Determining the effective hydrogen diffusion coefficient in 100Cr6

In general, hydrogen permeabilityΦ of the alloy membrane is expressed as the product of the hydrogen diffusion coefficient D and the hydrogen solution coefficient K. Therefore, to improve the hydrogen permeability efficiently, the values of K and D should be separately considered. In the present study, hydrogen absorption and permeation behaviors of the Nb19Ti40Ni41 alloy consisting of the eutectic phase are investigated by measuring pressure-composition-isotherm (PCI) and by the hydrogen flow method and compared with those of palladium. The hydrogen absorption in the Nb19Ti40Ni41 alloy does not obey the Sieverts’ law in the pressure region of 0-1.0MPa at 523K, but it shows linear relationship between the difference in the square root of hydrogen pressure and hydrogen content between 0.1 and 0.4MPa. Although the value of D for the Nb19Ti40Ni41 alloy is considerably lower than that of palladium, its high K value enhances the hydrogen permeability Φ. It is suggested that the enhancement of D by microstructural control for Nb19Ti40Ni41 alloy is effective for improvement of Φ.

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Investigation of hydrogen diffusion behavior in 12Cr2Mo1R(H) steel by electrochemical tests and first-principles calculation

Anti-Corrosion Methods and Materials ◽

10.1108/acmm-01-2021-2429 ◽

2021 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Xiang Qiu ◽

Kun Zhang ◽

Qin Kang ◽

Yicheng Fan ◽

Hongyu San ◽

...

Keyword(s):

Activation Energy ◽

Diffusion Coefficient ◽

Hydrogen Atom ◽

Hydrogen Embrittlement ◽

First Principles ◽

Hydrogen Diffusion ◽

First Principles Calculations ◽

Content Type ◽

Diffusion Behavior ◽

Hydrogen Diffusion Coefficient

Purpose This paper aims to study the mechanism of hydrogen embrittlement in 12Cr2Mo1R(H) steel, which will help to provide valuable information for the subsequent hydrogen embrittlement research of this kind of steel, so as to optimize the processing technology and take more appropriate measures to prevent hydrogen damage. Design/methodology/approach The hydrogen diffusion coefficient of 12Cr2Mo1R(H) steel was measured by the hydrogen permeation technique of double electrolytic cells. Moreover, the influence of hydrogen traps in the material and experimental temperature on hydrogen diffusion behavior was discussed. The first-principles calculations based on density functional theory were used to study the occupancy of H atoms in the bcc-Fe cell, the diffusion path and the interaction with vacancy defects. Findings The results revealed that the logarithm of the hydrogen diffusion coefficient of the material has a linear relationship with the reciprocal of temperature and the activation energy of hydrogen atom diffusion in 12Cr2Mo1R(H) steel is 23.47 kJ/mol. H atoms stably exist in the nearly octahedral interstices in the crystal cell with vacancies. In addition, the solution of Cr/Mo alloy atom does not change the lowest energy path of H atom, but increases the diffusion activation energy of hydrogen atom, thus hindering the diffusion of hydrogen atom. Cr/Mo and vacancy have a synergistic effect on inhibiting the diffusion of H atoms in α-Fe. Originality/value This article combines experiments with first-principles calculations to explore the diffusion behavior of hydrogen in 12Cr2Mo1R(H) steel from the macroscopic and microscopic perspectives, which will help to establish a calculation model with complex defects in the future.

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Influence of Phases Stability on the Hydrogen Diffusion Coefficient in Ti-6Al-4V

Materials Science Forum ◽

10.4028/www.scientific.net/msf.986.33 ◽

2020 ◽

Vol 986 ◽

pp. 33-40

Author(s):

Mohammed Kasim Mohsun

Keyword(s):

Heat Treatment ◽

Diffusion Coefficient ◽

Titanium Alloys ◽

Hydrogen Diffusion ◽

Volume Fraction ◽

Substantial Effect ◽

Diffusion Annealing ◽

Hydrogen Treatment ◽

Β Phase ◽

Hydrogen Diffusion Coefficient

For a unique microstructure creation, thermo-hydrogen treatment (THT), using hydrogen as a temporary alloying element within the heat treatment, is applied. This advanced heat treatment requires reliable data about the hydrogen diffusion coefficient (DH) for understanding diffusion kinetics and its effect on the mechanical behavior of the resulted phases. In this research, three different homogeneous microstructures were established for the investigation using different homogenization parameters. After that, the concentration of hydrogen, charged in the half-length of thin titanium rods via electrochemical hydrogenation, is specified. Then, a diffusion annealing heat treatment was carried out at different temperatures, leading to hydrogen diffusion in the hydrogenated specimens. Furthermore, DH was systematically determined using two methods including the explicit finite difference method (EFDM) and Matano technique (MT). For this purpose, Abaqus software was employed for modeling the hydrogen gradient established in the specimens. Additionally, scanning electron microscopy (SEM) was used for the microstructure examination in order to specify the influence of different hydrogen concentrations on the hydrogenated specimens. The experimental outcomes reveal a substantial effect of the β phase stability and grains sizes of the β and α phases on the hydrogen diffusion. Correspondingly, the results confirm that DH was independent of the hydrogen concentration, and obeys an Arrhenius-type temperature dependence. Furthermore, hydrogen diffusion in the α+β titanium alloys Ti-6Al-4V was slower in comparison to the hydrogen diffusion in the metastable β titanium alloys Ti-10V-2Fe-3Al. In conclusion, it was observed that DH is influenced by the previously performed heat treatments that determine the resulted microstructure types, and a slight influence of the volume fraction of the α phase on DH was observed as well.

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Influence of Experimental Conditions and Calculation Method on Hydrogen Diffusion Coefficient Evaluation at Elevated Temperatures

International Hydrogen Conference (IHC 2016): Materials Performance in Hydrogen Environments ◽

10.1115/1.861387_ch56 ◽

2017 ◽

pp. 495-503 ◽

Cited By ~ 2

Keyword(s):

Diffusion Coefficient ◽

Calculation Method ◽

Elevated Temperatures ◽

Hydrogen Diffusion ◽

Experimental Conditions ◽

Hydrogen Diffusion Coefficient

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Hydrogen Diffusion Coefficient during Hydrogen Permeation through Nb-Based Hydrogen Permeable Membranes

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.283-286.225 ◽

2009 ◽

Vol 283-286 ◽

pp. 225-230 ◽

Cited By ~ 2

Author(s):

Hiroshi Yukawa ◽

G.X. Zhang ◽

N. Watanabe ◽

Masahiko Morinaga ◽

T. Nambu ◽

...

Keyword(s):

Crystal Structure ◽

Diffusion Coefficient ◽

High Temperature ◽

Solid Solutions ◽

Diffusion Coefficients ◽

Hydrogen Diffusion ◽

Hydrogen Permeation ◽

Pure Niobium ◽

Hydrogen Diffusion Coefficient

The hydrogen diffusion coefficients are investigated during the hydrogen permeation through Nb-based hydrogen permeable membranes at high temperature. It is found that the hydrogen diffusion coefficient for pure niobium under practical conditions is much lower than the reported values measured for dilute hydrogen solid solutions. Surprisingly, the hydrogen diffusion is found to be faster in Pd-Ag alloy with fcc crystal structure than in pure niobium with bcc crystal structure at 773K during the hydrogen permeation. It is also found that the addition of Ru or W into niobium increases the hydrogen diffusion coefficient under the practical conditions.

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