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Formation par cémentation activée de revêtements à base de siliciures de fer et de chrome destinés à assurer la protection du niobium et de ses alliages contre l'oxydation à haute température

Abstract : The aim of this study is to improve the properties of a silicide coating contanung niobium (colombium), iron, and chromium. An experimental study of the quaternary phase diagram of this system at 1200°C is achieved with the atomic percent amount of silicium include between 33 and 50. This study brought out sorne new quaternary silicides and the equilibrium path between each one. Sorne of these phases were studied with more accuracy : their chemical composition, their crystallographic structure, and their oxidation resistance. The exchanges of titanium instead of niobium, of cobalt or nickel instead of chromium were used to improve physical and chemical properties. AlI this work brought out the best resistant silicides in isothermal oxidation which were included in new coatings . An other part of this work was the improvement of the pack-cementation process : • by a systematic study of the role of different parameters such as the cleaning and geometry of samples, the non-polluting effect of dilution powder, and the composition of the substrate material (pure niobium or alloys), • by the study of the mechanism of pack-cementation process when gaseous diffusion or solid state diffusion is predominant. Finally, a comparative study of the different coatings properties in cyclic oxidation confirmed the industrial standard coating good resistance, and showed a new coating open to be better than the previous one
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Theses
File URL :
http://docnum.univ-lorraine.fr/prive/SCD_T_1996_0113_BREQUEL.pdf
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https://hal.univ-lorraine.fr/tel-01747938
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Submitted on : Thursday, March 29, 2018 - 11:13:35 AM
Last modification on : Wednesday, March 24, 2021 - 10:24:04 AM

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  • HAL Id : tel-01747938, version 1

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Hervé Bréquel. Formation par cémentation activée de revêtements à base de siliciures de fer et de chrome destinés à assurer la protection du niobium et de ses alliages contre l'oxydation à haute température. Autre. Université Henri Poincaré - Nancy 1, 1996. Français. ⟨NNT : 1996NAN10113⟩. ⟨tel-01747938⟩

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