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[en] Hydrogen embrittlement is a complex phenomenon, involving several length- and timescales, that affects a large class of metals. It can significantly reduce the ductility and load-bearing capacity and cause cracking and catastrophic brittle failures at stresses below the yield stress of susceptible materials. Despite a large research effort in attempting to understand the mechanisms of failure and in developing potential mitigating solutions, hydrogen embrittlement mechanisms are still not completely understood. There are controversial opinions in the literature regarding the underlying mechanisms and related experimental evidence supporting each of these theories. The aim of this paper is to provide a detailed review up to the current state of the art on the effect of hydrogen on the degradation of metals, with a particular focus on steels. Here, we describe the effect of hydrogen in steels from the atomistic to the continuum scale by reporting theoretical evidence supported by quantum calculation and modern experimental characterisation methods, macroscopic effects that influence the mechanical properties of steels and established damaging mechanisms for the embrittlement of steels. Furthermore, we give an insight into current approaches and new mitigation strategies used to design new steels resistant to hydrogen embrittlement.
[en] Recently, alternative and novel energy resources have been developed for use in the future because of the current environmental problems and exhaustion of fossil energy resources. Hydrogen energy has many merits, such as its environmental friendliness, easy storage, and easy production, but it also has disadvantages, in that it is highly combustible and explosive. In this study, a test procedure using a simple SP test under highly pressurized hydrogen gas conditions was established. In order to evaluate its applicability, SP tests were carried out using a stainless steel (SUS316L) sample under atmospheric, pressurized helium, and pressurized hydrogen gas conditions. The results under the pressurized hydrogen gas condition showed fissuring and produced a reduction of the elongation in the plastic instability region due to hydrogen embrittlement, showing the effectiveness of the current in-situ SP test
[en] Severe embrittlement can be produced in many metals by small amounts of hydrogen. The interactions of hydrogen with lattice imperfections are important and often dominant in determining the influence of this impurity on the properties of solids. The interaction between four-hydrogen atoms and a BCC Fe structure having a vacancy has been studied using a cluster model and a semiempirical method. For a study of sequential absorption, the hydrogen atoms were positioned in their energy minima configurations, near to the tetrahedral sites neighbouring the vacancy. VH2 and VH3 complexes are energetically the most stables in BCC Fe. The studies about the stability of the hydrogen agglomeration gave as a result that the accumulation is unfavourable in complex vacancy-hydrogen with more than three atoms of hydrogen. (authors)
[en] Hydrogen has ideal characteristics as an energy carrier. Hydrogen can be used as a clean fuel in a variety of energy end-use sectors including the conversion to electricity. After combustion, it produces only water. Therefore, the concept of hydrogen energy system has attracted much interest worldwide. But hydrogen has a defect that the explosion risk is high to an inflammable gas of a colorless, tasteless and odorless. Therefore, to use the hydrogen to the source of energy, hydrogen accident sequences and causes analysis must be needed. For this, hazard types occurring in hydrogen facilities have been considered through the case of domestic and foreign hydrogen accident in this study and hazard types to be considered are ignition, leaks, hydrogen dispersion, fire an explosion, storage vessel failure, vent and exhaust system, purging, condensation of air, hydrogen embrittlement, physiological hazard, and collisions during transportation
[en] Main methods of zirconium alloy powder synthesis have been reviewed. Powder applications for additive manufacturing were analyzed. Advantages and drawbacks of zirconium powder production and usage have been shown. Hydrogenation/dehydrogenation method was offered for zirconium powder production.
[en] The effect of hydrogen charging on dislocation multiplication in super duplex stainless steel was investigated. Steel samples were pre-strained and charged with hydrogen for 10 days. Dislocation density was then measured using neutron diffraction. It is found that dislocation density multiplies by about one order of magnitude in samples with less than 5% pre-strain, but remains the same level in samples with pre-strain level of 10% and above.
[en] Hydrogen may play a role in nuclear applications when it is present as the gas necessary for the specific process (fusion reactors, accelerators), or as a chemical compound, for example as cooling water or as moderator (fission reactors), or when it is formed by nuclear processes in the surrounding structures, as for example it happens in a fusion reactor due to the interaction of the high energy neutrons with other materials. Some problems arise when hydrogen or its isotopes are forced or penetrate into solids and remain trapped inside the lattice. Depending on the material and on the temperature, the hydrogen can remain in solution, can form hydrogen bubbles or brittle phases, and can be trapped by other lattice defects. In most of these cases the mechanical properties of the structures will be reduced. In addition it is necessary to take care, that the hydrogen can not form explosive mixtures, and, if the heavy isotope tritium is used, that it can not be released in an uncontrolled manner to environment
[en] The phenomena of steel brittleness from hydrogen is a well known problem in materials science, but its explanation at the microscopic level is far from being fully understood. This work studies the energetic of C location and of various hydrogen atoms in the void of the divacancy, using semi-empirical tight interlocking calculations. The defect is simulated by a two dimensional slab with 124 atoms of Fe in the unitary cell. Density graphs of projected states and of crystalline overlapping population were made. The C is located in the central part of the vacancy running towards the voids of the Fe. The H shows no association with the C and it fastens onto bridge positions shared between two Fe atoms. When the C is present, the total energy of the slab drops and the same occurs when additional H atoms are incorporated, so that the vacancy acts as a trap for these interstitials. The analysis of the electronic structure reveals s-s interactions between Fe and C and H as the majority for the connection. The d orbitals are responsible for the spatial location of the impurities. The overlapping population of the Fe-Fe links decrease proportionally to the weakening of the network by up to 60%. Our results do not confirm the formation of C-H species in the divacancy. The interaction between interstitials does not appear to be important and the Fe-C and Fe-H interaction prevails (CW)
[en] The original paper contains a mistake in the acronym AIDE. The AIDE acronym mistake occurs in the title of the section heading and in the following text on p. 6276, and in the text in the section “Discussion and outlook on the HE mechanisms” on p. 6277.
[en] In this paper, after a review of the accidents/incidents, are described the different interactions between hydrogen gas and the most commonly used materials including the influence of 'internal' and 'external' hydrogen, the phenomena occurring in all ranges of temperatures and pressures and Hydrogen Embrittlement (HE) created by gaseous hydrogen. The principle of all the test methods used to investigate this phenomenon are presented and discussed. The advantages and disadvantages of each method will be explained. The paper also covers the influence of all the parameters related to HE including the ones related to the material itself, the ones related to the design and manufacture of the equipment and the ones related to the hydrogen itself (pressure, temperature, purity, etc.). A review of the accidents/incidents due to HE is also presented and finally recommendations to avoid repetition of such accidents/incidents are proposed. (authors)