Hydrogen embrittlement processes in microalloyed steel notched tensile samples

• Published in: Theoretical and applied fracture mechanics 2021-04, Vol.112, p.102878, Article 102878
• Main Authors: Cayón, A., Gutiérrez-Solana, F., Arroyo, B., Álvarez, J.A.
• Format: Article
• Language: English
• Subjects: Axial stress; Correlation analysis; Displacement rate; FAD diagram; Finite element method; Fracture mechanics; Fracture toughness; Gas pipelines; High strength low alloy steels; Hydrogen; Hydrogen charging; Hydrogen embrittlement; Hydrostatic stress; Loading rate; Mechanical properties; Microalloying; Natural gas; Notched samples; Petroleum pipelines; Plastic deformation; Strain
• ISSN: 0167-8442; 1872-7638
• DOI: 10.1016/j.tafmec.2020.102878

•Two microayolled steels have been studied under HE conditions after cathodic charged.•Two different types of axisymmetric round notched tensile specimens have been tested under continuous hydrogen aforementiones environments.•The correlation between the observed fracture micromechanisms with local environmental and mechanical conditions have been analysed.•Analysis based on the hydrostatic stress and strain distribution in the different geometries explains the results.•A validation based on FAD diagrams was carried out. In this work, two microalloyed steels, one used for oil&gas pipelines and the other one for structural components in hydrotreating reactors in petrochemical industries, have been studied under hydrogen embrittlement (HE) conditions. They have been cathodically charged with hydrogen under different aggressive conditions, its hydrogen content being determined afterwards. In order to know the effect of triaxiality on the HE behaviour of this steel, two different types of axisymmetric round notched tensile specimens have been tested under continuous hydrogen charging processes, whilst varying cathodic charging conditions and loading rate. The effects on the global mechanical characterization have been analysed, as well as the correlation between the observed fracture micromechanisms with both local environmental (as hydrogen concentration) and mechanical conditions (as hydrostatic stress and plastic strain determined with a finite elements analysis). Also, subcritical cracking due to embrittlement has been analysed and compared with those obtained by fracture mechanics standardised specimens.