Hydrogen effect on fracture toughness of pipeline steel welds, with in situ hydrogen charging

Steel welds representing three generations of pipeline steel were studied against hydrogen effect, using the fracture toughness parameter J integral which is a measure of the plastic work. The influence of hydrogen on the growth of a partial wall defect is studied and comparisons with the growth of the same defect in air are presented. The tests conducted were three-point bending fracture toughness tests, in air and in a hydrogen environment simulated by electrolysis. Reduction in J0 was observed in all pipeline steel grades as the current density increases, which was more pronounced in the base metal rather than in the heat affected zone. The different microstructures of the welded steels are observed and correlated to the reduction in plasticity. It is concluded that microstructure seems to be the decisive parameter for the selection of a pipeline steel for service in a hydrogen environment.

Download Full-text

Probing hydrogen effect on nanomechanical properties of X65 pipeline steel using in-situ electrochemical nanoindentation

Materials Science and Engineering A ◽

10.1016/j.msea.2021.141819 ◽

2021 ◽

pp. 141819

Author(s):

Dong Wang ◽

Anette Brocks Hagen ◽

Di Wan ◽

Xu Lu ◽

Roy Johnsen

Keyword(s):

Pipeline Steel ◽

Hydrogen Effect ◽

Nanomechanical Properties

Download Full-text

Standardization of CTOD Toughness Correction for Constraint Loss in Steel Components

Volume 1: Codes and Standards ◽

10.1115/pvp2008-61076 ◽

2008 ◽

Author(s):

Fumiyoshi Minami ◽

Mitsuru Ohata

Keyword(s):

Fracture Toughness ◽

Fracture Criterion ◽

Shape Parameter ◽

Pipeline Steel ◽

Fracture Initiation ◽

Failure Assessment ◽

Fracture Assessment ◽

Steel Welds ◽

Weibull Stress ◽

Fracture Toughness Specimen

A standardized procedure for correction of CTOD fracture toughness for constraint loss in steel components is presented. The equivalent CTOD ratio β = δ/δWP is developed on the basis of the Weibull stress fracture criterion, where δ and δWP are CTODs of the standard fracture toughness specimen and the wide plate component, respectively, at the same level of the Weibull stress. With the CTOD ratio β, the critical CTOD δWP, cr of the wide plate that is equivalent to δcr at brittle fracture initiation is given as δWP, cr = δcr/β. Nomographs of β are provided as a function of the crack type and size in the component, the yield-to-tensile ratio of the material and the Weibull shape parameter m. The fracture assessment with β is shown within the context of a failure assessment diagram (FAD), which includes the pipeline steel welds with a notch in the weld metal.

Download Full-text

In situ electrochemical nanoindentation of FeAl (100) single crystal: Hydrogen effect on dislocation nucleation

Journal of Materials Research ◽

10.1557/jmr.2009.0084 ◽

2009 ◽

Vol 24 (3) ◽

pp. 1105-1113 ◽

Cited By ~ 25

Author(s):

Afrooz Barnoush ◽

Christian Bies ◽

Horst Vehoff

Keyword(s):

Single Crystal ◽

Surface Orientation ◽

Dislocation Nucleation ◽

Electrochemical Potential ◽

Displacement Curve ◽

Hydrogen Effect ◽

Hydrogen Atoms ◽

Elastic Plastic ◽

Hydrogen Charging

The hydrogen effect on dislocation nucleation in FeAl single crystal with (100) surface orientation has been examined with the aid of a specifically designed nanoindentation setup for in situ electrochemical experiments. The effect of the electrochemical potential on the indent load–displacement curve, especially the unstable elastic-plastic transition (pop-in), was studied in detail. The observations showed a reduction in the pop-in load for both samples due to in situ hydrogen charging, which is reproducibly observed within sequential hydrogen charging and discharging. Clear evidence is provided that hydrogen atoms facilitate homogeneous dislocation nucleation.

Download Full-text

Investigation of Hydrogen Embrittlement Susceptibility and Fracture Toughness Drop after in situ Hydrogen Cathodic Charging for an X65 Pipeline Steel

Micromachines ◽

10.3390/mi11040430 ◽

2020 ◽

Vol 11 (4) ◽

pp. 430 ◽

Cited By ~ 2

Author(s):

Helen Kyriakopoulou ◽

Panagiotis Karmiris-Obratański ◽

Athanasios Tazedakis ◽

Nikoalos Daniolos ◽

Efthymios Dourdounis ◽

...

Keyword(s):

Fracture Toughness ◽

Volume Fraction ◽

Pipeline Steel ◽

High Strength ◽

Electrolytic Cell ◽

Low Alloy Steels ◽

Crack Tip Opening Displacement ◽

Opening Displacement ◽

Alloy Steels

The present research focuses on the investigation of an in situ hydrogen charging effect during Crack Tip Opening Displacement testing (CTOD) on the fracture toughness properties of X65 pipeline steel. This grade of steel belongs to the broader category of High Strength Low Alloy Steels (HSLA), and its microstructure consists of equiaxed ferritic and bainitic grains with a low volume fraction of degenerated pearlite islands. The studied X65 steel specimens were extracted from pipes with 19.15 mm wall thickness. The fracture toughness parameters were determined after imposing the fatigue pre-cracked specimens on air, on a specific electrolytic cell under a slow strain rate bending loading (according to ASTM G147-98, BS7448, and ISO12135 standards). Concerning the results of this study, in the first phase the hydrogen cations’ penetration depth, the diffusion coefficient of molecular and atomic hydrogen, and the surficial density of blisters were determined. Next, the characteristic parameters related to fracture toughness (such as J, KQ, CTODel, CTODpl) were calculated by the aid of the Force-Crack Mouth Open Displacement curves and the relevant analytical equations.

Download Full-text