Modelling the combined effects of hydrogen traps and surface films on hydrogen permeation in ferritic steels

2020 ◽  
Vol 67 (2) ◽  
pp. 240-247
Author(s):  
Huihui Zhi ◽  
Haiyang Yu ◽  
Lei Gao ◽  
Zhiliang Zhang ◽  
Yanjing Su
Keyword(s):  
Oxide Film ◽  
Hydrogen Concentration ◽  
Hydrogen Diffusion ◽  
Hydrogen Permeation ◽  
Steel Substrate ◽  
Ferritic Steels ◽  
Surface Films ◽  
Material System ◽  
Combined Effects ◽  
Content Type

Purpose The purpose of this study is to develop a model extending Oriani’s formula by introducing a normalised concentration to simulate hydrogen diffusion in a multi-material system such as coated steels, under the presence of traps. Design/methodology/approach Implemented through the finite element method based on the analogy between mass diffusion and heat transfer, the governing equation was applied to investigate the combined effects of hydrogen traps and surface oxide films on hydrogen permeation in ferritic steels. Findings This study shows that the effective diffusivity varies over several orders of magnitude depending on the traps and films. This explains the divergence of measured hydrogen diffusivities in steels. It is revealed that hydrogen permeation in steels with Pd or Ni film is a trapping-dominant transport process, while hydrogen permeation in steel with oxide film is a process controlled by both trapping effect and retarding effect of oxide film. The oxide film enhances total hydrogen concentration within the steel substrate and is therefore detrimental. The Pd or Ni film has a little influence on total hydrogen concentration distribution depending on trapping energy. Originality/value Hydrogen flux curves and transient hydrogen concentration distributions can be directly obtained through the developed model. The proposed approach can also be extended to investigate other interstitial (i.e. carbon, oxygen and nitrogen) diffusion with traps revisited in complex systems.

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.

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.

Performance of gas nanosensor in 1-4 per cent hydrogen concentration

Sensor Review ◽  
2019 ◽  
Vol 39 (4) ◽  
pp. 622-628 ◽  
Author(s):  
Ghobad Behzadi Pour ◽  
Leila Fekri Aval ◽  
Parisa Esmaili
Keyword(s):  
Oxide Film ◽  
Gas Sensor ◽  
Hydrogen Concentration ◽  
Response Times ◽  
Fast Response ◽  
Hydrogen Gas ◽  
Oxide Semiconductor ◽  
Content Type ◽  
Hydrogen Gas Sensors ◽  
Mos Sensor

Purpose This study aims to investigate the fabrication of hydrogen gas sensor based on metal–oxide–semiconductor (MOS) microstructure. The palladium nanoparticles (PdNPs) as gate metal have been deposited on the oxide film using spin coating. Design/methodology/approach The PdNPs and the surface of oxide film were analyzed using Transmission electron microscopy. The capacitance-voltage (C-V) curves for the MOS sensor in 1, 2 and 4 per cent hydrogen concentration and in 100 KHz frequency at the room temperature were reported. Findings The response times for 1, 2 and 4 per cent hydrogen concentration were 2.5 s, 1.5 s and 1 s, respectively. The responses (R per cent) of MOS sensor to 1, 2 and 4 per cent hydrogen concentration were 42.8, 47.3 and 52.6 per cent, respectively. Originality/value The experimental results demonstrate that the MOS hydrogen gas sensor based on the PdNPs gate, shows the fast response and recovery compared to other hydrogen gas sensors based on the Pd.

Hydrogen diffusion kinetics under different conditions applied to VT6 alloy

2020 ◽  
pp. 98-107
Author(s):  
E. I. Maslikova ◽  
V. D. Andreeva ◽  
E. L. Alekseeva ◽  
Yu. A. Yakovlev
Keyword(s):  
Heat Treatment ◽  
Oxide Film ◽  
Titanium Alloys ◽  
Hydrogen Diffusion ◽  
Heat Treating ◽  
Protective Atmosphere ◽  
Diffusion Kinetics ◽  
Hydrogen Charging ◽  
Hydride Formation ◽  
Different Types

Research of hydrogen diffusion in VT6 alloy is carried out considering different types of heat treating and hydrogen charging. The influence of microalloying on the susceptibility to hydride formation and embrittlement of titanium alloys is analyzed, and also effects of an oxide film on hydrogen charging during heat treatment without protective atmosphere, are studied.

Hydrogen permeation through a slab sample in the case of high hydrogen concentration

2006 ◽  
Vol 496 (2) ◽  
pp. 735-739 ◽  
Author(s):  
Maurizio Dapor ◽  
Antonio Miotello ◽  
Arturo Sabbioni
Keyword(s):  
Hydrogen Concentration ◽  
Hydrogen Permeation ◽  
High Hydrogen

Influence of Heat Treatment on Characteristic Behavior of Co-Based Alloy Hardfacing Coatings Deposited by Plasma Transferred Arc Welding

2011 ◽  
Vol 462-463 ◽  
pp. 593-598 ◽  
Author(s):  
Hong Xia Deng ◽  
Hui Ji Shi ◽  
Seiji Tsuruoka ◽  
Hui Chen Yu ◽  
Bin Zhong
Keyword(s):  
Residual Stresses ◽  
Vickers Hardness ◽  
Arc Welding ◽  
Steel Substrate ◽  
Heat Treatments ◽  
Material System ◽  
Coating Surface ◽  
Plasma Transferred Arc ◽  
Transferred Arc ◽  
Plasma Transferred Arc Welding

The Plasma transferred arc welding (PTAW) is widely used for hardfacing components exposed to severe conditions. Without post welding heat treatments, large tensile residual stresses remain in the hardfacing coating, which is detrimental. In this paper, a set of post welding heat treatments was evaluated for the heat-resistant steel substrate – Co-based alloy hardfacing coating system. Microstructural and mechanical properties, including the chemical phases of coating surface, the microstructure of coating surface, the Vickers hardness and the residual welding stress, were investigated before and after the heat treatments. Results revealed that during the heat treatments, some elements reprecipitated and the secondary carbide Cr23C6 was formed. After the treatments, a more regular structure and a higher Vickers hardness were obtained. Moreover, the tensile residual stresses in the coating decreased significantly. Therefore, it can be inferred that the post welding heat treatments employed in this paper were proper for this material system.

Optimization of chemical mechanical polishing parameters on surface roughness of steel substrate with aluminum nanoparticles via Taguchi approach

2014 ◽  
Vol 66 (6) ◽  
pp. 685-690 ◽  
Author(s):  
De-Xing Peng
Keyword(s):  
Flow Rate ◽  
Chemical Mechanical Polishing ◽  
Steel Substrate ◽  
Value Added ◽  
Mechanical Polishing ◽  
Slurry Flow ◽  
Average Roughness ◽  
Content Type ◽  
Optimization Parameters ◽  
Slurry Flow Rate

Purpose – The purpose of this paper is to investigate the effects of abrasive contents, oxidizer contents, slurry flow rate and polishing time in achieving a mirror-like finish on polished surfaces. Chemical mechanical polishing (CMP) is now widely used in the aerospace industry for global planarization of large, high value-added components. Design/methodology/approach – Optimal parameters are applied in experimental trials performed to investigate the effects of abrasive contents, oxidizer contents, slurry flow rate and polishing time in achieving a mirror-like finish on polished surfaces. Taguchi design experiments are performed to optimize the parameters of CMP performed in steel specimens. Findings – Their optimization parameters were found out; the surface scratch, polishing fog and remaining particles were reduced; and the flatness of the steel substrate was guaranteed. The average roughness (Ra) of the surface was reduced to 6.7 nm under the following process parameters: abrasive content of 2 weight per cent, oxidizer content of 2 weight per cent, slurry flow rate of 100 ml/min and polishing time of 20 min. Originality/value – To meet the final process requirements, the CMP process must provide a good planarity, precise selectivity and a defect-free surface. Surface planarization of components used to fabricate aerospace devices is achieved by CMP process, which enables global planarization by combining chemical and mechanical interactions.

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.

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

2009 ◽  
Vol 283-286 ◽  
pp. 225-230 ◽  
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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