Hydrogen Embrittlement Of High Strength Steels Research Articles

In-situ measurement of hydrogen entry and hydrogen embrittlement of steel by atmospheric corrosion

Hydrogen entry and hydrogen embrittlement of high-strength steel in atmospheric corrosion environment was investigated using an in-situ hydrogen permeation technique and a strain gage method, respectively. The hydrogen concentration increased at the beginning of corrosion and when the corrosion reaction was accelerated, such as when a typhoon approached. The hydrogen embrittlement occurred when the surface hydrogen concentration exceeded the critical hydrogen concentration. It is directly demonstrated that hydrogen embrittlement crack initiation, arrest, and propagation are repeated accompanied with hydrogen entry and release due to environmental changes, leading to final fracture.

Hydrogen embrittlement of high-strength steels in thiosulphate solutions

ABSTRACT The susceptibility to hydrogen embrittlement of supermartensitic stainless steel (S13Cr), martensitic-ferritic stainless steel (17Cr), carbon steel (P110) and austenitic-ferritic stainless steels (2205 and 2507) was evaluated by slow strain rate tests using a modified NACE TM-0177 solution, with 10–3M NaS2O3 substituting the saturated H2S standard solution. Tests were conducted at 25°C, pH 2.7 and under galvanostatic polarisation with a cathodic charging of 10 mA/cm2. S13Cr, 17Cr, P110 and 2507 steels were susceptible to hydrogen embrittlement inthiosulphate, with S13Cr and 17Cr being the most sensitive to this mechanism, while 2205 showed no sign of ductility loss. This harmful effect was attributed to the hydrogen sulphide generated from thiosulphate.

Sacrificial Zn–Ni coatings by electroplating and hydrogen embrittlement of high-strength steels

Abstract A review of sacrificial Zn–Ni electroplating coatings on high-strength steels is presented. These steels are used for heavy structural applications such as landing gears, etc., that are subjected to high stresses and corrosive environments in service. The electroplating process involving aqueous electrolytes invariably produces hydrogen. The emitted hydrogen can diffuse into substrate steel, contributing to the delayed failures by hydrogen embrittlement. Microstructural inhomogeneities arising from the heat treatments and defects produced during coatings and those inherently present in the steels can trap hydrogen emitted during plating. Dissolved and trapped hydrogen can slowly diffuse to the stress concentrations or crack tips, contributing to the delayed structural failures. Baking after plating helps to eliminate hydrogen to some extent, though it may introduce some thermomechanical stresses at the bimaterial interfaces. This review discusses a) the current state of sacrificial Zn–Ni coatings, b) their protection against corrosion of the substrate, c) the associated hydrogen embrittlement predominately under cyclic loads, and d) recent advances in terms of the compositionally modulated coatings for enhanced protection.

Effect of in-situ nanoparticles on the mechanical properties and hydrogen embrittlement of high-strength steel

We investigated the critical influence of in-situ nanoparticles on the mechanical properties and hydrogen embrittlement (HE) of high-strength steel. The results reveal that the mechanical strength and elongation of quenched and tempered steel (919 MPa yield strength, 17.11% elongation) are greater than those of hot-rolled steel (690 MPa yield strength, 16.81% elongation) due to the strengthening effect of in-situ Ti3O5-Nb(C,N) nanoparticles. In addition, the HE susceptibility is substantially mitigated to 55.52%, approximately 30% lower than that of steels without in-situ nanoparticles (84.04%), which we attribute to the heterogeneous nucleation of the Ti3O5 nanoparticles increasing the density of the carbides. Compared with hard TiN inclusions, the spherical and soft Al2O3-MnS core—shell inclusions that nucleate on in-situ Al2O3 particles could also suppress HE. In-situ nanoparticles generated by the regional trace-element supply have strong potential for the development of high-strength and hydrogen-resistant steels.

Effects of Cu addition on resistance to hydrogen embrittlement in 1 GPa-grade duplex lightweight steels

Hydrogen embrittlement (HE) has arisen as one of main issues for developing high-strength lightweight steels. The precipitation of fine particles providing as stable H-trapping sites is preferred to overcome the intrinsic HE of high-strength steels. However, studies on HE in high-strength lightweight steels along with roles of B2 particles have not been reported yet. In this study, three Fe–0.8C–15Mn–7Al–(0,1,3)Cu duplex lightweight steels were fabricated, and their resistance to HE was evaluated. Roles of Cu addition were investigated by the loss of elongation measured from slow-strain-rate tensile tests and by the concentration and diffusivity of H measured from electrochemical H permeation tests. The Cu addition results in the decreased elongation loss and the lower concentration and effective diffusivity of reversible H, indicating the higher resistance to HE. The unraveled mechanism is that the Cu addition increases the fraction of austenite, where the diffusivity of H is much lower than ferrite, and decreases the strain localization along ferrite grains to reduce the internal diffusion of H during deformation. In addition, it promotes the formation of complex semi-coherent Cu-rich B2 particles, which provides misfit dislocations at interfaces as stable and irreversible H-trapping sites. The B2 particles preferentially nucleated at reversible sites such as grain boundaries and phase interfaces promote a transition from reversible to irreversible sites, which further reduces the diffusivity of H. The present work, thus, would suggest the Cu addition to enhance both tensile properties and resistance to HE for designing high-strength lightweight steels.

Hydrogen Embrittlement for High-Strength Steel Electroplated with Zinc-Based Coatings

Hydrogen Embrittlement for High-Strength Steel Electroplated with Zinc-Based Coatings

Monitoring fracture of high-strength steel under tensile and constant loading using acoustic emission analysis

In the aeronautical industry, many critical components are made of high-strength steels. These steels have high tensile strength but are sensitive to corrosion and to the hydrogen embrittlement phenomenon. This study examines how acoustic emission could be used to detect hydrogen embrittlement of high-strength steels and reduce the duration of the standard test. Acoustic emission (AE) was coupled with sustained load testing at 75% of the material fracture stress for 200 h as prescribed in ASTM standard F519. Tensile strength tests were also conducted to determine the mechanical characteristics and acoustic signature of the mechanisms of damage that progress to material fracture. The results show that the time required for sustained load tests can be shortened, based on the emission of acoustic events by the hydrogen-embrittled test coupons from the beginning of the test and after certain lengths of time. Scanning electron microscopy imaging of the fracture surfaces showed a very good correlation with the recorded acoustic event signatures.

Increased resistance to hydrogen embrittlement in high-strength steels composed of granular bainite

This paper presents two high-strength steels composed of granular bainite microstructure that have higher extrinsic resistance to hydrogen embrittlement (HE) than conventional tempered-martensite steel, because the granular bainite steel traps less hydrogen than tempered-martensite steel. However, the granular bainite steels had lower intrinsic HE resistance than tempered-martensite steel because hydrogen in granular bainite steels becomes concentrated at microstructures composed of martensite islands and retained austenite. The granular bainite steels with less sulfur showed better HE properties, because S degrades grain-boundary strength. Since the extrinsic properties correspond to the HE resistance that is relevant in industry, granular bainite steels are suitable for applications in hydrogen environment.

Studies of Evaluation of Hydrogen Embrittlement Property of High-Strength Steels with Consideration of the Effect of Atmospheric Corrosion

Hydrogen embrittlement of high-strength steels was investigated by using slow strain rate test (SSRT) of circumferentially notched round bar specimens after hydrogen precharging. On top of that, cyclic corrosion tests (CCT) and outdoor exposure tests were conducted prior to SSRT to take into account the effect of hydrogen uptake under atmospheric corrosion for the evaluation of the susceptibility of high-strength steels. Our studies of hydrogen embrittle properties of high-strength steels with 1100 to 1500 MPa of tensile strength and a prototype ultrahigh-strength steel with 1760 MPa containing hydrogen traps using those methods are reviewed in this article. A power law relationship between notch tensile strength of hydrogen-precharged specimens and diffusible hydrogen content has been found. It has also been found that the local stress and the local hydrogen concentration are controlling factors of fracture. The results obtained by using SSRT after CCT and outdoor exposure test were in good agreement with the hydrogen embrittlement fracture property obtained by means of long-term exposure tests of bolts made of the high-strength steels.

HYDROGEN EMBRITTLEMENT: RECENT INDIAN RESEARCH AND PERSPECTIVES

This article provides an overview of hydrogen embrittlement (HE) research and related investigations carried out by Indian researchers over approximately the last two decades. There is a substantial body of work on steels, on certain intermetallics and on hydride forming alloy systems. Work on HE of High strength steels, pipeline grade steels, Zircalloys and iron-aluminides have been more popular amongst Indian researchers, often on account of the specific use of these materials in hydrogen environments in practical situations, than for other alloy systems. Indian researchers have addressed a variety of issues like microstructural and compositional influence on HE, microstructure tailoring, alloy modifications and alloy development strategies to counter HE, analyses of HE failures in industries, and others. Work has been initiated to provide life prediction methodologies for hydrogen degradation, but comprehensive efforts are few. Similarly surface engineering strategies to counter HE have been relatively neglected by Indian researchers.

Hydrogen embrittlement of high-strength steel submitted to slow strain rate testing studied by nuclear resonance reaction analysis and neutron diffraction

Embrittlement of high-strength steel is known to be caused by hydrogen penetration into the network of the metal. However, the penetration mechanism of hydrogen into the steel is still under discussion, as it is not so easy to detect and measure the hydrogen in steels. In this paper, relatively large commercial cold drawn pearlitic steel wires have been submitted to stress corrosion cracking under different environments. After these tests, Nuclear Resonance Reaction Analysis, NRRA, has been used to detect the presence of the hydrogen and its quantity, which has confirmed the presence of H in the case of brittle fracture. In addition, once the presence of hydrogen has been confirmed, the penetration of the hydrogen into the unit cell of the ferrite has been deduced from the analysis of the steels by neutron diffraction, from the shift of the d-spacing after the experiments. The application of NRRA and Neutron Diffraction techniques have been shown as very promising techniques to study the mechanisms of the embrittlement of the steel to the hydrogen present in the metallic lattice.

The Use of Crack-Tip Opening Displacement for Testing of the Hydrogen Embrittlement of High-Strength Steels

Stress-corrosion cracks are, as a rule, brittle and often encountered under stresses much lower than the yield strength. For this reason, the methods of linear elastic fracture mechanics (LEFM) can be used for the investigation of stress-corrosion cracking (SCC). However, in some cases, these methods are inapplicable, and it is necessary to use the methods of so-called elastoplastic fracture mechanics (EPFM). In the EPFM approach, the J-integral is the most commonly used parameter for correlating crack initiation and propagation but the crack-tip opening displacement (CTOD) and crack-tip opening angle (CTOA) prove to be promising alternatives, especially for thin-sheet materials. Since both these parameters are connected with the crack geometry and, hence, reflect the level of strain at the crack tip, they appear to be useful correlation parameters for the cases of SCC, where the level of strain in the vicinity of the crack tip and, in particular, the strain rate, are the determining variables of the process. The hydrogen embrittlement of a higher-strength structural steel and welded joints of a C-Mn steel is assessed by using the CTOA and CTOD methodologies. In constant-extension-rate tests (CERT), fatigue precracked specimens were loaded with various low strain rates and electrolytically charged with hydrogen. It was discovered that hydrogen embrittlement significantly affects the crack-growth resistance curves (R-curves) thus generated and the opening angle for which the crack propagates into the material.

Effect of formation of surface hydroxide on hydrogen permeability of iron membranes and hydrogen embrittlement of high-strength steels

Effect of formation of surface hydroxide on hydrogen permeability of iron membranes and hydrogen embrittlement of high-strength steels

Development of diagnostic expert system for environmentally assisted cracking(EXENAC) and importance evaluation of knowledge in inference.

The expert system which diagnoses the sensitivity of environmentally assisted cracking (EXENAC ; EXpert system for ENvironmentally Assisted Cracking) has been developed using the OPS83 programming language. This system is composed of three independent systems, which respectively diagnose the sensitivity of I ) stress corrosion cracking of austenitic stainless steels in a low- or high-concentration chloride solution and/or high-temperature water, II) hydrogen embrittlement of high-strength steels in various aqueous solutions and gaseous environments, and III) hydrogen attack of steel in highly pressurized high-temperature hydrogen gases. The knowledge base consists of production rules, which have certainty factors to represent the uncertainty (contribution) of each rule to environmentally assisted cracking. Applying the developed expert system to the case histories the diagnoses were accurately made. We also proposed the quantitative measure to evaluate the importance of each rule in the diagnosis through the use of the developed expert system.

Anomalous Isotope Effects during Hydrogen Embrittlement of Structural Materials in Electrolytes

The critical stress intensity factors (KHE) in the case of hydrogen embrittlement of high-strength steels, titanium and aluminium alloys in electrolyte solutions in ordinary and deuterium water and in their mixtures have been determined. Two anomalous isotope effects have been discovered: I - the susceptibility of titanium and aluminium alloys to hydrogen embrittlement is higher in deuterium water than in ordinary water; II - the KHE values for steels in mixtures of ordinary and deuterium water are higher than in ordinary water if the potential is increased. The possible reasons for these effects are discussed.

Hydrogen embrittlement of structural materials in solutions of chrome anhydride

Passivating films on metals in solutions of chrome anhydride have highly specific properties~ They protect efficiently structural materials against general corrosion and corrosion cracking (CC) by the mechanism of local dissolution of the metal at the crack tip but do not prevent crack growth in CC by the hydrogen embrittlement (HE) mechanism. The hydrogen embrittlement of titanium and aluminum alloys in these solutions is greatly activated by chloride ions but the hydrogen embrittlement of high-strength steels also takes place at a higher rate in the absence of these ions [I]. The aim of this work was to determine the type of ion which acts as an activator of HE of hi,h-strength steels in pure solutions of chrome anhydride, and also clarify the possibilities of HE in CC of other structural materials in the solutions.

Influence of cations on the hydrogen embrittlement of high-strength steels

Influence of cations on the hydrogen embrittlement of high-strength steels

Role of elongated MnS inclusions in hydrogen embrittlement of high-strength steels

The effect of inclusion orientation and volume fraction on threshold stress intensity K TH and crack-growth rate has been studied as a function of matrix strength and hydrogen activity of the environment by employing a medium carbon hardenable steel having two different sulphur contents (0·04 and 0·15%). The presence of platelike inclusions leads to enhanced crack-growth rate and decreased K TH in the short transverse orientations. In the longitudinal and transverse orientations, inclusions result in the elevation of K TH and reduction of crack-growth rate. The extent of anisotropy in crack-growth rate and K TH caused by a given inclusion dispersion is diminished by an increase in either matrix strength or hydrogen of the environment. It is proposed that the failure for crack growth in hydrogen involves the attainment of a critical tensile stress at a microstructurally significant distance ahead of the crack-tip. The orientation dependence of K TH is attributed to inclusion-induced perturbations of the crack-tip stress field. The results of permeation experiments show that there is no significant directionalty in the diffusivity of hydrogen and it is deduced that anisotropy of crack-growth rate must also be caused primarily by the inclusions affecting the crack-tip stress field.

The applicability of criteria of fracture mechanics for evaluating the hydrogen embrittlement of high-strength steels

The applicability of criteria of fracture mechanics for evaluating the hydrogen embrittlement of high-strength steels

Hydrogen embrittlement of high-strength steel obtained by thermal hardening from rolling heat

Hydrogen embrittlement of high-strength steel obtained by thermal hardening from rolling heat