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1 – 10 of 610Abstract
Purpose
This paper aims to verify the inhibition of the hydrogen permeation effect of the coating and to quantitatively and qualitatively characterize the coating-induced stress.
Design/methodology/approach
By means of slow strain rate tensile testing (SSRT) in humid air, thickness measurement, fracture morphology, cross-section morphology and surface morphology, hydrogen content measurements, flow stress difference method.
Findings
The results demonstrate that the mechanism of the inhibition of hydrogen embrittlement by the coating is mainly attributed to the repression of hydrogen permeation and the additional coating-induced compressive stress.
Originality/value
It is proven that the micro-arc oxidation (MAO) coating does inhibit hydrogen entry into the alloy, and the stress induced by the MAO coating is compressive stress, which can restrain the hydrogen embrittlement of the alloy. Therefore, the mechanism of the inhibition of hydrogen embrittlement is dominated by the mechanisms of both hydrogen permeation inhibition and coating-induced stress.
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Aqueous solutions which contain H2SO4, H2S or mixtures of H2S and NH3 are corrosive to carbon steel and other commonly used alloys. Therefore, titanium has been evaluated as a…
Abstract
Aqueous solutions which contain H2SO4, H2S or mixtures of H2S and NH3 are corrosive to carbon steel and other commonly used alloys. Therefore, titanium has been evaluated as a possible construction material in these environments. This paper summarizes the results of a study of the corrosion, galvanic and hydrogen embrittlement behaviour of titanium in aqueous sulfidic and sulfate solutions. Variables discussed include the effect of solution pH, temperature and solution composition on the corrosion and electro chemical behaviour including galvanic effects of titanium. This paper also considers the effect of pH, temperature and mechanical loading rate (strain‐rate) on the ductility and embrittlement of titanium.
Fan Bao, Kaiyu Zhang, Zhengrong Zhou, Wenli Zhang, Xiao Cai and Lin Zhang
The purpose of this paper is to demonstrate the effect of δ-ferrite on the susceptibility to hydrogen embrittlement of type 304 stainless steel in hydrogen gas environment.
Abstract
Purpose
The purpose of this paper is to demonstrate the effect of δ-ferrite on the susceptibility to hydrogen embrittlement of type 304 stainless steel in hydrogen gas environment.
Design/methodology/approach
The mechanical properties of as-received and solution-treated specimens were investigated by the test of tensile and fatigue crack growth (FCG) in 5 MPa argon and hydrogen.
Findings
The presence of δ-ferrite reduced the relative elongation and the relative reduction area (H2/Ar) of 304 stainless steel, indicating that δ-ferrite increased the susceptibility of hydrogen embrittlement in 304 stainless steel. Moreover, δ-ferrite promoted the fatigue crack initiation and propagation at the interface between δ-ferrite and austenite. The FCG tests were used to investigate the effect of δ-ferrite on the FCG rate in hydrogen gas environment, and it was found that δ-ferrite accelerated the FCG rate, which was attributed to rapid diffusion and accumulation of hydrogen around the fatigue crack tip through δ-ferrite in high-pressure hydrogen gas environment.
Originality/value
The dependence of the susceptibility to hydrogen embrittlement on δ-ferrite was first investigated in type 304 steel in hydrogen environment with high pressures, which provided the basis for the design and development of a high strength, hydrogen embrittle-resistant austenitic stainless steel.
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Gang Wang, Zihan Wang, Yue Zhang, GuangTao Xu, MingHao Zhao and Yanmin Li
The purpose of this paper is to find a new method to evaluate the hydrogen embrittlement performance of heterogeneous materials and thin film materials.
Abstract
Purpose
The purpose of this paper is to find a new method to evaluate the hydrogen embrittlement performance of heterogeneous materials and thin film materials.
Design/methodology/approach
The changes of hydrogen embrittlement properties of steel were studied by electrochemical hydrogen charging test and scratch test. The microstructure and properties of the alloy were analyzed by hardness tester, scanning electron microscope and three-dimensional morphology. The fracture toughness before and after hydrogen charging was calculated based on the scratch method.
Findings
The results showed that the hydrogen-induced hardening phenomenon occurs in the material after hydrogen charging. The scratch depth and width increased after hydrogen charging. The fracture toughness obtained by the scratch method showed that hydrogen reduces the fracture toughness of the material. The comparison error of fracture toughness calculated by indentation method was less than 5%.
Originality/value
The results show that the scratch method can evaluate the hydrogen embrittlement performance of the material. This method provides a possibility to evaluate the hydrogen embrittlement of thin-film and heterogeneous materials.
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This characteristic is important enough in aircraft maintenance to be covered separately. Considerably less embrittlement than that in bath plating is realized in selective…
Abstract
This characteristic is important enough in aircraft maintenance to be covered separately. Considerably less embrittlement than that in bath plating is realized in selective plating. With one proprietary solution, Cadmium LHE (Code SPS 5070), hydrogen embrittlement is almost negligible. Selectively plated nickel and nickel‐tungsten alloys also can be plated with so little hydrogen content that no baking for embrittle‐content that no baking for embrittlement relief is required.
M. Grujicic, V. Chenna, R. Galgalikar, J.S. Snipes, S. Ramaswami and R. Yavari
A simple economic analysis has revealed that in order for wind energy to be a viable alternative, wind-turbines (convertors of wind energy into electrical energy) must be able to…
Abstract
Purpose
A simple economic analysis has revealed that in order for wind energy to be a viable alternative, wind-turbines (convertors of wind energy into electrical energy) must be able to operate for at least 20 years, with only regular maintenance. However, wind-turbines built nowadays do not generally possess this level of reliability and durability. Specifically, due to the malfunction and failure of drive-trains/gear-boxes, many wind-turbines require major repairs after only three to five years in service. The paper aims to discuss these issues.
Design/methodology/approach
The subject of the present work is the so-called white etch cracking, one of the key processes responsible for the premature failure of gear-box roller-bearings. To address this problem, a multi-physics computational methodology is developed and used to analyze the problem of wind-turbine gear-box roller-bearing premature-failure. The main components of the proposed methodology include the analyses of: first, hydrogen dissolution and the accompanying grain-boundary embrittlement phenomena; second, hydrogen diffusion from the crack-wake into the adjacent unfractured material; third, the inter-granular fracture processes; and fourth, the kinematic and structural response of the bearing under service-loading conditions.
Findings
The results obtained clearly revealed the operation of the white-etch cracking phenomenon in wind-turbine gear-box roller-bearings and its dependence on the attendant loading and environmental conditions.
Originality/value
The present work attempts to make a contribution to the resolution of an important problem related to premature-failure and inferior reliability of wind-turbine gearboxes.
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D. Mukherjee, R. Rajmohan, B. Rathapan, V. Rajkumar and S. Raman
The paper discusses the aspect of probable stress induced embrittlement of 304 stainless steel stresses originating from thermal exposure, uniaxial tension, and reverse bending…
Abstract
The paper discusses the aspect of probable stress induced embrittlement of 304 stainless steel stresses originating from thermal exposure, uniaxial tension, and reverse bending, which have been simulated on the surface of SS plates of 1mm thickness, using conventional techniques. The physical and electrochemical properties of the treated SS materials have been followed up as a function of the corroding medium and also the type and extent of the stress interaction.
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Qin Kang, Yicheng Fan, Kun Zhang, Xiaolang Chen, Hongyu San, Yiqing Chen and Heming Zhao
With excellent mechanic properties and hydrogen embrittlement (HE) resistance, 12Cr2Mo1R(H) steel is suitable to make hot-wall hydrogenation reactors. However, longtime exposure…
Abstract
Purpose
With excellent mechanic properties and hydrogen embrittlement (HE) resistance, 12Cr2Mo1R(H) steel is suitable to make hot-wall hydrogenation reactors. However, longtime exposure to a harsh environment of high-pressure hydrogen at medium temperature in practical application would still induce severe hydrogen uptake and eventually damage the mechanical properties of the steel. The study aims to evaluate the HE resistance of the steel under different tensile strain rates after hydrogen charging and analyze the hydrogen effect from atomic level.
Design/methodology/approach
This research studied the HE properties of 12Cr2Mo1R(H) steel by slow strain rate tests. Meanwhile, the effect of hydrogen on the structures and the mechanical properties of the simplified models of the steel was also investigated by first-principle calculations.
Findings
Experimental results showed that after hydrogen pre-charging in this work, hydrogen had little effect on the microstructure of the steel. The elongations and reduction of cross-sectional area of the samples reduced a lot, by contrast, the yield and tensile strengths changed slightly. The 12Cr2Mo1R(H) steel was not very susceptible to HE with a maximum embrittlement index of about 20.00%. First principles calculation results showed that after H dissolution, lattice distortion occurred and interstitial H atoms would preferentially occupy the tetrahedral interstitial site in bcc-Fe crystal and increase the stability of the supercells. With the increase of H atoms added into the simplified model, the steel still possessed a good ductility and toughness at a low hydrogen concentration, while the material would become brittle as the concentration of hydrogen continued to increase.
Originality/value
These finds can provide valuable information for subsequent HE studies on this steel.
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Kun Zhang, Yicheng Fan, Xiaowei Luo, Xiaolang Chen, Chaolei Ban, Heming Zhao and Yiqing Chen
12Cr2Mo1R(H) steel is commonly used to make hot-wall hydrogenation reactors given its excellent mechanical properties and hydrogen embrittlement (HE) resistance. Longtime exposure…
Abstract
Purpose
12Cr2Mo1R(H) steel is commonly used to make hot-wall hydrogenation reactors given its excellent mechanical properties and hydrogen embrittlement (HE) resistance. Longtime exposure to high-pressure hydrogen at medium temperature would still severely damage the mechanical properties of the Cr-Mo steel with surface HICs caused by hydrogen adsorption and hydrogen uptake. The mechanisms of HE remain controversial and have not been fully understood so far.
Design/methodology/approach
The HE of the steel was investigated by slow strain rate test at different strain rates with in situ hydrogen charging. The diffusion coefficient of hydrogen in the steel is measured by electrochemical technology of hydrogen permeation. HIC cracks of the fractured specimens were captured with field emission SEM equipped with an electron backscatter diffraction system.
Findings
Results showed that the hydrogen led to the plasticity of the samples reduced significantly, together with the distinct work hardening behavior induced by hydrogen charging during plastic flow stage. The fracture of in situ charged sample changes from quasi-cleavage to intergranular fracture with the decreasing of strain rates, which indicates that the steel become more susceptible to hydrogen. High densities of dislocations and deformation are found around the crack, where grains are highly sensitive to HIC. Grains with different Taylor factor are more susceptible to intergranular crack.
Originality/value
The results of the study would be helpful to a safer application of the steel.
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R.J. WANHILL and W.J. van de VET
Introduction This report deals with two important causes of service failures in high strength steels: stress corrosion and hydrogen embrittlement. These failure modes are often…
Abstract
Introduction This report deals with two important causes of service failures in high strength steels: stress corrosion and hydrogen embrittlement. These failure modes are often difficult to distinguish from one another fractographically, and sometimes the macroscopic and metallagraphic interpretation is also open to doubt.