The characteristics of hydrogen diffusion and concentration around a crack tip concerned with hydrogen embrittlement

2002 ◽  
Vol 44 (3) ◽  
pp. 407-424 ◽  
Author(s):  
A.Toshimitsu Yokobori ◽  
Yasrou Chinda ◽  
Takenao Nemoto ◽  
Koji Satoh ◽  
Tetsuya Yamada
Keyword(s):  
Hydrogen Embrittlement ◽  
Hydrogen Diffusion ◽  
Crack Tip

Calculation of Fracture Toughness for Hydrogen Embrittlement in a Pressure Vessel

2009 ◽  
Vol 294 ◽  
pp. 49-63
Author(s):  
Ehsan Mahdavi ◽  
Mahmoud Mosavi Mashhadi
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Hydrogen Embrittlement ◽  
Intensity Factor ◽  
Pressure Vessel ◽  
Hydrogen Diffusion ◽  
Crack Tip ◽  
Mass Diffusion ◽  
Coupled Stress

An analytical procedure is developed to design and predict the behavior of a pressure vessel. If a pressure vessel contains hydrogen, it is difficult to predict what will happen in the future. In this study, this is accounted for and the stress intensity factor for mode-Ι is calculated because the main factor controlling mass diffusion, as a driving force, is related to the stress in this mode. Also, it is known that the stress intensity factor depends upon concentration. The main challenge in hydrogen embrittlement is the prediction of crack growth and the estimation of lifetime for a pressure vessel. This paper investigates the effect of hydrogen diffusion upon crack in a pressure vessel by using numerical finite-element simulations. The fracture behavior of the alloy as related to hydrogen embrittlement was also studied. The computational simulations involved sequentially-coupled stress and mass-diffusion concentrations at the crack tip. Although there have been various previous works in this area, most of them have been experimental estimates of hydrogen diffusion. In this paper, we calculate the stress intensity factor by using the finite-element method (FEM) and use mathematical analysis simultaneously. The analytical method alone could not be used because the mass diffusion has special characteristics. That is, the treatment of diffusion is different at each step. We conducted finite-element modeling simulations of the intergranular fracture of alloy X-750 due to hydrogen embrittlement. Sequentially coupled stress and mass diffusion determinations were carried out in order to determine crack tip stresses and hydrogen diffusivity in the crack-tip region. Good qualitative agreement between the FEM modeling and the analysis was observed.

Microstructure Imaging, Precipitation Formation and Mechanical Properties: Al–Li and Al–Mg–Zn Alloys

2019 ◽  
Author(s):  
Wilfried Wunderlich ◽  
Janos Lendvai ◽  
Hans-Joachim Gudladt
Keyword(s):  
Hydrogen Embrittlement ◽  
Driving Force ◽  
Hydrogen Diffusion ◽  
Nano Particles ◽  
Peak Hardness ◽  
Free Zone ◽  
The Third ◽  
Transmission Electron ◽  
Moisture Conditions ◽  
Precipitation Formation

This article describes concepts of three features of microstructure–properties relationship, first the imaging and formation of nano-particles, then their contribution to hardness, and finally hydrogen embrittlement during fatigue. First, we briefly review the imaging modes in transmission electron microscopy (TEM) for nano-sized precipitates. The next issue is the hardening in Aluminum alloys, which is caused by GP-zones or precipitates, formed at the second step of the annealing process. After homogenization, the peak-hardness can be generally achieved by a few hours of annealing between 120°C and 200°C. Hardness measurements and equal-channel axial pressing (ECAP) showed that even at room temperature the driving force for formation of the particles is so strong that already within one hour of annealing after homogenization a remarkable hardening occurs. The third issue, hydrogen embrittlement, is caused by oxidation of pure Al surfaces produced at the crack tip during fatigue under ambient or wet moisture conditions. The cracks propagate preferentially along the precipitation free zone adjacent to grain boundaries, where hydrogen diffusion is fastest.

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

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.

scholarly journals Transient Hydrogen Diffusion-Elastoplastic Coupling Analysis near a Blunting Crack Tip

2008 ◽  
Vol 74 (737) ◽  
pp. 28-36 ◽  
Author(s):  
Hirokazu KOTAKE ◽  
Ryosuke MATSUMOTO ◽  
Shinya TAKETOMI ◽  
Noriyuki MIYAZAKI
Keyword(s):  
Hydrogen Diffusion ◽  
Crack Tip ◽  
Coupling Analysis

Role of Residual Stresses and Strains Fields Generated by Heat Treatments on the Hydrogen Embrittlement of a Nuclear Reactor Pressure Vessel

2011 ◽  
Author(s):  
J. Toribio ◽  
D. Vergara ◽  
M. Lorenzo ◽  
J. J. Marti´n
Keyword(s):  
Hydrogen Embrittlement ◽  
Pressure Vessel ◽  
Nuclear Reactor ◽  
Hydrogen Diffusion ◽  
Operation Time ◽  
Heat Treatments ◽  
Reactor Pressure Vessel ◽  
Low Carbon ◽  
Tempering Temperature ◽  
Reactor Pressure

The wall of a nuclear reactor pressure vessel can undergo a reduction of its mechanical properties due to the presence of hydrogen, a process known as hydrogen embrittlement (HE). A numerical model of hydrogen diffusion assisted by stress and strain was used in this paper to evaluate the HE process in the wall of a real nuclear reactor pressure vessel, formed by a bimaterial (stainless steel and low carbon steel). In this sense, a quantitative analysis was carried out of the influence of tempering heat treatments conditions applied to these two steels on hydrogen concentration accumulated in the nuclear reactor vessel during its operation time. To this end, the most relevant parameters of these heat treatments were considered: (i) tempering temperature and (ii) tempering time.

Hydrogen inhibited phase transition near crack tip – An atomistic mechanism of hydrogen embrittlement

2019 ◽  
Vol 44 (31) ◽  
pp. 17146-17153 ◽  
Author(s):  
Xiao Xing ◽  
Hao Zhang ◽  
Gan Cui ◽  
Jianguo Liu ◽  
Zili Li
Keyword(s):  
Phase Transition ◽  
Hydrogen Embrittlement ◽  
Crack Tip

2713 Unsteady hydrogen diffusion analysis around the crack tip on cyclic loading

2007 ◽  
Vol 2007.20 (0) ◽  
pp. 615-616
Author(s):  
Hirokazu KOTAKE ◽  
Ryosuke MATSUMOTO ◽  
Shinya TAKETOMI ◽  
Noriyuki MIYAZAKI
Keyword(s):  
Cyclic Loading ◽  
Hydrogen Diffusion ◽  
Crack Tip ◽  
Diffusion Analysis
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