Hydrogen Trapping In Metals Research Articles

Hydrogen trapping in alloys studied by thermal desorption spectrometry

Thermal desorption spectrometry (TDS) is a powerful experimental technique used to characterize hydrogen trapping in metals. The passage of hydrogen through a metal is hindered by lattice imperfections, which tend to attract and bind it. The susceptibility of materials to hydrogen embrittlement is directly related to the interaction between traps (defects) and hydrogen. Since trapping affects the metal's diffusivity, it has a major influence on the hydrogen assisted cracking (HAC) phenomenon. Hydrogen trapping is usually evaluated on the basis of reaction controlled mechanisms. Our studies are based on the measurements of temperatures of the gas desorption, the heating rate, and the activating energy. This paper reviews TDS′ applications in quantitative studies of hydrogen trapping and release behavior in crystalline metals. We will discuss both the mechanisms proposed for hydrogen embrittlement in hydride and non-hydride systems and the differences between hydrogen effects on light and heavy metals alloys. In this paper, we compared between duplex Ti–6Al–4V, magnesium (Mg) alloys, and duplex stainless steels (DSS) which can create hydrides in certain conditions. We discuss hydrogen-induced second phases formation, hydrogen's physical trapping, and how these processes affect hydrogen embrittlement in those alloys. In this research, we give another aspect to the trapping mechanism exposed to different hydrogen charging environments by low and high hydrogen fugacity. The main factors controlling the embrittlement phenomenon are the irreversible activation trapping energy, hydrogen fugacity, and second phases' contents. The trapping mechanisms in duplex Ti–6Al–4V, Mg, and DSS and the prediction of failure will be discussed in detail.

Adaptation of the electrochemical permeation technique for studying entry, transport and trapping of hydrogen in metals

The electrochemical permeation and desorption techniques for studying the entry, transport and trapping of hydrogen in metals are outlined. These techniques are susceptible to numerous pitfalls. To obtain reliable data, the experimental conditions must be carefully controlled. As an example, the permeation of hydrogen through and the desorption of hydrogen from cathodically charged Armco iron membranes were investigated. The analysis of the partial permeation transients and then the analysis of the desorption rate of hydrogen from both sides of the membrane enabled determination the lattice diffusivity of hydrogen as well as the amounts and distribution of the diffusible and trapped hydrogen.

Reversible and irreversible hydrogen trapping in metals: new computer-based code THYDA

Use of metallic materials for fusion reactor components and their performance in the presence of hydrogen isotopes require a development of a physical transport model that permits to explain the dynamics of hydrogen absorption and release. Trapping and release processes will strongly affect hydrogen isotopes inventories. The non-linear nature of hydrogen diffusion equations requires a numerical analysis. In this work a new computer code named THYDA was developed. In relation to thermal cycles, THYDA permits to calculate the concentrations of trapped and movable hydrogen atoms in metallic samples as well as hydrogen evolution rates during thermal desorption at elevated temperature with variable heating rates. In these calculations it is possible to take into account both the internal and external sources of hydrogen isotopes (i.e. generation in (n, p) nuclear reactions and by D-T ion implantation).

Modeling of hydrogen diffusion in metals

The study of the diffusion of hydrogen in metals is very important to further understand the hydrogen embrittlement of metals. To describe the diffusion of hydrogen in metals the diffusion equation deduced from Fick's law under an ideal condition has been generally used and the effect of hydrogen trapping in metals has been neglected. In the process of hydrogen diffusion through a metal, hydrogen fills the traps continuously and the fraction of the traps filled by hydrogen, which have only little effect on the diffusion of hydrogen, may be different at different places because the distribution of hydrogen concentration may be different at different places. Thus the hydrogen diffusion coefficient in the metal may also be different at different positions, i.e., the diffusion coefficient should be affected by time in a dynamic process of hydrogen diffusion through a metal. But in the previous analyses, the above fact is not considered and the hydrogen diffusion coefficient is generally taken as a constant. In the present paper a new model of hydrogen diffusion in metals in which the effect of time is taken into account is developed.

An improved model for hydrogen trapping in metals

An improved model for hydrogen trapping in metals

Profile studies of hydrogen trapping in metals due to ion damage

The retention of hydrogen isotopes in Mo at room temperature after ion implantation damage has been studied by measurements of H depth profiles and total D retained in the near-surface region. Implantations of He, O, Ne, and Bi in a fluence range 3×1014–2×1017/cm2 were followed by 8-keV hydrogen bombardment to fluences of 2×1015–2×1017/cm2. Large enhancements in the amount of hydrogen retained in preimplanted samples over samples without prior implantation have been observed and are interpreted in terms of damage trapping. For a given predamage ion fluence hydrogen retention increases linearly with hydrogen fluence until a saturation level is reached. Increased predamage fluence results in increased saturation level for hydrogen trapping, with average concentrations as high as ∼10 at.% achieved. An ion-mass dependence indicates that the lighter ions, which create fewer primary displacements, are more effective in hydrogen trapping, suggesting a dependence on the damage density in the ion cascades.