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Loriers, H.; Lafon, A.; Darras, R.; Baque, P.
CEA Saclay, 91 - Gif-sur-Yvette (France)1968
CEA Saclay, 91 - Gif-sur-Yvette (France)1968
AbstractAbstract
[en] At 600 deg. C in an atmosphere of carbon dioxide, zirconium and its alloys undergo corrosion which presents two aspects simultaneously: - formation of a surface layer of zirconia, - dissolution of oxygen in the alloy sub-layer leading to brittleness. The two phenomena greatly restrict the possibilities of using zirconium alloys as a canning material for fuel elements in CO2 cooled nuclear reactors. An attempt has thus been made to limit, and perhaps to suppress, the corrosion effects in zirconium under these conditions by protecting it with metallic coatings. A first attempt to obtain a protection using copper-based coatings did not produce the result hoped for. Aluminium coatings produced by vacuum evaporation, followed by a consolidating thermal treatment make it possible to prevent the formation of the zirconia layer, but they do not eliminate the hardening effect produced by oxygen diffusion. On the other hand, electrolytically produced chromium deposits whose adherence is improved by a thermal vacuum treatment, counteract both these phenomena simultaneously. A similar result has been obtained with coatings of molybdenum produced by the technique of high-frequency inductive plasma sputtering. The particular effectiveness of the last two types of coatings is due to their structures characterized by the existence of an adherent film of chromium or molybdenum in the free state. (authors)
[fr]
Le zirconium et ses alliages subissent, en atmosphere de gaz carbonique vers 600 deg. C, une corrosion qui prend deux aspects simultanes: - formation d'une couche de zircone superficielle, - dissolution fragilisante de l'oxygene dans l'alliage sous-jacent. Ces deux phenomenes restreignent fortement les possibilites d'utilisation des alliages de zirconium comme materiaux de gaine d'elements combustibles pour reacteurs nucleaires refroidis par le gaz carbonique. Il a donc ete cherche a limiter, voire supprimer, les effets de la corrosion du zirconium dans ces conditions, en le protegeant par des revetements metalliques. Une premiere tentative de protection par des revetements a base de cuivre n'a pas conduit au resultat escompte. Des revetements d'aluminium realises par evaporation sous vide, suivie d'un traitement thermique de consolidation, permettent deja d'eviter la formation de la couche de zircone, mais ne suppriment pas le durcissement du support par diffusion de l'oxygene. Par contre, des revetements electrolytiques de chrome, dont l'adherence est amelioree par un traitement thermique sous vide, suppriment a la fois ces deux-phenomenes. Un resultat similaire a ete obtenu avec des revetements de molybdene, realises en faisant appel a la technique de pulverisation par plasma inductif haute frequence. L'efficacite particuliere des deux derniers types de revetements s'explique par leurs constitutions, caracterisees par la subsistance d'une pellicule adherente de chrome ou de molybdene a l'etat libre. (auteurs)Original Title
Protection du zirconium et de ses alliages par des revetements metalliques
Primary Subject
Source
1968; [20 p.]; Congress of the fiftieth anniversary of the society of industrial chemistry, corrosion days; Congres du cinquantenaire de la Societe de Chimie Industrielle, journees de corrosion; Paris (France); 27-29 May 1968; 16 refs.
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Report
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Conference
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ALUMINIUM, CARBON DIOXIDE, CHEMICAL REACTION KINETICS, CHROMIUM, COPPER, CORROSION PROTECTION, DIFFUSION, ELECTROCHEMICAL COATING, FUEL CANS, HARDENING, KNOOP HARDNESS, MOLYBDENUM, OXYGEN, PERMEABILITY, PLASMA ARC SPRAYING, THERMAL EXPANSION, VAPOR DEPOSITED COATINGS, VICKERS HARDNESS, ZIRCONIUM ALLOYS, ZIRCONIUM OXIDES
ALLOYS, CARBON COMPOUNDS, CARBON OXIDES, CHALCOGENIDES, CHEMICAL COATING, COATINGS, DEPOSITION, ELEMENTS, EXPANSION, KINETICS, METALS, NONMETALS, OXIDES, OXYGEN COMPOUNDS, PHYSICAL PROPERTIES, REACTION KINETICS, REFRACTORY METALS, SPRAY COATING, SURFACE COATING, TRANSITION ELEMENT ALLOYS, TRANSITION ELEMENT COMPOUNDS, TRANSITION ELEMENTS, ZIRCONIUM COMPOUNDS
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