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Contribution à la mise au point de matériaux métalliques pour les unités de production d'hydrogène par vaporéformage du gaz naturel : 1/ Étude de l'oxydation de matériaux de structure à l'air entre 650 et 1050°C. 2/ Élaboration de revêtements et étude de leur résistance à l'oxydation

Abstract : The LokiR project aims to develop new steam reforming reactor to optimize the production of hydrogen. In this context, the protection of metallic alloys composing the reactor must be improved. In this thesis, the behavior of two chromia-forming alloys (Haynes© 120 and 230) was studied at high temperature under oxidizing conditions and protective coatings, able to improve their resistance against oxidation, have been developed. The study reveals that the alloys protect themselves by the growth of a chromia layer during their oxidation in air in the range 650-1050°C. This leads to a parabolic-like oxidation kinetics with low constant values for these types of alloys. The magnitude of the alloys life time at 1000°C was estimated at about 8 years in air. Chromia growth is controlled by the diffusion of the oxygen vacancy defect as well as high and low oxygen pressure. The tests indicate that the chromization of Haynes© 120 alloy leads an alpha-(Cr, Fe, Ni) phase that can be enriched with silicon. However, the behavior of these coatings oxidation at 1050°C, is, overall, unsatisfactory. The aluminization of the alloy Haynes © 120 leads to the formation of a beta-Al (Ni, Fe, Cr) coating. The oxidation study of the alloy thus coated leads to the initial growth of a transition alumina and, then, to the growth of the steady alpha-Al2O3. This last reduces the rate of oxidation and improves the thermal shock resistance. The aluminized alloy maintains the alumina-forming nature at least 10000 hours at 1000°C
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Xavier Ledoux. Contribution à la mise au point de matériaux métalliques pour les unités de production d'hydrogène par vaporéformage du gaz naturel : 1/ Étude de l'oxydation de matériaux de structure à l'air entre 650 et 1050°C. 2/ Élaboration de revêtements et étude de leur résistance à l'oxydation. Autre [cond-mat.other]. Université de Lorraine, 2012. Français. ⟨NNT : 2012LORR0017⟩. ⟨tel-01749164⟩

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