Zirconium alloys are common fuel claddings in nuclear fission reactors and are susceptible to the effects of hydrogen embrittlement. There is a need to be able to detect and image hydrogen at the atomic scale to gain the experimental evidence necessary to fully understand hydrogen embrittlement. Through the use of deuterium tracers, atom probe tomography (APT) is able to detect and spatially locate hydrogen at the atomic scale. Previous works have highlighted issues with quantifying deuterium concentrations using APT due to complex peak overlaps in the mass-to-charge-state ratio spectrum between molecular hydrogen and deuterium (H2 and D). In this work, we use new methods to analyze historic and simulated atom probe data, by applying currently available data analysis tools, to optimize solving peak overlaps to improve the quantification of deuterium. This method has been applied to literature data to quantify the deuterium concentrations in a concentration line profile across an α-Zr/deuteride interface.

A model has been developed which simulates the deformation of single crystal austenitic stainless steels and captures the effects of hydrogen on stress corrosion cracking. The model is based on the crystal plasticity theory which relates critical resolved shear stress to plastic strain and the strength of the crystal. We propose an analytical representation of hydrogen interactions with the material microstructure during deformation and simulate the effects hydrogen will have on void growth prior to fracture. Changes in the mechanical properties of the crystal prior to fracture are governed by the interaction of hydrogen atoms and ensembles of dislocations as the crystal plastically deforms and is based on the hydrogen enhanced localised plasticity (HELP) mechanism. The effects of hydrogen on void growth are considered by analysing the effect of hydrogen on the mechanical property of material bounding an embedded void. The model presented has been implemented numerically using the User Material (UMAT) subroutine in the finite element software (ABAQUS) and has been validated by comparing simulated results with experimental data. Influencing parameters have been varied to understand their effect and test sensitivities.

To understand the effect of pH value on the corrosion and corrosion fatigue behavior of AM60 magnesium alloy, electrochemical tests, viz., electrochemical impedance spectroscopy (EIS) and fatigue tests, were carried out in PBS (phosphate buffered saline) solutions of pH 5.2, 7.4, and 9.0. The microstructure was investigated by scanning electron microscopy (SEM). Results are as follows: (i) the corrosion mechanism of AM60 under different pH values was different according to EIS; (ii) the corrosion resistance and corrosion fatigue life reduced in the following order: pH 9.0 > pH 7.4 > pH 5.2; (iii) the crack initiation was associated with hydrogen embrittlement of AM60 on the basis of fractographic analysis.

The hydrogen embrittlement of 12Cr2Mo1R(H) steel at different strain rates were investigated after hydrogen precharging for 4 h in a 0.5 M H2SO4 solution with 2 g/L ammonium thiocyanate. Results showed that the embrittlement index increased and gradually reached a relative stable value of about 20% at the strain rate of 5 × 10−5 s−1 with the decrease of strain rates. SEM images depicted small and deep flakes at high strain rates, while flakes grew larger at slow strain rates. Most hydrogen-induced cracks (HICs) were transgranular fracture through lath grain of bainitic ferrite. High strain field surrounds the crack tips, which makes the crack tips of two close and parallel cracks deflect toward each another and even form crack coalescence. The electron backscatter diffraction technique was used to investigate the effects of grain boundaries, recrystallization fraction, kernel average misorientation map, texture component, and coincidence site lattice boundaries on the HIC propagation. High densities of dislocations and strain concentrations were found around the cracks, where grains are highly sensitive to HIC.

Hydrogen exposure has been found to result in metal embrittlement. In this work, we use nanoindentation to study the mechanical properties of polycrystalline tungsten subjected to deuterium plasma exposure. For the purpose of comparison, nanoindentation tests on exposed and unexposed reference tungsten were carried out. The results exhibit a decrease in the pop-in load and an increase in hardness on the exposed tungsten sample after deuterium exposure. No significant influence of grain orientation on the pop-in load was observed. After a desorption time of td ≥ 168 h, both the pop-in load and hardness exhibit a recovering trend toward the reference state without deuterium exposure. The decrease of pop-in load is explained using the defactant theory, which suggests that the presence of deuterium facilitates the dislocation nucleation. The increase of hardness is discussed based on two possible mechanisms of the defactant theory and hydrogen pinning of dislocations.

Hydrogen embrittlement behaviors of a 22Mn–0.6C (mass%) twinning induced plasticity (TWIP) steel with the grain sizes of 21 μm (coarse grain) and 0.58 μm (ultrafine grain) were investigated by means of hydrogen precharging and subsequent slow strain rate tensile tests. The total elongation and fracture stress for both of the coarse-grained and ultrafine-grained specimens decreased by hydrogen charging. The area fraction of the brittle fracture surfaces in the ultrafine-grained specimen was much smaller than that in the coarse-grained specimen. Three-point bending test also showed that the reduction of the fracture toughness by the introduction of hydrogen was much smaller in the ultrafine-grained specimen than that in the coarse-grained specimen. It was concluded that the suppressed hydrogen embrittlement by grain refinement in the 22Mn–0.6C TWIP steel was probably due to the smaller hydrogen contents per unit grain boundary area in the finer grain-sized material.

To clarify the effect of bainite in microstructure on hydrogen diffusion and trapping behavior and susceptibility to hydrogen assisted cracking of API grade linepipe steel, three specimens with different fraction of bainite in the microstructure are used. Firstly, hydrogen diffusion and trapping behaviors of the steels are studied by utilizing the electrochemical permeation technique. For fundamental analysis on the experimental data, a variety of diffusion parameters were determined by curve-fitting with a theoretical diffusion equation based on numerical finite difference method (FDM). It indicates that the steel with higher fraction of bainite exhibits much higher sub-surface hydrogen concentration and much lower apparent hydrogen diffusivity. This behavior can be understood by the fact that the steel containing higher fraction of bainite in the microstructure has higher concentration of reversible traps and consequent larger diffusible hydrogen, leading to much slower diffusion kinetics of hydrogen atoms. Consequently, the susceptibility to hydrogen induced cracking (HIC) and sulfide stress cracking (SSC) of the steel with higher fraction of bainite increases significantly.

In this work, direct potential measurements during cold rolling of zinc and X20Cr13stainless steel were carried out in the rolling slit to follow the tribologic and galvanicmechanisms of hydrogen formation and absorption on the surface of the working rolls madeof DHQ1 grade steel. An Ag/AgCl in 3.5 M KCl reference microelectrode was used to recordthe open circuit potential of the electrochemical system roller-product immersed intocommercially relevant electrolyte (rolling emulsion) with a pH value of 4.5 and anelectric conductivity 46 mS cm-1. The potential shift into either negative or positivedirection of the rolls-product system gives information on the processes taking place atthe surface in the course of the friction. A detailed discussion of the in-situpotentiometry experiments reveals a stationary situation established between thedestruction and repassivation of the surface structures during continuous cold rollingaccompanied with intensive hydrogen evolution. Galvanic coupling of the working rolls withthe product significantly intensifies the hydrogen embrittlement related problems of therolls. Atomic hydrogen is adsorbed on the surface and exhibits a pressure supportedabsorption into the rolls during their whole lifetime.

Depuis plus de 30 ans, le Commissariat à l'Énergie Atomique (CEA) a mis au point et systématiquement utilisé l'essai de disques pour étudier et mesurer la sensibilité à l'hydrogène gazeux des matériaux. En 1990, cette technique expérimentale est devenue une norme AFNOR pour sélectionner les alliages métalliques destinés à réaliser des bouteilles et réservoirs d'hydrogène sous haute pression. L'essai de disques compare la résistance à la pression de membranes essayées sous hélium et sous hydrogène dans les mêmes conditions expérimentales. La technique est simple, sensible et ses résultats sont fiables ; l'essai de disques permet des études originales et variées ; il révèle des paramètres qui ne sont pas toujours significatifs avec des méthodes d'essais moins performantes. Tout d'abord, nous présentons une synthèse de différents résultats généraux : la fragilisation par l'hydrogène en fonction de la résistance mécanique du matériau, de sa composition chimique et de ses traitements mécaniques et thermiques, l'influence du milieu gazeux (teneur en hydrogène ou en impuretés)... Ensuite, nous montrons plusieurs cas d'endommagement de matériaux : la fragilisation métallurgique consécutive à l'utilisation à température élevée ou moyenne de différents alliages, l'influence d'un vieillissement thermique sur la fragilisation par l'hydrogène gazeux, les différentes fragilisations si l'hydrogène est introduit dans le matériau avant ou pendant l'utilisation de l'équipement, l'influence du mécanisme de durcissement sur le vieillissement thermique et la fragilisation par l'hydrogène, la réduction de la durée de vie en fatigue consécutive au vieillissement thermique en service, au contact avec de l'hydrogène gazeux et à l'importante synergie entre ces deux phénomènes. Les résultats de fragilisation par la température et par l'hydrogène sont analysés de façon à être extrapolés aux conditions extrêmes de sollicitation d'un moteur de fusée : utilisation à haute température sous faible pression partielle d'hydrogène, refroidissement rapide, sursaturation en hydrogène et déformations oligocycliques d'origine thermique.

This review outlines the prospects for gaseous hydrogen, stored in high-pressure cylinders, as a fuel for automotive applications. Following an initial description of hydrogen embrittlement problems encountered in the past in steel cylinders, the article explores the use of other types of gas cylinders, including the recent examples of hoop-wound and fully wound composites. Central to the article is the concept of the volume of hydrogen transported for the minimum amount of container weight. Finally, the role of international standards in developing safe and efficient cylinders for this application is emphasized.