The effect of hydrogen on the fracture toughness of friction‐stir welded API 5L X70 pipeline steels

The effect of hydrogen on the fracture toughness of friction‐stir welded API 5L X70 pipeline steels

The hydrogen embrittlement (HE) leads to severe steel degradation of mechanical properties. The hydrogen atoms diffuse into the steel and get positioned into reversible and irreversible trap sites. The pipe to transport oil and gas needs to be welded to construct long‐distance pipeline projects; thu...

Full description

Saved in:
Bibliographic Details
Published in:Fatigue & fracture of engineering materials & structures Vol. 45; no. 10; pp. 3009 - 3024
Main Authors: Giarola, Joseane M., Avila, Julian A., Cintho, Osvaldo M., Pinto, Haroldo C., Oliveira, Marcelo F., Bose Filho, Waldek W.
Format: Journal Article
Language:English
Published: Oxford Wiley Subscription Services, Inc 01-10-2022
Subjects:
API 5L X70
Base metal
Ductile fracture
Ductile-brittle transition
Fracture mechanics
Fracture toughness
Friction
Friction stir welding
Gas pipelines
Heat treating
High strength low alloy steels
Hydrogen
Hydrogen atoms
Hydrogen charging
Hydrogen embrittlement
Mechanical properties
Microstructure
Steel
Structural steels
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The hydrogen embrittlement (HE) leads to severe steel degradation of mechanical properties. The hydrogen atoms diffuse into the steel and get positioned into reversible and irreversible trap sites. The pipe to transport oil and gas needs to be welded to construct long‐distance pipeline projects; thus, friction‐stir welding (FSW) has proven an excellent alternative to joining these pipelines. Therefore, this work assessed and analyzed the influence of hydrogen on the microstructure and fracture toughness of API 5L X70 steel welded by friction‐stir welding. The in‐service conditions were simulated by charging the specimen electrolytically in a 3.5% NaCl water solution with an intensity current of 2 mA·cm−2. According to fracture toughness tests, the base metal (BM) was more affected by hydrogen embrittlement than the friction‐stir zone (SZ), with a fracture toughness reduction of 20% after hydrogen charging. The SZ fracture toughness did not statistically show changes in hydrogen charging by the used times; however, the fracture mechanism changed from ductile to brittle‐like after 4 days of charging. The SZ depicted a better fracture toughness than BM due to the bainitic microstructure, a significant amount of irreversible hydrogen trapping. Highlights The influence of hydrogen embrittlement on the FSW welded steel joints was studied. Fracture toughness on hydrogen embrittlement is affected by FSW microstructure. The hydrogen charging reduces the ductility in the FSW steel joints. The embrittlement affected the base metal more than the stir zone.
Bibliography:Funding information
National Council for Scientific and Technological Development, Grant/Award Number: 165065/2017‐6
Joseane Giarola would like to acknowledge the National Council for Scientific and Technological Development, CNPq, “Scholarship ‐ Brazil.” Process: 165065/2017‐6.
ISSN:8756-758X
1460-2695
DOI:10.1111/ffe.13799