Research

18 pages, 6812 KiB

Open AccessArticle

Determination of Hydrogen Transport Behaviour in Boron-Manganese Steels Using Different Methods and Boundary Conditions

by Matthias Kuhlmann, Niels Mitzschke and Sven Jüttner

Metals 2019, 9(9), 1007; https://doi.org/10.3390/met9091007 - 12 Sep 2019

Cited by 5 | Viewed by 3488

Within the framework of the project "ELOBEV" (research of electrolytic coating systems for joining elements made of high-strength materials) funded by the Federal Ministry of Education and Research, a test methodology for the assessment of the danger of hydrogen-assisted and liquid metal-induced cracking [...] Read more.

Within the framework of the project "ELOBEV" (research of electrolytic coating systems for joining elements made of high-strength materials) funded by the Federal Ministry of Education and Research, a test methodology for the assessment of the danger of hydrogen-assisted and liquid metal-induced cracking for auxiliary joining elements is being developed. One working point of the project is the determination of the hydrogen transport behaviour in high-strength boron-manganese steels and their coating concepts. Permeation measurements under different boundary conditions are used to characterize the hydrogen transport in 22MnB5 and 37MnB4. The results are validated by thermal desorption analyses with a constant heating rate and an isothermal temperature control. Several methods for the determination of the diffusion velocity are investigated and the determined values are compared with each other. Full article

(This article belongs to the Special Issue Hydrogen Embrittlement of Metallic Materials: Past, Present and Future)

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12 pages, 4383 KiB

Open AccessArticle

Investigation of Mechanical Tests for Hydrogen Embrittlement in Automotive PHS Steels

by Renzo Valentini, Michele Maria Tedesco, Serena Corsinovi, Linda Bacchi and Michele Villa

Metals 2019, 9(9), 934; https://doi.org/10.3390/met9090934 - 27 Aug 2019

Cited by 16 | Viewed by 4289

Abstract

The problem of hydrogen embrittlement in ultra-high-strength steels is well known. In this study, slow strain rate, four-point bending, and permeation tests were performed with the aim of characterizing innovative materials with an ultimate tensile strength higher than 1000 MPa. Hydrogen uptake, in [...] Read more.

The problem of hydrogen embrittlement in ultra-high-strength steels is well known. In this study, slow strain rate, four-point bending, and permeation tests were performed with the aim of characterizing innovative materials with an ultimate tensile strength higher than 1000 MPa. Hydrogen uptake, in the case of automotive components, can take place in many phases of the manufacturing process: during hot stamping, due to the presence of moisture in the furnace atmosphere, high-temperature dissociation giving rise to atomic hydrogen, or also during electrochemical treatments such as cataphoresis. Moreover, possible corrosive phenomena could be a source of hydrogen during an automobile’s life. This series of tests was performed here in order to characterize two press-hardened steels (PHS)—USIBOR 1500^® and USIBOR 2000^®—to establish a correlation between ultimate mechanical properties and critical hydrogen concentration. Full article

(This article belongs to the Special Issue Hydrogen Embrittlement of Metallic Materials: Past, Present and Future)

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18 pages, 7441 KiB

Open AccessArticle

The Effects of Electrochemical Hydrogen Charging on Room-Temperature Tensile Properties of T92/TP316H Dissimilar Weldments in Quenched-and-Tempered and Thermally-Aged Conditions

by Peter Ševc, Ladislav Falat, Lucia Čiripová, Miroslav Džupon and Marek Vojtko

Metals 2019, 9(8), 864; https://doi.org/10.3390/met9080864 - 08 Aug 2019

Cited by 6 | Viewed by 3013

Abstract

The influence of isothermal aging at 620 °C in combination with subsequent electrochemical hydrogen charging at room-temperature was studied on quenched-and-tempered T92/TP316H martensitic/austenitic weldments in terms of their room-temperature tensile properties and fracture behavior. Hydrogen charging of the weldments did not significantly affect [...] Read more.

The influence of isothermal aging at 620 °C in combination with subsequent electrochemical hydrogen charging at room-temperature was studied on quenched-and-tempered T92/TP316H martensitic/austenitic weldments in terms of their room-temperature tensile properties and fracture behavior. Hydrogen charging of the weldments did not significantly affect their strength properties; however, it resulted in considerable deterioration of their plastic properties along with significant impact on their fracture characteristics and failure localization. The hydrogen embrittlement plays a dominant role in degradation of the plastic properties of the weldments already in their initial material state, i.e., before thermal aging. After thermal aging and subsequent hydrogen charging, mutual superposition of thermal and hydrogen embrittlement phenomena had led to clearly observable effects on the welds deformation and fracture processes. The measure of hydrogen embrittlement was clearly lowered for thermally aged material state, since the contribution of thermal embrittlement to overall degradation of the weldments has dominated. The majority of failures of the weldments after hydrogen charging occurred in the vicinity of T92 BM/Ni weld metal (WM) fusion zone; mostly along the Type-II boundary in Ni-based weld metal. Thus, regardless of aging exposure, the most critical failure regions of the investigated weldments after hydrogen charging and tensile straining at room temperature are the T92 BM/Ni WM fusion boundary and Type-II boundary acting like preferential microstructural sites for hydrogen embrittling effects accumulation. Full article

(This article belongs to the Special Issue Hydrogen Embrittlement of Metallic Materials: Past, Present and Future)

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14 pages, 4790 KiB

Open AccessArticle

Charpy Impact Properties of Hydrogen-Exposed 316L Stainless Steel at Ambient and Cryogenic Temperatures

by Le Thanh Hung Nguyen, Jae-Sik Hwang, Myung-Sung Kim, Jeong-Hyeon Kim, Seul-Kee Kim and Jae-Myung Lee

Metals 2019, 9(6), 625; https://doi.org/10.3390/met9060625 - 29 May 2019

Cited by 17 | Viewed by 8795

Abstract

316L stainless steel is a promising material candidate for a hydrogen containment system. However, when in contact with hydrogen, the material could be degraded by hydrogen embrittlement (HE). Moreover, the mechanism and the effect of HE on 316L stainless steel have not been [...] Read more.

316L stainless steel is a promising material candidate for a hydrogen containment system. However, when in contact with hydrogen, the material could be degraded by hydrogen embrittlement (HE). Moreover, the mechanism and the effect of HE on 316L stainless steel have not been clearly studied. This study investigated the effect of hydrogen exposure on the impact toughness of 316L stainless steel to understand the relation between hydrogen charging time and fracture toughness at ambient and cryogenic temperatures. In this study, 316L stainless steel specimens were exposed to hydrogen in different durations. Charpy V-notch (CVN) impact tests were conducted at ambient and low temperatures to study the effect of HE on the impact properties and fracture toughness of 316L stainless steel under the tested temperatures. Hydrogen analysis and scanning electron microscopy (SEM) were conducted to find the effect of charging time on the hydrogen concentration and surface morphology, respectively. The result indicated that exposure to hydrogen decreased the absorbed energy and ductility of 316L stainless steel at all tested temperatures but not much difference was found among the pre-charging times. Another academic insight is that low temperatures diminished the absorbed energy by lowering the ductility of 316L stainless steel. Full article

(This article belongs to the Special Issue Hydrogen Embrittlement of Metallic Materials: Past, Present and Future)

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12 pages, 5046 KiB

Open AccessArticle

The Role of Hydrogen in Hydrogen Embrittlement of Metals: The Case of Stainless Steel

by Young Suk Kim, Sung Soo Kim and Byung Hak Choe

Metals 2019, 9(4), 406; https://doi.org/10.3390/met9040406 - 03 Apr 2019

Cited by 14 | Viewed by 6905

Abstract

Hydrogen embrittlement (HE) of metals has remained a mystery in materials science for more than a century. To try to clarify this mystery, tensile tests were conducted at room temperature (RT) on a 316 stainless steel (SS) in air and hydrogen of 70 [...] Read more.

Hydrogen embrittlement (HE) of metals has remained a mystery in materials science for more than a century. To try to clarify this mystery, tensile tests were conducted at room temperature (RT) on a 316 stainless steel (SS) in air and hydrogen of 70 MPa. With an aim to directly observe the effect of hydrogen on ordering of 316 SS during deformation, electron diffraction patterns and images were obtained from thin foils made by a focused ion beam from the fracture surfaces of the tensile specimens. To prove lattice contraction by ordering, a 40% CW 316 SS specimen was thermally aged at 400 °C to incur ordering and its lattice contraction by ordering was determined using neutron diffraction by measuring its lattice parameters before and after aging. We demonstrate that atomic ordering is promoted by hydrogen, leading to formation of short-range order and a high number of planar dislocations in the 316 SS, and causing its anisotropic lattice contraction. Hence, hydrogen embrittlement of metals is controlled by hydrogen-enhanced ordering during RT deformation in hydrogen. Hydrogen-enhanced ordering will cause the ordered metals to be more resistant to HE than the disordered ones, which is evidenced by the previous observations where furnace-cooled metals with order are more resistant to HE than water-quenched or cold worked metals with disorder. This finding strongly supports our proposal that strain-induced martensite is a disordered phase. Full article

(This article belongs to the Special Issue Hydrogen Embrittlement of Metallic Materials: Past, Present and Future)

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14 pages, 3174 KiB

Open AccessArticle

Hydrogen Effect on the Cyclic Behavior of a Superelastic NiTi Archwire

by Rihem Sarraj, Amir Kessentini, Tarek Hassine, Ali Algahtani and Fehmi Gamaoun

Metals 2019, 9(3), 316; https://doi.org/10.3390/met9030316 - 11 Mar 2019

Cited by 5 | Viewed by 3324

Abstract

In this work, we are interested in examining the strain rate effect on the mechanical behavior of Ni–Ti superelastic wires after hydrogen charging and ageing for 24 h. Specimens underwent 50 cycles of loading-unloading, reaching an imposed deformation of 7.6%. During loading, strain [...] Read more.

In this work, we are interested in examining the strain rate effect on the mechanical behavior of Ni–Ti superelastic wires after hydrogen charging and ageing for 24 h. Specimens underwent 50 cycles of loading-unloading, reaching an imposed deformation of 7.6%. During loading, strain rates from 10⁻⁴ s⁻¹ to 10⁻² s⁻¹ were achieved. With a strain rate of 10⁻² s⁻¹, the specimens were charged by hydrogen for 6 h and aged for one day showed a superelastic behavior marked by an increase in the residual deformation as a function of the number of cycles. In contrast, after a few number of cycles with a strain rate of 10⁻⁴ s⁻¹, the Ni-Ti alloy archwire specimens fractured in a brittle manner during the martensite transformation stage. The thermal desorption analysis showed that, for immersed specimens, the desorption peak of hydrogen appeared at 320 °C. However, after annealing the charged specimens by hydrogen at 400 °C for 1 h, an embrittlement took place at the last cycles for the lower strain rates of 10⁻⁴ s⁻¹. The present study suggests that the embrittlement can be due to the development of an internal stress in the subsurface of the parent phase during hydrogen charging and due to the creation of cracks and local zones of plasticity after desorption. Full article

(This article belongs to the Special Issue Hydrogen Embrittlement of Metallic Materials: Past, Present and Future)

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15 pages, 2388 KiB

Open AccessArticle

Ab Initio Study of the Combined Effects of Alloying Elements and H on Grain Boundary Cohesion in Ferritic Steels

by Aparna P. A. Subramanyam, Abril Azócar Guzmán, Smobin Vincent, Alexander Hartmaier and Rebecca Janisch

Metals 2019, 9(3), 291; https://doi.org/10.3390/met9030291 - 05 Mar 2019

Cited by 14 | Viewed by 4546

Abstract

Hydrogen enhanced decohesion is expected to play a major role in ferritic steels, especially at grain boundaries. Here, we address the effects of some common alloying elements C, V, Cr, and Mn on the H segregation behaviour and the decohesion mechanism at a [...] Read more.

Hydrogen enhanced decohesion is expected to play a major role in ferritic steels, especially at grain boundaries. Here, we address the effects of some common alloying elements C, V, Cr, and Mn on the H segregation behaviour and the decohesion mechanism at a

Σ 5 (310) [001]

{36.9}^{\circ}

grain boundary in bcc Fe using spin polarized density functional theory calculations. We find that V, Cr, and Mn enhance grain boundary cohesion. Furthermore, all elements have an influence on the segregation energies of the interstitial elements as well as on these elements’ impact on grain boundary cohesion. V slightly promotes segregation of the cohesion enhancing element C. However, none of the elements increase the cohesion enhancing effect of C and reduce the detrimental effect of H on interfacial cohesion at the same time. At an interface which is co-segregated with C, H, and a substitutional element, C and H show only weak interaction, and the highest work of separation is obtained when the substitute is Mn. Full article

(This article belongs to the Special Issue Hydrogen Embrittlement of Metallic Materials: Past, Present and Future)

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18 pages, 6277 KiB

Open AccessArticle

Formation Criterion of Hydrogen-Induced Cracking in Steel Based on Fracture Mechanics

by Lei Fu and Hongyuan Fang

Metals 2018, 8(11), 940; https://doi.org/10.3390/met8110940 - 13 Nov 2018

Cited by 12 | Viewed by 5108

Abstract

A new criterion for hydrogen-induced cracking (HIC) that includes both the embrittlement effect and the loading effect of hydrogen was obtained theoretically. The surface cohesive energy and plastic deformation energy are reduced by hydrogen atoms at the interface; thus, the fracture toughness is [...] Read more.

A new criterion for hydrogen-induced cracking (HIC) that includes both the embrittlement effect and the loading effect of hydrogen was obtained theoretically. The surface cohesive energy and plastic deformation energy are reduced by hydrogen atoms at the interface; thus, the fracture toughness is reduced according to fracture mechanics theory. Both the pressure effect and the embrittlement effect mitigate the critical condition required for crack instability extension. During the crack instability expansion, the hydrogen in the material can be divided into two categories: hydrogen atoms surrounding the crack and hydrogen molecules in the crack cavity. The loading effect of hydrogen was verified by experiments, and the characterization methods for the stress intensity factor under hydrogen pressure in a linear elastic model and an elastoplastic model were analyzed using the finite-element simulation method. The hydrogen pressure due to the aggregation of hydrogen molecules inside the crack cavity regularly contributed to the stress intensity factor. The embrittlement of hydrogen was verified by electrolytic charging hydrogen experiments. According to the change in the atomic distribution during crack propagation in a molecular dynamics simulation, the transition from ductile to brittle fracture and the reduction in the fracture toughness were due to the formation of crack tip dislocation regions suppressed by hydrogen. The HIC formation mechanism is both the driving force of crack propagation due to the hydrogen gas pressure and the resisting force reduced by hydrogen atoms. Full article

(This article belongs to the Special Issue Hydrogen Embrittlement of Metallic Materials: Past, Present and Future)

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11 pages, 2054 KiB

Open AccessArticle

Hydrogen Embrittlement Susceptibility of R4 and R5 High-Strength Mooring Steels in Cold and Warm Seawater

by Garikoitz Artola, Alberto Arredondo, Ana Isabel Fernández-Calvo and Javier Aldazabal

Metals 2018, 8(9), 700; https://doi.org/10.3390/met8090700 - 06 Sep 2018

Cited by 9 | Viewed by 4177

Abstract

Hydrogen embrittlement susceptibility ratios calculated from slow strain rate tensile tests have been employed to study the response of three high-strength mooring steels in cold and warm synthetic seawater. The selected nominal testing temperatures have been 3 °C and 23 °C in order [...] Read more.

Hydrogen embrittlement susceptibility ratios calculated from slow strain rate tensile tests have been employed to study the response of three high-strength mooring steels in cold and warm synthetic seawater. The selected nominal testing temperatures have been 3 °C and 23 °C in order to resemble sea sites of offshore platform installation interest, such as the North Sea and the Gulf of Mexico, respectively. Three scenarios have been studied for each temperature: free corrosion, cathodic protection and overprotection. An improvement on the hydrogen embrittlement tendency of the steels has been observed when working in cold conditions. This provides a new insight on the relevance of the seawater temperature as a characteristic to be taken into account for mooring line design in terms of hydrogen embrittlement assessment. Full article

(This article belongs to the Special Issue Hydrogen Embrittlement of Metallic Materials: Past, Present and Future)

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