scholarly journals Effect of Microstructure on Hydrogen Permeation in EA4T and 30CrNiMoV12 Railway Axle Steels

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 164 ◽  
Author(s):  
Tingzhi Si ◽  
Yunpeng Liu ◽  
Qingan Zhang ◽  
Dongming Liu ◽  
Yongtao Li
Keyword(s):  
Activation Energy ◽  
Hydrogen Diffusion ◽  
Hydrogen Permeation ◽  
Martensitic Structure ◽  
Hydrogen Diffusivity ◽  
High Hydrogen ◽  
Railway Axle ◽  
Effective Hydrogen ◽  
Trapping Sites ◽  
Effect Of Microstructure

A comparative study was conducted to reveal the effect of microstructure on hydrogen permeation in the EA4T and 30CrNiMoV12 railway axle steels. Unlike the EA4T with its sorbite structure, 30CrNiMoV12 steel shows a typical tempered martensitic structure, in which a large number of fine, short, rod-like, and spherical carbides are uniformly dispersed at boundaries and inside laths. More importantly, this structure possesses plentifully strong hydrogen traps, such as nanosized Cr7C3, Mo2C, VC, and V4C3, thus resulting in a high density of trapping sites (N = 1.17 × 1022 cm−3). The hydrogen permeation experiments further demonstrated that, compared to EA4T, the 30CrNiMoV12 steel not only delivered minimally effective hydrogen diffusivity but also had a high hydrogen concentration. The activation energy for hydrogen diffusion of the 30CrNiMoV12 steel was greatly increased from 23.27 ± 1.94 of EA4T to 47.82 ± 2.14 kJ mol−1.

Alloying Effects on the Hydrogen Diffusivity during Hydrogen Permeation through Nb-Based Hydrogen Permeable Membranes

2010 ◽  
Vol 297-301 ◽  
pp. 1091-1096 ◽  
Author(s):  
Hiroshi Yukawa ◽  
G.X. Zhang ◽  
Masahiko Morinaga ◽  
T. Nambu ◽  
Yoshihisa Matsumoto
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Hydrogen Diffusion ◽  
Hydrogen Permeation ◽  
Hydrogen Permeability ◽  
Hydrogen Diffusivity ◽  
Hydrogen Flux ◽  
Pure Niobium ◽  
Hydrogen Diffusion Coefficient ◽  
Alloying Effects

The hydrogen solubility and the hydrogen permeability have been measured for Nb-based alloys in order to investigate the alloying effects on the hydrogen diffusivity during hydrogen permeation. The hydrogen diffusion coefficient during hydrogen permeation is estimated from a linear relationship between the normalized hydrogen flux, , and the difference of hydrogen concentration, C, between the inlet and the outlet sides of the membrane. It is found that the hydrogen diffusion coefficient during the hydrogen permeation is increased by alloying ruthenium or tungsten into niobium. On the other hand, the activation energy for hydrogen diffusion in pure niobium under the practical permeation condition is much higher than the reported values measured for dilute hydrogen solid solutions. It is interesting that the activation energy for hydrogen diffusion decreases by the addition of ruthenium or tungsten into niobium.

scholarly journals The Positive Role of Nanometric Molybdenum–Vanadium Carbides in Mitigating Hydrogen Embrittlement in Structural Steels

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7269
Author(s):  
Luis Borja Peral ◽  
Inés Fernández-Pariente ◽  
Chiara Colombo ◽  
Cristina Rodríguez ◽  
Javier Belzunce
Keyword(s):  
Diffusion Coefficient ◽  
Hydrogen Embrittlement ◽  
Hydrogen Diffusion ◽  
Hydrogen Permeation ◽  
Fatigue Crack Propagation Rate ◽  
Hydrogen Trapping ◽  
Hydrogen Atoms ◽  
High Hydrogen ◽  
Internal Hydrogen ◽  
Trapping Sites

The influence of hydrogen on the fracture toughness and fatigue crack propagation rate of two structural steel grades, with and without vanadium, was evaluated by means of tests performed on thermally precharged samples in a hydrogen reactor at 195 bar and 450 °C for 21 h. The degradation of the mechanical properties was directly correlated with the interaction between hydrogen atoms and the steel microstructure. A LECO DH603 hydrogen analyzer was used to study the activation energies of the different microstructural trapping sites, and also to study the hydrogen eggresion kinetics at room temperature. The electrochemical hydrogen permeation technique was employed to estimate the apparent hydrogen diffusion coefficient. Under the mentioned hydrogen precharging conditions, a very high hydrogen concentration was introduced within the V-added steel (4.3 ppm). The V-added grade had stronger trapping sites and much lower apparent diffusion coefficient. Hydrogen embrittlement susceptibility increased significantly due to the presence of internal hydrogen in the V-free steel in comparison with tests carried out in the uncharged condition. However, the V-added steel grade (+0.31%V) was less sensitive to hydrogen embrittlement. This fact was ascribed to the positive effect of the precipitated nanometric (Mo,V)C to alleviate hydrogen embrittlement. Mixed nanometric (Mo,V)C might be considered to be nondiffusible hydrogen-trapping sites, in view of their strong hydrogen-trapping capability (~35 kJ/mol). Hence, mechanical behavior of the V-added grade in the presence of internal hydrogen was notably improved.

Investigation of Hydrogen Diffusion Characteristics of the Heat Affected Zone of 2.25Cr-1Mo-0.25V Steel by an Electrochemical Permeation Method

2019 ◽  
Author(s):  
Xin Song ◽  
Zelin Han ◽  
Bin Liu ◽  
Mu Qin ◽  
Yuancai Duo ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Hydrogen Concentration ◽  
Heat Affected Zone ◽  
Hydrogen Diffusion ◽  
Trap Density ◽  
Hydrogen Diffusivity ◽  
Hydrogen Flux ◽  
Hydrogen Trap ◽  
Diffusion Characteristics ◽  
Effective Hydrogen

Abstract The heat affected zone (HAZ) of 2.25Cr-1Mo-0.25V welded joint is a critical part for the safety of hydrogenation reactors. Hydrogen has a significant effect on the HAZ, studying hydrogen diffusion characteristics, such as: hydrogen flux and the effective hydrogen diffusivity has a remarkable value in investigating the hydrogen-induced material degradation mechanisms. In this work, an electrochemical permeation method was applied to study the hydrogen diffusion characteristics of HAZ. Then, the metallographic microscope and a software “Image J” were used to analyze the density of grain boundaries of HAZ. The effect of the post–weld heat treatment (PWHT, i.e. annealing) on the hydrogen diffusion characteristics of HAZ was also been investigated. The results show that after PWHT, the effective hydrogen diffusivity of HAZ increases from 1.63 × 10−7cm2·s−1 to 3.68 × 10−7cm2·s−1, the hydrogen concentration decreases from 1.92 × 10−4mol·cm−3 to 1.09 × 10−4mol·cm−3, and the hydrogen trap density decreases from 3.00 × 1026m−3 to 0.76 × 1026m−3. Thus, PWHT can significantly reduce density of grain boundaries, thereby reducing the hydrogen trap density, enhancing the hydrogen diffusivity and reducing the hydrogen concentration.

scholarly journals Hydrogen Diffusivity in Different Microstructures of 42CrMo4 Steel

Hydrogen ◽  
2021 ◽  
Vol 2 (4) ◽  
pp. 414-427
Author(s):  
Atif Imdad ◽  
Alfredo Zafra ◽  
Victor Arniella ◽  
Javier Belzunce
Keyword(s):  
Diffusion Coefficient ◽  
Hydrogen Diffusion ◽  
Hydrogen Permeation ◽  
Ferritic Steels ◽  
Hydrogen Diffusivity ◽  
Hydrogen Atoms ◽  
Hydrogen Diffusion Coefficient ◽  
Microstructural Defects ◽  
42Crmo4 Steel

It is well known that the presence of hydrogen decreases the mechanical properties of ferritic steels, giving rise to the phenomenon known as hydrogen embrittlement (HE). The sensitivity to HE increases with the strength of the steel due to the increase of its microstructural defects (hydrogen traps), which eventually increase hydrogen solubility and decrease hydrogen diffusivity in the steel. The aim of this work is to study hydrogen diffusivity in a 42CrMo4 steel submitted to different heat treatments—annealing, normalizing and quench and tempering—to obtain different microstructures, with a broad range of hardness levels. Electrochemical hydrogen permeation tests were performed in a modified Devanathan and Stachursky double-cell. The build-up transient methodology allowed the determination of the apparent hydrogen diffusion coefficient, Dapp, and assessment of its evolution during the progressive filling of the microstructural hydrogen traps. Consequently, the lattice hydrogen diffusion coefficient, DL, was determined. Optical and scanning electron microscopy (SEM) were employed to examine the steel microstructures in order to understand their interaction with hydrogen atoms. In general, the results show that the permeation parameters are strongly related to the steel hardness, being less affected by the type of microstructure.

scholarly journals Hydrogen Diffusion and Its Effect on Hydrogen Embrittlement in DP Steels With Different Martensite Content

2020 ◽  
Vol 7 ◽  
Author(s):  
Zhen Wang ◽  
Jing Liu ◽  
Feng Huang ◽  
Yun-jie Bi ◽  
Shi-qi Zhang
Keyword(s):  
Hydrogen Embrittlement ◽  
Hydrogen Diffusion ◽  
Hydrogen Permeation ◽  
Hydrogen Atoms ◽  
Martensite Content ◽  
Measurement Results ◽  
Dp Steels ◽  
Logarithmic Relationship ◽  
Diffusion Of Hydrogen ◽  
Effective Hydrogen

The hydrogen diffusion behavior and hydrogen embrittlement susceptibility of dual phase (DP) steels with different martensite content were investigated using the slow strain-rate tensile test and hydrogen permeation measurement. Results showed that a logarithmic relationship was established between the hydrogen embrittlement index (IHE) and the effective hydrogen diffusion coefficient (Deff). When the martensite content is low, ferrite/martensite interface behaves as the main trap that captures the hydrogen atoms. Also, when the Deff decreases, IHE increases with increasing martensite content. However, when the martensite content reaches approximately 68.3%, the martensite grains start to form a continuous network, Deff reaches a plateau and IHE continues to increase. This is mainly related to the reduction of carbon content in martensite and the length of ferrite/martensite interface, which promotes the diffusion of hydrogen atoms in martensite and the aggregation of hydrogen atoms at the ferrite/martensite interface. Finally, a model describing the mechanism of microstructure-driven hydrogen diffusion with different martensite distribution was established.

Hydrogen Diffusion in Quartz: A Molecular Dynamics Investigation

1995 ◽  
Vol 408 ◽  
Author(s):  
A. Bongiorno ◽  
L. Colombo
Keyword(s):  
Activation Energy ◽  
Molecular Dynamics ◽  
Diffusion Coefficient ◽  
Hydrogen Diffusion ◽  
Diffusion Path ◽  
Arrhenius Law ◽  
Hydrogen Diffusivity ◽  
Temperature Dependent ◽  
Crystalline Quartz ◽  
Wide Range

AbstractWe present a molecular dynamics investigation on hydrogen diffusivity in crystalline quartz by computing the diffusion coefficient over a wide range of temperatures (700K < T < 1500K) and by characterizing the diffusion path and mechanism. Our main findings are: (i) hydrogen diffusion is anisotropically confined along the c-axis in α- and β-quartz; (ii) hydrogen diffuses through a jump-like mechanism; (iii) the temperature-dependent diffusivity follows an Arrhenius law with activation energy of 0.56 eV and 0.27 eV for α-and β-quartz, respectively.

Hydrogen Migration In Phosphorous Doped Polycrystalline Silicon

1998 ◽  
Vol 513 ◽  
Author(s):  
N. H. Nickel ◽  
I. Kaiser
Keyword(s):  
Activation Energy ◽  
Polycrystalline Silicon ◽  
Hydrogen Diffusion ◽  
Chemical Potential ◽  
Effective Diffusion ◽  
High Hydrogen ◽  
Deep Traps ◽  
Level Model ◽  
Increasing Temperature ◽  
Two Level Model

ABSTRACTHydrogen diffusion in phosphorous doped polycrystalline silicon was investigated by deuterium diffusion experiments. The presence of phosphorous enhances hydrogen diffusion. For high hydrogen concentrations the activation energy of the effective diffusion-coefficient amounts to 0.25-0.35 eV. At low hydrogen concentrations diffusion is governed by deep traps that are present in an appreciable concentration of 6×108 - 1019 cm−3. The hydrogen chemical-potential, 9H, decreases with increasing temperature at a rate of ˜ 0.002 eV/K. The data are discussed in terms of a two-level model used to describe hydrogen diffusion in amorphous and undoped polycrystalline silicon.

scholarly journals Correlation between Microstructure and Hydrogen Degradation of 690 MPa Grade Marine Engineering Steel

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 851
Author(s):  
Heng Ma ◽  
Huiyun Tian ◽  
Juncheng Xin ◽  
Zhongyu Cui
Keyword(s):  
Crack Propagation ◽  
Base Metal ◽  
Hydrogen Diffusion ◽  
Hydrogen Permeation ◽  
Steel Substrate ◽  
Phase Interface ◽  
Grain Structure ◽  
Hydrogen Degradation ◽  
Two Phase ◽  
Annealed Steel

Electrochemical H charging, hydrogen permeation, and hydrogen-induced cracking (HIC) behavior of 690 MPa grade steel substrate and different heat-treatment states (annealed, quenched, normalized, tempered) are investigated by cyclic voltammetry (CV), hydrogen permeation, electrochemical H charging, and slow strain rate tensile test (SSRT). The results show that hydrogen diffuses through the steel with the highest rate in base metal and the lowest rate in annealed steel. The hydrogen-induced cracks in base metal show obvious step shape with tiny cracks near the main crack. The cracks of annealed steel are mainly distributed along pearlite. The crack propagation of quenched steel is mainly transgranular, while the hydrogen-induced crack propagation of tempered steel is along the prior austenite grain boundary. HIC sensitivity of base metal is the lowest due to its fine homogeneous grain structure, small hydrogen diffusion coefficient, and small hydrogen diffusion rate. There are many hydrogen traps in annealed steel, such as the two-phase interface which provides accommodation sites for H atoms and increases the HIC susceptibility.

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