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The microstructure of a Ren&eacute, 108 Ni-based superalloy was systematically investigated by X-ray diffraction, light microscopy, energy-dispersive X-ray spectroscopy, and electron microscopy techniques. The material was investment cast in a vacuum and then solution treated (1200 &deg, C-2h) and aged (900 &deg, C-8h). The &gamma, matrix is mainly strengthened by the ordered L12 &gamma, &prime, phase, with the mean &gamma, /&gamma, misfit, &delta, +0.6%. The typical dendritic microstructure with considerable microsegregation of the alloying elements is revealed. Dendritic regions consist of secondary and tertiary &gamma, precipitates. At the interface of the matrix with secondary &gamma, precipitates, nano M5B3 borides are present. In the interdendritic spaces additionally primary &gamma, precipitates, MC and nano M23C6 carbides were detected. The &gamma, precipitates are enriched in Al, Ta, Ti, and Hf, while channels of the matrix in Cr and Co. The highest summary concentration of &gamma, formers occurs in coarse &gamma, surrounding MC carbides. Borides M5B3 contain mostly W, Cr and Mo. All of MC carbides are enriched strongly in Hf and Ta, with the concentration relationship between these and other strong carbide formers depending on the precipitate&rsquo, s morphology. The nano M23C6 carbides enriched in Cr have been formed as a consequence of phase transformation MC + &gamma, &rarr, M23C6 + &gamma, during the ageing treatment.

In situ X-ray diffraction and transmission electron microscopy has been used to investigate Ren&eacute, 108 Ni-based superalloy after short-term annealing at high-homologous temperatures. Current work is focused on characterisation of &gamma, ' precipitates, their volume fraction, evolution of the lattice parameter of &gamma, and &gamma, ' phases and misfit parameter of &gamma, ' in the matrix. Material in the initial condition is characterised by a high-volume fraction (over 63%) of &gamma, ' precipitates. Irregular distribution of alloying elements was observed. Matrix channels were strongly enriched in Cr, Co, W and Mo, whereas precipitates contain large amount of Al, Ti, Ta and Hf. Exposure to high-homologous temperatures in the range 1100&ndash, 1250 &deg, C led to the dissolution of the precipitates, which influenced the change of lattice parameter of both &gamma, ' phases. The lattice parameter of the matrix continuously grew during holding at high temperatures, which had a dominant influence on the more negative misfit coefficient.

Microstructural changes in the age-hardenable Fe-28wt.%Mn-9wt.%Al-1wt.%C steel during ageing at 550°C for various times have been investigated by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The steel was produced in an induction furnace and the ingot, after homogenization at 1150°C for 3 hours under a protective argon atmosphere, was hot-rolled and subsequently cold-rolled up to 23% reduction. The sheet was then aged at 550°C for various times in an argon atmosphere and cooled in air. XRD analysis and TEM observations revealed a modulated structure and superlattice reflections produced by spinodal decomposition, which occurred during ageing at 550°C. Theexistence of satellites suggests that either (Fe, Mn)3AlCx carbides were formed within the austenite matrix by spinodal decomposition during cooling or chemical fluctuactions occurred between the (Fe, Mn)3AlCx carbides and the austenitic matrix.

Przedmiotem badań były złącza spawane ze stopu niklu umacnianego roztworowo o nazwie handlowej Hastelloy X. Proces spawania przeprowadzono metodą GTAW (z ang. Gas Tungsten Arc Welding) na materiale w stanie dostawy oraz po eksploatacji tj. pochodzącym z turbiny gazowej. W celu porównania zmian mikrostrukturalnych i własności wykonano badania za pomocą mikroskopii świetlnej, skaningowej oraz pomiary mikrotwardości. Dodatkowo przeprowadzono badania za pomocą transmisyjnej mikroskopii elektronowej (TEM) w obszarze materiału rodzimego po eksploatacji. Wykonane badania TEM były podstawą do stwierdzenia, iż temperatura eksploatacji wpłynęła jedynie na zwiększenie ilości i średnicy wydzieleń węglików typu M6C, natomiast temperatura eksploatacji leżała poza zakresem wydzielania faz wtórnych węglików typu M23C6 i faz topologicznie zwarcie wypełnione σ lub μ. Hastelloy X w stanie przesyconym charakteryzuje się bardzo dobrą spawalności, jednakże może ona ulec obniżeniu w wyniku obecności kruchych i niskotopliwych faz powstałych w trakcie eksploatacji. Microstructure and properties of repair welds with the use of Hastelloy X alloy in the delivery condition and after long term service Abstract The aim of the present study was to characterize repair welds performed on solid solution strengthened nickel-based superalloy also known Hastelloy X. The welding process was performed using GTAW. Process was carried out on materials in solid solution condition (unaged state) and after long term service in gas turbine. In order to compare microstructural changes and properties of welds light microscopy, scanning electron microscopy and microhardness measurements were performed. Additionally, transmission electron microscopy (TEM) of the base material after long term service was carried out. TEM study was the basis for the conclusion that the operating temperature had an impact on increase the amount and diameter of M6C-type carbides. Operating temperature of the turbine part was too low to contribute to the precipitation of M23C6- type carbides and topologically closed packed phases σ and μ. Alloy in solid solution condition has excellent weldability but precipitation of brittle and low melting temperature constituents during service may affect the tendency to cracking.

W pracy przedstawiono właściwości i strukturę połączenia spawanego pomiędzy elementem ze stali eksploatowanej 14 MoV6-3 oraz elementem nowym, nieeksploatowanym, również ze stali 14 MoV6-3. Oba elementy w postaci płyt o wymiarach 110x220x20 mm połączono dwoma metodami spawania łukowego. Grań spoiny wykonano metodą spawania elektrodą nietopliwą w osłonie gazu obojętnego (TIG), natomiast wypełnienie metodą spawania elektrodą otuloną (MMAW). Pospawany element został poddany wyżarzaniu odprężającemu. Powstałe złącze spawane zostało poddane badaniom nieniszczącym: VT, PT, RT oraz badaniom niszczącym: badaniu udarności, rozciąganiu złącza, badaniom metalograficznym oraz badaniu rozkładu twardości w złączu. W wyniku badań ustalono, iż istnieje możliwość wykorzystania zastosowanych metod spawania do wykonywania remontów lub modernizacji instalacji energetycznych Abstract The paper presents the structure and properties of the weld joint between the operated steel 14MoV6-3 and a new, non-operated steel 14MoV6-3 element. Both elements in the form of plates of dimensions 110 x 220 x 20 mm were joined by two methods of arc welding. Ridge welds made by welding tungsten inert shielding gas TIG, while filling was made by welding with coated electrode MMAW. Welded item has been heat treated stress-relief annealing. The resulting joint has been subjected to non-destructive testing: VT, PT, RT and destructive testing: impact test, tensile joints, metallographic examination and testing of hardness distribution in the joint. The research found that there is a possibility to use the methods of welding for repair or upgrading of power plants structures.

International audience; Iron bis(N,N-diisopropylacetamidinate) [Fe2(µ-iPr-MeAMD)2(2-iPr-MeAMD)2] and iron bis(N,N-di-tert-butylacetamidinate) [Fe(tBu-MeAMD)2] were used as precursors for the metallorganic chemical vapor deposition (MOCVD) of iron-containing compounds including pure iron, iron carbides, Fe3C and Fe4C, and iron nitrides Fe4C. Their decomposition mechanism involves hydrogen migration followed by dissociation of the Fe–N bond and the release of free hydrogenated ligand (HL) and radicals. Surface intermediates are either released or decomposed on the surface providing Fe–N or Fe–C bonds. MOCVD experiments were run at 10 Torr, in the temperature ranges of 350–450°C with Fe2(µ−iPr-MeAMD)2(2-iPr-MeAMD)2 and 280–350°C with Fe(tBu-MeAMD)2. Films prepared from Fe2(µ−iPr-MeAMD)2(2-iPr-MeAMD)2 contain Fe, Fe3C, and Fe4C. Those prepared from Fe(tBu-MeAMD)2 contain Fe, Fe3C, and also Fe4C or Fe4N, depending on the temperature and hydrogen to precursor ratio (H/P) in the input gas. The room-temperature coercive field of films processed from Fe(tBu-MeAMD)2 is 3 times higher than that of the high temperature processed Fe4N films.

Alain N. Gleizes, Vladislav Krisyuk, Lyacine Aloui, Asiya Turgambaeva, Bartosz Sarapata, Nathalie Prud’Homme, Francois Senocq, Diane Samelor, Anna Zielinska-Lipiec, Frederic Dumestre and Constantin Vahlas 1 CIRIMAT, ENSIACET, 118 Route de Narbonne, 31077 Toulouse cedex 4, France. E-mail: constantin.vahlas@ensiacet.fr, phone: +33 562 885 670, fax: +33 562 885 600 2 Nikolaev Institute of Inorganic Chemistry SB RAS ; Ave. Lavrentiev, 3, Novosibirsk, 630090, Russia. E-mail: vladislav.krisyuk@ensiacet.fr 3 AGH University of Science and Technology (AGHUST), Al. Mickiewicza 30, PL-30 059 Krakow, Poland. E-mail : sarapata@agh.edu.pl 4 NanoMePS ; Departement de Genie Physique, INSA, 135 Avenue de Rangueil, 31077 Toulouse Cedex 4, France. E-mail : contact@nanomeps.fr

Co-Authors: Michael Feuerbacher, Carsten Thomas, Julien P. A. Makongo, Stefan Hoffmann, Wilder Carrillo-Cabrera, Raul Cardoso, Yuri Grin, Guido Kreiner, Jean-Marc Joubert, Thomas Schenk, Joseph Gastaldi, Henri Nguyen-Thi, Nathalie Mangelinck-Noël, Bernard Billia, Patricia Donnadieu, Aleksandra Czyrska-Filemonowicz, Anna Zielinska-Lipiec, Beata Dubiel, Thomas Weber, Philippe Schaub, Günter Krauss, Volker Gramlich, Jeppe Christensen, Sven Lidin, Daniel Fredrickson, Marek Mihalkovic, Wieslawa Sikora, Janusz Malinowski, Stefan Brühne, Thomas Proffen, Wolf Assmus, Marc de Boissieu, Francoise Bley, Jean-Luis Chemin, Jürgen Schreuer Abstract. The Al−Mg phase diagram has been reinvestigated in the vicinity of the stability range of the Samson phase, β-Mg2Al3 (cF1168). For the composition Mg 38.5 Al 61.5, this cubic phase, space group Fd-3m (no 227), a = 28.242(1) Å, V = 22526(2) Å3, undergoes at 214 °C a first-order phase transition to rhombohedral β′-Mg2Al3(hR293), a = 19.968(1) Å, c = 48.9114(8) Å, V = 16889(2) Å3, (i.e. 22519 Å3 for the equivalent cubic unit cell) space group R3m (no 160), a subgroup of index four of Fd-3m. The structure of the β-phase has been redetermined at ambient temperature as well as in situ at 400 °C. It essentially agrees with Samson's model, even in most of the many partially occupied and split positions. The structure of β′-Mg2Al3is closely related to that of the β-phase. Its atomic sites can be derived from those of the β-phase by group-theoretical considerations. The main difference between the two structures is that all atomic sites are fully occupied in case of the β′-phase. The reciprocal space, Bragg as well as diffuse scattering, has been explored as function of temperature and the β- to β′-phase transition was studied in detail. The microstructures of both phases have been analyzed by electron microscopy and X-ray topography showing them highly defective. Finally, the thermal expansion coefficients and elastic parameters have been determined. Their values are somewhere in between those of Al and Mg.