi-static tension; Microstructure
Overview
This conference paper explores the effects of hydrogen charging on the fracture behavior of X70 pipeline steels under quasi-static tension. The study addresses hydrogen embrittlement challenges relevant to the repurposing of natural gas pipelines for hydrogen transport in the energy transition.
Research Objectives
- Characterize the microstructure and hydrogen uptake in X70 steels and welds
- Evaluate mechanical response under hydrogen charging
- Investigate fracture features in base metals and weld zones
- Link microstructural heterogeneities to embrittlement mechanisms
Methodology
- Microstructural characterization of base metals and welds
- Electrochemical hydrogen charging and diffusivity analysis
- Quasi-static tensile testing with varying stress triaxialities
- Fractography analysis of fracture surfaces under hydrogen and air conditions
Key Findings
- Hydrogen content and diffusivity vary between base metals and weld regions
- Fracture modes include dimples, delaminations, fisheyes, quasi-cleavage, and weld flaws
- Welds showed distinct features like pineapple slices and faceted regions
- Inclusions and hard bands strongly influence crack initiation and propagation
Conclusions
The study provides valuable insights into hydrogen embrittlement in pipeline steels, highlighting microstructural sensitivity and fracture mechanisms. These findings support the safe repurposing of natural gas pipelines for hydrogen transport.
Acknowledgments
This work was conducted within the Sustainable Materials Science group, Department of Materials, Textiles and Chemical Engineering, Ghent University. The author acknowledges the support of collaborators and technical staff.