Mechanism of Hydrogen Embrittlement of Austenitic Steels

2007 ◽  
Vol 539-543 ◽  
pp. 4249-4254 ◽  
Author(s):  
V. Shivanyuk ◽  
Valentin G. Gavriljuk ◽  
Jacques Foct
Keyword(s):  
Hydrogen Embrittlement ◽  
Line Tension ◽  
Austenitic Steels ◽  
Hydrogen Atoms ◽  
Conduction Electrons ◽  
Metallic Character ◽  
Spin Resonance ◽  
Localization Of Plastic Deformation ◽  
Dislocation Sources ◽  
Strain Dependent

Three main hypotheses of hydrogen embrittlement (HE) of austenitic steels are discussed based on the studies of the interatomic interactions, hydrogen-induced phase transformations and dislocations properties. Measurements of electron spin resonance and ab initio calculations of the electron structure witness that the concentration of conduction electrons increases due to hydrogen, which enhances the metallic character of interatomic bonds. The hypothesis of brittle hydrogen-induced phases is disproved by the studies of the silicon-alloyed steels: the silicon-caused increase in the fraction of the εH martensite is accompanied by the decrease of HE. Studies of strain-dependent internal friction have shown the hydrogen-caused decrease in the start stress of microplasticity and increase in the velocity of dislocations in accordance with HELP hypothesis. A mechanism of HELP is proposed based on the hydrogencaused enhancement of the metallic character of interatomic bonds, which results in the local decrease of the shear modulus within the hydrogen atmospheres round the dislocations. As consequence, the line tension of the dislocations followed by the hydrogen atoms decreases, which finds its expression in the early start of dislocation sources, decreased distance between dislocations in the pile-ups and increased velocity of dislocations. A mechanism of localization of plastic deformation is proposed based on the observations of the hydrogen-enhanced concentration of equilibrium vacancies.

Hydrogen Brittleness of Austenitic Steels

2010 ◽  
Vol 638-642 ◽  
pp. 104-109 ◽  
Author(s):  
Valentin G. Gavriljuk ◽  
Vladyslav N. Shyvanyuk ◽  
S. M. Teus
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Hydrogen Embrittlement ◽  
Line Tension ◽  
Austenitic Steels ◽  
Alloying Elements ◽  
Hydrogen Brittleness ◽  
Conduction Electrons ◽  
Electronic Concept ◽  
Dislocation Sources

The electronic concept for hydrogen embrittlement (HE) of austenitic steels is developed based on the hydrogen-caused increase of the concentration of free (i.e. conduction) electrons. It is shown that, as consequence, the shear module locally decreases, which in turn leads to the decrease in the stress for activation of dislocation sources, the line tension of dislocations, the distance between the dislocations in pileups and, in consistency with the theory of hydrogen-enhanced localized plasticity (HELP), promotes the reversible hydrogen brittleness. The analysis of the electronic and elasticity approaches to HELP is carried out using the experimental data. The effect of alloying elements on the mechanical properties is studied and a concept for design of hydrogen-resistant austenitic steels is proposed.

A Concept for Development of Hydrogen-Resistant Austenitic Steels

2013 ◽  
Author(s):  
Valentin Gavriljuk ◽  
Bela Shanina ◽  
Vladyslav Shyvanyuk ◽  
Sergey Teus
Keyword(s):  
Solid Solution ◽  
Hydrogen Embrittlement ◽  
Solid Solutions ◽  
Austenitic Steels ◽  
Hydrogen Degradation ◽  
Hydrogen Atoms ◽  
Free Electrons ◽  
Physical Reason ◽  
Hydrogen Resistance

Austenitic steels represent a promising class of engineering materials for hydrogen use in vehicles, e.g. for tanks and pipelines. This topic is analyzed in terms of the effect of alloying elements on the interatomic bonds in the solid solutions and, consequently, on the interaction between hydrogen atoms and dislocations and hydrogen embrittlement, HE. The effect of Cr, Ni, Mn, Mo, Si, Al, Cu, C, N was studied. It is shown that the physical reason for HE amounts to the hydrogen-caused increase in the concentration of free electrons in the austenitic solid solution. For this reason, the alloying with elements decreasing the concentration of free electrons is expected to improve resistance of austenitic steels to HE. Alloying with Cr, Mn, Mo and Si is shown to be useful, whereas Cu, Al, Ni, N assist hydrogen degradation. The role of Ni amounts only to stabilization of the fcc austenitic lattice and its absence or the decrease of its content in steel is desirable. Based on the obtained results, recommendations are made for design of austenitic steels with increased hydrogen resistance.

scholarly journals Hydrogen Embrittlement and Improved Resistance of Al Addition in Twinning-Induced Plasticity Steel: First-Principles Study

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1341
Author(s):  
Lilin Lu ◽  
Jiaqi Ni ◽  
Zhixian Peng ◽  
Haijun Zhang ◽  
Jing Liu
Keyword(s):  
Hydrogen Embrittlement ◽  
Compressive Stress ◽  
First Principles ◽  
Binding Energies ◽  
Austenitic Steels ◽  
Hydrogen Atoms ◽  
Young’S Moduli ◽  
Site Preferences ◽  
Work First ◽  
Interstitial Hydrogen

Understanding the mechanism of hydrogen embrittlement (HE) of austenitic steels and developing an effective strategy to improve resistance to HE are of great concern but challenging. In this work, first-principles studies were performed to investigate the HE mechanism and the improved resistance of Al-containing austenite to HE. Our results demonstrate that interstitial hydrogen atoms have different site preferences in Al-free and Al-containing austenites. The calculated binding energies and diffusion barriers of interstitial hydrogen atoms in Al-containing austenite are remarkably higher than those in Al-free austenite, indicating that the presence of Al is more favorable for reducing hydrogen mobility. In Al-free austenite, interstitial hydrogen atoms caused a remarkable increase in lattice compressive stress and a distinct decrease in bulk, shear, and Young’s moduli. Whereas in Al-containing austenite, the lattice compressive stress and the mechanical deterioration induced by interstitial hydrogen atoms were effectively suppressed.

An electron spin resonance study of the reactions of hydrogen atoms with halocarbons

1986 ◽  
Vol 64 (11) ◽  
pp. 2192-2195 ◽  
Author(s):  
William E. Jones ◽  
Joseph L. Ma
Keyword(s):  
Rate Constants ◽  
Gas Flow ◽  
Esr Spectroscopy ◽  
Flow System ◽  
Electron Spin Resonance Study ◽  
Absolute Rate ◽  
Hydrogen Atoms ◽  
Vinyl Halides ◽  
Spin Resonance ◽  
Spin Resonance Study

The absolute rate constants for the reaction of H atoms with methyl- and vinyl-halides have been determined using esr spectroscopy and a conventional gas flow system. The rate constants determined at 298 ± 2 K at a pressure of 0.55 Torr are methane, (1.7 ± 0.3) × 10−17; ethane, (2.3 ± 0.5) × 10−17; methylfluoride, (4 ± 3) × 10−15; methylchloride, (8 ± 2) × 10−16; methylbromide, (2.1 ± 0.6) × 10−14; vinylfluoride, (1.47 ± 0.02) × 10−13; vinylchloride, (1.66 ± 0.08) × 10−13; and vinylbromide (4.07 ± 0.73) × 10−13 in units of cm3 molecule−1 s−1.

Applications of ESR to Carbonaceous Materials

1982 ◽  
Vol 36 (1) ◽  
pp. 52-57 ◽  
Author(s):  
L. S. Singer ◽  
I. C. Lewis
Keyword(s):  
Free Radicals ◽  
Electron Spin Resonance ◽  
Low Temperature ◽  
Electron Spin ◽  
Paramagnetic Species ◽  
Carbonaceous Materials ◽  
Conduction Electrons ◽  
Spin Resonance ◽  
Higher Temperature ◽  
Low Temperature Pyrolysis

The applications of electron spin resonance (ESR) to carbonaceous materials are reviewed. The stable paramagnetic species observed in the products of low-temperature pyrolysis are odd-alternate neutral free radicals, whereas the unpaired spins of higher temperature carbons and graphites are primarily conduction electrons. The variety of ESR properties and phenomena requires special attention to techniques of measurement and interpretations of results. The relevance to the carbonization process of the free radicals observed by ESR is also discussed.

ESR Of Graphite-Like Amorphous Carbon Thin Film In The 20 – 340 K Temperature Range

2006 ◽  
Vol 984 ◽  
Author(s):  
Gustavo A. Viana ◽  
Francisco C. Marques
Keyword(s):  
Band Gap ◽  
Optical Band Gap ◽  
Ion Beam ◽  
Localized States ◽  
Paramagnetic Centers ◽  
Conduction Electrons ◽  
Temperature Range ◽  
Spin Resonance ◽  
Electron Energy Loss ◽  
Amorphous Carbon Thin Film

AbstractElectron spin resonance of graphite-like a-C thin films is investigated in the 20 K up to 340 K temperature range. The films with sp2 concentration of about 90 % (determined by electron energy loss spectroscopy), with no measurable optical band gap, were prepared by ion beam assisted sputtering. The results revealed an unexpected low density of paramagnetic centers, ascribed to itinerant states (conduction electrons) and not to localized states usually reported for a-C with band gap higher than 1.0 eV.

scholarly journals Hydrogen Embrittlement Behavior of 18Ni 300 Maraging Steel Produced by Selective Laser Melting

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2360 ◽  
Author(s):  
Young Jin Kwon ◽  
Riccardo Casati ◽  
Mauro Coduri ◽  
Maurizio Vedani ◽  
Chong Soo Lee
Keyword(s):  
Hydrogen Embrittlement ◽  
Maraging Steel ◽  
Selective Laser Melting ◽  
Solution Treatment ◽  
Tensile Tests ◽  
Constant Current ◽  
Hydrogen Atoms ◽  
Laser Melting ◽  
Constant Current Density ◽  
Hydrogen Charging

A study was performed to investigate the hydrogen embrittlement behavior of 18-Ni 300 maraging steel produced by selective laser melting and subjected to different heat treatment strategies. Hydrogen was pre-charged into the tensile samples by an electro-chemical method at the constant current density of 1 A m−2 and 50 A m−2 for 48 h at room temperature. Charged and uncharged specimens were subjected to tensile tests and the hydrogen concentration was eventually analysed using quadrupole mass spectroscopy. After tensile tests, uncharged maraging samples showed fracture surfaces with dimples. Conversely, in H-charged alloys, quasi-cleavage mode fractures occurred. A lower concentration of trapped hydrogen atoms and higher elongation at fracture were measured in the H-charged samples that were subjected to solution treatment prior to hydrogen charging, compared to the as-built counterparts. Isothermal aging treatment performed at 460 °C for 8 h before hydrogen charging increased the concentration of trapped hydrogen, giving rise to higher hydrogen embrittlement susceptibility.

scholarly journals Moderate strain induced indirect bandgap and conduction electrons in MoS2 single layers

2019 ◽  
Vol 3 (1) ◽  
Author(s):  
János Pető ◽  
Gergely Dobrik ◽  
Gergő Kukucska ◽  
Péter Vancsó ◽  
Antal A. Koós ◽  
...  
Keyword(s):  
Charge Carrier ◽  
Fermi Level ◽  
Conduction Band ◽  
Carrier Density ◽  
Tensile Strain ◽  
Charge Carrier Density ◽  
Conduction Electrons ◽  
Metallic Character ◽  
Optical Bandgaps ◽  
Biaxial Tensile Strain

Abstract MoS2 single layers are valued for their sizeable direct bandgap at the heart of the envisaged electronic and optoelectronic applications. Here we experimentally demonstrate that moderate strain values (~2%) can already trigger an indirect bandgap transition and induce a finite charge carrier density in 2D MoS2 layers. A conclusive proof of the direct-to-indirect bandgap transition is provided by directly comparing the electronic and optical bandgaps of strained MoS2 single layers obtained from tunneling spectroscopy and photoluminescence measurements of MoS2 nanobubbles. Upon 2% biaxial tensile strain, the electronic gap becomes significantly smaller (1.45 ± 0.15 eV) than the optical direct gap (1.73 ± 0.1 eV), clearly evidencing a strain-induced direct to indirect bandgap transition. Moreover, the Fermi level can shift inside the conduction band already in moderately strained (~2%) MoS2 single layers conferring them a metallic character.

Hydrogen embrittlement of austenitic steels: electron approach

2013 ◽  
Vol 31 (2) ◽  
pp. 33-50 ◽  
Author(s):  
Valentin G. Gavriljuk ◽  
Bela D. Shanina ◽  
Vladyslav N. Shyvanyuk ◽  
Sergey M. Teus
Keyword(s):  
Hydrogen Embrittlement ◽  
Experimental Studies ◽  
Experimental Tests ◽  
Elastic Interaction ◽  
Plasticity Theory ◽  
Electron Structure ◽  
Austenitic Steels ◽  
Free Electrons ◽  
Steel Alloying ◽  
Hydrogen Resistance

AbstractA review of available hypotheses for hydrogen embrittlement (HE) in its relation to austenitic steels is presented. It is shown that the hydrogen-enhanced localized plasticity theory adequately describes the features of HE. Nevertheless, being developed within the frame of continuum mechanics, it overestimates the hydrogen-induced shielding of the elastic interaction between dislocations and does not take into account the hydrogen-induced change in the electron structure of austenitic steels. Ab initio calculations and experimental studies of the electron structure show that the hydrogen in austenitic steels increases the concentration of free electrons, nf, and the interpretation of available experimental data shows that when designing steel, alloying the steel with elements that decrease nf improves hydrogen resistance. Experimental tests are carried out, and their results are discussed. Based on the hydrogen-increased concentration of thermodynamic equilibrium vacancies in the interstitial solid solutions, a new model for hydrogen-induced shear localization is proposed.

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