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[en] The Lead-Lithium cooled Ceramic Breeder - Test Blanket Module (LLCB-TBM) concept has been proposed by India for testing at the International Thermonuclear Experimental Reactor (ITER). Indian Reduced Activation Ferritic-Martensitic Steel (IN RAFMS) has been chosen as a candidate structural material for the Indian LLCB-TBM whereas Lead-17atom% Lithium eutectic (Pb-17Li) will be used as the coolant, neutron multiplier and tritium breeder. An important issue arising from the use of Pb-17Li is the corrosion of containment material and its deleterious effect on the mechanical properties. Ferritic-martensitic (FM) steels; especially the reduced activation varieties; are expected to serve better under fusion reactor environment due to development of lesser swelling and thermal stresses. Nevertheless, the corrosion compatibility of IN RAFMS with Pb-17Li will be an important factor with respect to its qualification for the Indian TBM. In this regard, experiments were conducted in a Rotating Disc Corrosion Test Facility and a Forced circulation loop; where IN RAFMS material in normalized and tempered condition was exposed to molten Pb-17Li for a maximum duration of 5000 h. An IN RAFMS disc was rotated in a Pb-17Li bath under isothermal conditions at 773K in the Rotating Disc test facility whereas rectangular IN RAFMS samples were exposed to flowing Pb-17Li at 773K in the Electromagnetic Pump Driven Lead Lithium Loop (EMPPIL) wherein a gradient of 200 K was maintained between the high and the low temperature regions. Weight losses of exposed samples were measured after the experiments. It was observed that IN RAFMS material corroded at a rate of 1.02 µg/cm"2.h in the rotating disc test facility whereas a corrosion rate of 4.74 µg/cm"2.h was noted for the samples extracted from forced circulation loop. The samples have been further analyzed with the help of Optical Microscopy and Scanning Electron Microscope-Energy Dispersive Spectrometry (SEM-EDS). The results obtained from the above studies will be compared and discussed in the present paper. (author)
[en] The work was devoted to development of the experimental unit for measurement and comparison of tritium permeation rates through bare and protected martensitic steel tubes. Both out-of-pile deuterium gas driven experiments and in-pile tritium permeation experiments were performed. The permeation reduction factor was estimated to be not less than 50 in both series. A few in-pile experiments of 6 h of duration each were performed in a high flux reactor. No degradation of the protection layer was observed for this period
[en] Corrosion damages of welds occur in spite of the fact that the proper base metal and filler metal have been correctly selected, industry codes and standards have been followed and welds have been realized with full weld penetration and have proper shape and contour. In secondary circuit of a Nuclear Power Station there are some components which have dissimilar welds. The principal criteria for selecting a stainless steel usually is resistance to corrosion, and white most consideration is given to the corrosion resistance of the base metal, additional consideration should be given to the weld metal and to the base metal immediately adjacent to the weld zone. Our experiments were performed in chloride environmental on two types of samples: non-welded (410 or W 1.4006 ferritic-martensitic steel and 304L or W 1.4307 austenitic stainless steel) and dissimilar welds (dissimilar metal welds: joints between 410 ferritic-martensitic and 304L austenitic stainless steel). To evaluate corrosion susceptibility of dissimilar welds was used electrochemical method (potentiodynamic method) and optic microscopy (microstructural analysis). The present paper follows the localized corrosion behaviour of dissimilar welds between austenitic stainless steel and ferritic-martensitic steel in solutions containing chloride ions. It was evaluated the corrosion rates of samples (welded and non-welded) by electrochemical methods. (authors)
[en] A clear transition in the tensile ductility behavior has been observed for grain sizes D in the range of 15 μm - 20 μm (1.50 μm ≤ D < 50 μm) in a 22% Mn, 0.6% C (in mass %) TWIP steel. This behavior is a combination of the intrinsic effect of grain size D on strength and work hardening rate of the material, with an extrinsic effect, superficial decarburization and Mn depletion processes occurred during annealing treatments at T ≥ 1000 ºC. In the present work, this extrinsic effect happened in TWIP steel has been studied in depth. GDOES (Glow Discharge Optical Emission Spectrometry) analyses have been carried out in order to study quantitatively the C and Mn concentration profiles. The depth of surface decarburization has been modeled by using Birks-Jackson theory. Two micro-constituents have been observed via Ferritoscope into decarburized volume: α’-martensite and γ-austenite. The ductility of coarse-grained TWIP steel, subjected for high annealing temperatures and long annealing times, declines as a consequence of the formation of α’-martensite and less stable γ-austenite with lower stacking fault energy, SFE, due to the Mn depletion in the decarburized volume.
[es]Se ha observado una clara transición de la ductilidad a tracción con el tamaño de grano D del orden 15 μm - 20 μm (1,50 μm ≤ D < 50 μm) en un acero TWIP, 22% de Mn, 0,6% de C (% en masa). Este comportamiento es una combinación de un efecto intrínseco del tamaño de grano D en la resistencia y el endurecimiento por deformación del material, con un efecto extrínseco, proceso de descarburación superficial y pérdida de Mn ocurrido durante los tratamientos de recocido a T ≥ 1000 ºC. En el presente trabajo se ha estudiado en profundidad este efecto extrínseco sucedido en el acero TWIP. Se han realizado análisis por GDOES (Espectroscopia Óptica de Descarga Luminiscente) para estudiar cuantitativamente los perfiles de concentración de C y Mn. La profundidad de descarburación superficial se ha modelizado usando la teoría de Birks-Jackson. Se ha observado vía ferritoscopio que, en el volumen descarburizado, coexisten dos microconstituyentes: α’-martensita y γ-austenita. La ductilidad del acero TWIP de tamaño de grano grosero, sometido a altas temperaturas y largos tiempos de recocido, disminuye como consecuencia de la formación de α’-martensita y γ-austenita menos estable con menor energía de defectos de apilamiento, EDA, debido a la pérdida de Mn en el volumen descarburizado.
[en] Creep tests on bars made of X 22CrMoV 12 1 for up to 100,000 hours at 500 to 650 C were carried out at the IfW of the TH Darmstadt. A creep equation of the form εf = C.f(σ).g(T).h(t), f(σ) σ.eσ/b, g(T) = e-Q/(T+273), g(T) = e Arrhenius equation, h(t) = tm Bailey equation is derived from the measured creep data for the primary and the start of the secondary creep area. What is new here is the description of the dependence of the stress f(σ), which is derived from the stress relationship of the Norton equation dεf/dt = CN(T, t).σn(σ). With this new equation, it is possible to describe the creep behaviour up to 0.5% creep strain. The time strain limits (from 0.1% strain) determined from the creep tests can be calculated by the new creep equation to the ± 10% of stress. (orig.)
[de]Am IfW der TH-Darmstadt wurden Zeitstandversuche an Stangenmaterial aus X 22 CrMoV 12 1 bis 100 000 Stunden bei 500 bis 650 C durchgefuehrt. Aus den gemessenen Kriechdaten wird hier fuer den Primaer- und den Beginn des Sekundaerkriechbereichs eine Kriechgleichung der Form εf=C.f(σ).g(T).h(t), fσ=σ.eσ/b, g(T)=e-Q/(T+273) Arrhenius-Gleichung, h(t)/tm Bailey-Gleichung, hergeleitet. Neu ist dabei die Beschreibung der Spannungsabhaengigkeit f(σ), die aus der Spannungsabhaengigkeit der Norton-Gleichung dεfdt=CN(T, t).σn(σ) hergeleitet wird. Mit dieser neuen Gleichung ist es moeglich, das Kriechverhalten bis 0,5% Kriechdehnung zu beschreiben. Die aus den Zeitstandversuchen ermittelten Zeitdehngrenzen (ab 0,1% Dehnung) koennen mit der neuen Kriechgleichung auf ±10% in Spannung genau berechnet werden. (orig.)
[en] This work studied the welding metal for a martensitic steel (alloyed to Cr, Mn, Mo, V and W), deposited with a tubular metal-cored wire with gaseous protection of 82%Ar-18%Co2 on a low carbon steel using the semi-automatic welding process. Transverse pieces were cut from the welded coupon for microstructural characterization, measurement of hardness profiles, determination of the chemical composition and wear trials. The microstructural characterization was done using optic and scanning electronic microscopes, X-rays diffraction and energy-dispersive X-ray spectroscopy and Vicker microhardness (1 kg.) was measured. The wear trials (metal-metal) were performed in an Amsler machine under pure flow conditions. Different loads were used and the reference material was a SAE 1020 steel. The temperatures for each case were measured and the weight loss curves were defined as a function of the distance run and of the load. After testing the wear surfaces and the debris were measured. The microstructure of the welded deposit mostly consists of martensite and some retained austenite, with a pattern of dendritic segregation, and a hardness on the surface of 612 HVI. A lineal variation between the weight loss and the load applied was obtained as a response to the wear. The following phenomena were observed: abrasion, plastic deformation, oxidation and adhesion to the wear surfaces, as well as a tempering effect in the condition of the biggest load. The wear mechanisms acting on both surfaces were identified (CW)
[en] Highlights: • Cavity density increased monotonically and swelling decreased monotonically with helium content. • Low helium levels increased cavity density, but did not influence cavity evolution at high damage levels. • High helium levels lowered the critical cavity radius and produced bimodal distributions. • Cavity evolution was suppressed at high helium levels due to helium trapping, or alteration of cavity and dislocation bias. • Dislocations and precipitates did not significantly influence cavity evolution.
[en] Creep rupture tests lasting 100 000 h at temperatures between 500 and 650 C were conducted on X22CrMoV12-1 rods. An equation has been derived from the measured creep data for the primary and the beginning of the secondary creep range. A new element in the equation is the description for the dependency on stress f(σ) which was obtained from the stress dependency in the Norton equation. The new equation allows the description of the creep behaviour up to a strain of 0.5 %. Using the equation, the corresponding stress can be calculated to an accuracy of ±10 % from the strain limits determined in relation to time during creep rupture tests (above 0.1 % strain). (orig.)
[en] Low-activated F82H-mod. steel plate material was made available by the Japanese side to the European laboratories, where various tests are performed within the framework of the Fusion Technology Research Program. The activities of the FZK-IMF I focused among others on the investigation of the creep and creep-rupture strength behavior. The tests were performed on three plates in the reference state (as received = 1040 38'+750 1 h) at temperatures of 450-700 C for a period of up to 30000 h. Furthermore, the aging behavior following stabilization annealing (550/600 -5000 h) and the influence of reduced hardening temperatures (950 or 1000 C) were examined. On the basis of the experimental data and in accordance with the design criteria for 400-650 C/20000 h, minimum values could be indicated for the 1% time yield limit and the creep-rupture strength. In addition, specimens were tested at 875 C hardening temperature and tests were performed with a preliminary temperature transient to 875 C, during which a two-phase structure of martensite+ferrite was formed. The associated decrease in strength could be quantified. (orig.)
[en] The 12% Cr steels are frequently used in German power plants for tubings, pipes, rotors, and blades. The maximum operating temperature is limited by their creep strength properties to about 5500C. There are applications at even higher temperatures. Sufficient materials toughness is required for the base metal and weld metal to withstand sudden load changes. This is of special interest for use in nuclear power plants. Under operating conditions at elevated temperatures microstructural changes occur which greatly influence the toughness properties of both base metal and weld metal. This paper presents the results of ageing treatments at 5550C, carried out with a 12% Cr steel (DIN X20 CrMoV 12 1) specifically optimized for toughness. The decrease in toughness is already evident at ageing times as low as 1000 h for conventional and optimized material. This drop in toughness is tentatively explained by differences in grain sizes and carbide content (M23C6 carbides). Detailed investigations indicate that additional carbide precipitation may significantly contribute to the decrease in toughness. (orig.)