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[en] In D-T fusion plants, the management of all hydrogen isotopes is implicit; assuming that coolant temperatures will be near 300 degrees C and that no major relaxation in tritium effluent occurs. Regardless of the design and configuration of these plants, it is anticipated that hydrogen barriers will be an integral part of the tritium management system. Hydrogen barriers are necessary to kinetically limit the achievement of thermodynamic or isotopic equilibrium through a hermetic boundary. Uncontrolled tritium or hydrogen transport in fusion plants can lead to tritium inventory buildup in the plant, tritium contaminated effluents, high tritium concentrations in work areas, hydrogen embrittlement of metals, and more difficult tritium processing. Hydrogen degradation of the mechanical properties of structural alloys is an issue which can be improved and hampered by effective barriers. Tritium/hydrogen barriers have evolved in a variety of applications for the past several decades. In addition to achieving high permeation reduction factors for the structural material they are applied to, tritium barriers are required to survive the same conditions as the base metal, i.e. corrosion, irradiation, mechanical stresses, etc. To permeate a barrier coated metal, a hydrogen isotope must be absorbed on the surface, diffuse through the base metal and undergo desorption at the opposite surface. Simple oxidation had provided about one order of magnitude reduction in hydrogen permeation for most fusion structural materials. Varying success has been achieved with heterogeneous carbide, nitride and oxide coatings applied to metals. Far greater success has been reported for intermetallic coatings, such as aluminides, which generate high permeation reduction factors (up to 10000) and yet possess reasonable ductility. This paper provides a review of the available literature on both developmental and experimental tritium/hydrogen barrier coatings
[en] This paper analyzes the process of progressive damage produced by mechanical origins (plasticity) and environmental causes (hydrogen embrittlement) in 316L austenitic stainless steel for the first wall of fusion reactors. Results of the analysis show that the micromechanical damage created by hydrogen is concentrated in an external circumferential ring with the same center as the cross sectional area of the notched samples. The microscopical appearance of this embrittled zone or damaged area is very rough and irregular at the microscale, with evidence of microcracking or secondary cracking, in contrast with the smooth surface (at the microscale) created by microvoid coalescence (dimpled fracture) in the inner core which is not embrittled by hydrogen and thus fails by mechanical reasons. The depth of the hydrogen damaged zone is quantified by fractographic methods and related to the test variables. (orig.)
[en] The cathodic protection method is being widely used marine structural steel, however a high tensile steel like RE 36 steel for marine structural steel is easy to get hydrogen embrittlement due to over protection during cathodic protection as well as preferential corrosion of HAZ(Heating Affected Zone) part. In this paper, corrosion resistance and mechanical properties such as elongation and hydrogen embrittlement were investigated with not only in terms of electrochemical view but also SSRT(Slow Strain Rate Test) method with applied constant cathodic potential, analysis of SEM fractography in case of both As-welded and PWHT(Post-Weld Heat Treatment) of 550 .deg. C. The best effect for corrosion resistance was apparently indicated at PWHT of 550 .deg. C and elongation was increased with PWHT of 550 .deg. C than that of As-welded condition. On the other hand. Elongation was decreased with applied potential shifting to low potential direction which may be caused by hydrogen embrittlement, however the susceptibility of hydrogen embrittlement was decreased with PWHT of 550 .deg. C than that of As-welded condition and Q.C(quasi cleavage) fracture mode was also observed significantly according to increasing of susceptibility of hydrogen embrittlement. Eventually it is suggested that an optimum cathodic protection potential range not causing hydrogen embrittlement is from -770 mV(SCE) to-850mV(SCE) in As-welded condition while is from-770 mV(SCE) to -875 mV(SCE) in PWHT of 550 .deg. C
[en] The effects of electrochemically introduced hydrogen on the room temperature mechanical properties of two β titanium alloys, TIMETAL 15-3 (Ti-15V-3Cr-3AI-3Sn, wt%) and TIMETAL 21S (Ti-15Mo-3Nb-3Al, wt%) are compared. Solution annealed, peak aged (538 C, 8h), and duplex aged (440 C, 20h, 538 C, 1/2h) conditions are investigated. Bridgman notched tensile bars are employed to quantify the degree of embrittlement both by reduction in the maximum longitudinal stress developed at the centerline of the notch and the average effective plastic strain across the notch diameter at maximum load. Fracture paths are correlated with the slip behavior observed in solution annealed material. Possible hydriding of the α and β phases is investigated through x-ray diffraction. Results show that TIMETAL 21S is more susceptible to hydrogen embrittlement than TIMETAL 15-3 as evidenced by reductions in the longitudinal stress, plastic strain, and changes in fracture mode at hydrogen concentrations above 1,000 wt. ppm. Possible hydriding of a large volume fraction of the α or β phases was not observed over the range of hydrogen concentrations investigated. The increased susceptibility of TIMETAL 21S to hydrogen embrittlement is attributed to a high temperature, long time, solution treatment which removed heterogeneous nucleation sites from the grain interiors. Subsequent aging occurs preferentially on β grain boundaries and lastly in the grain interiors, resulting in fine intragranular precipitates. These fine α plates are readily sheared and promote planar slip. In contrast, a lower temperature, shorter duration solution treatment for TIMETAL 15-3, results in a material with more homogeneous, larger α precipitates, which, in turn, promote wavy slip. Results indicate that persistent planar slip exacerbates both hydrogen embrittlement and aqueous environmentally assisted cracking in metastable β titanium alloys
[en] Environmental effects on titanium aluminide alloys are potentially of great importance for engineering applications of these materials, although little has been published to date on such effects. The primary emphasis in this paper is on hydrogen effects, with a brief reference to oxygen effects. Hydrogen is readily absorbed at elevated temperature into all the titanium aluminide compositions studied to date, in amounts as large as 10 at.%, and on cooling virtually all this hydrogen is precipitated as a hydride phase or phases. The presence of these precipitated hydride plates affects mechanical properties in ways similar to what is observed in other hydride forming materials, although effects per unit volume of hydride are not particularly severe in the titanium aluminides. Microstructure, and thus thermal and mechanical history, plays a major role in controlling the severity of hydrogen effects
[en] Ti-25Al, Ti-25Al-10Nb-2V, and Ti-25Al-10Nb-3V-1Mo (at.%) α2-based alloys, and Ti-48Al and Ti-52Al γ-based alloys were exposed to gaseous hydrogen at elevated temperatures. A novel ternary hydride was observed in Ti-25Al and Ti-25Al-10Nb-3V-1Mo, identified as Ti3AlH. A highly faulted ternary hydride was seen in two phase α2 + γTi-48Al which did not have the crystal structure or chemistry of any known Ti- or Ti-Al-hydride. Very fine, oriented, needle-shaped hydrides were observed in singe-phase γ Ti-52Al
[en] The contributions of this congress address challenges, strategies and developed solutions to deal with the use of materials under extreme conditions with presentations of the elaboration of original materials with specific strengths, of the development of mechanisms aimed at delaying the material failure, of the design of original devices to test these materials, and of the development of original models and simulations. In the large field of energy, addressed topics concern the degradation of ceramic matrix C/SiC composites, crystallisation of zircon in electro-melt refractory materials, high temperature oxidation of compounds based on ZrB2-SiC fibre, behaviour and damage of C/C composites, fabrication and characterisation of new hexagonal structures in ceramic matrix composite for nuclear application, new fibrous architectures and densification for SiC/SiC components of 4. generation reactors, effect of helium in metallic materials for new generation reactors, modelling and prediction of radiative properties of semi-transparent ceramic materials, damage under electronic irradiation of silicate-based phases of the anhydrous concrete, influence of fission gases on the mechanical condition of irradiated nuclear fuel, microstructural study of UO2 implanted with ions, and so on
[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] In this paper the strain rate sensitivities of 93% W and 70% W heavy metal alloys are characterized in the hydrogen-charged and vacuum outgassed conditions. In outgassed material, strength increases as ductility decreases with increased strain rate; however, for hydrogen-charged material, ductility as well as characteristically ductile to brittle as strain rate increases. An integrated model is presented that illustrates the change in fracture behavior with strain rate for ductile, hydrogen-embrittled, and impurity-segregation embrittled material
[en] Injecting hydrogen in the natural gas grid poses a number of problems. Does hydrogen hold the key to the great energy transition to come? France and other countries believe this to be the case, and have chosen to invest heavily in the sector. Such spending will be needed to solve the many issues raised by this energy carrier. One such issue is containers, since hydrogen tends to damage metallic materials. At Mines Saint-etienne, Frederic Christien and his teams are trying to answer these questions.
[fr]L'injection d'hydrogene dans le reseau de gaz naturel n'est pas sans poser certains problemes. L'hydrogene represente-t-il la cle de la future grande transition energetique? C'est la conviction de la France, ainsi que d'autres pays qui ont choisi d'investir massivement dans cette filiere. Un budget qui ne sera pas de trop pour resoudre les nombreux problemes souleves par ce vecteur energetique. Parmi eux figure la question de son conditionnement, l'hydrogene ayant tendance a endommager les materiaux metalliques. a Mines Saint-etienne, Frederic Christien et ses equipes tentent d'y apporter des elements de reponse.