Process for protecting alloys which are resistant when hot, especially nickel-based

The process for deposition of a protective coating on a substrate made of alloy which is resistant when hot comprises a first stage of chromium enrichment of the surface region of the substrate by gas phase diffusion without contact of the solid-solid type and a second stage of gas phase aluminising...

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Bibliographische Detailangaben
1. Verfasser:	JEAN-PAUL FOURNES, JACQUES LEOPOLD EMILE GRAMMAGNAC ET RENE JEAN MORBIOLI
Format:	Patent
Sprache:	eng ; fre
Schlagworte:	CHEMICAL SURFACE TREATMENT CHEMISTRY COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATIONOR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY IONIMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL COATING MATERIAL WITH METALLIC MATERIAL COATING METALLIC MATERIAL DIFFUSION TREATMENT OF METALLIC MATERIAL INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION INGENERAL METALLURGY SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THESURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION
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Beschreibung
Zusammenfassung:	The process for deposition of a protective coating on a substrate made of alloy which is resistant when hot comprises a first stage of chromium enrichment of the surface region of the substrate by gas phase diffusion without contact of the solid-solid type and a second stage of gas phase aluminising at low activity also without solid-solid contact. The operating conditions, additionally comprising temperatures between 1000 DEG C and 1200 DEG C and times of between 1 and 5 hours, permit the formation of an internal layer of aluminide of nickel alloyed with chromium and with other elements of the substrate by diffusion of aluminium into the nickel and an outer layer of pure and homogeneous nickel aluminide by extraction of the nickel towards the aluminium. These conditions avoid, at all stages, the formation of alpha phase in the chromium-enriched layer and then in the inner layer during the diffusion of the aluminium and also during the extraction of the nickel from this layer. LE PROCEDE DE DEPOT D'UN REVETEMENT PROTECTEUR SUR UN SUBSTRAT EN ALLIAGE RESISTANT A CHAUD COMPREND UN PREMIER STADE D'ENRICHISSEMENT EN CHROME DE LA REGION SUPERFICIELLE DU SUBSTRAT PAR DIFFUSION EN PHASE GAZEUSE SANS CONTACT DU TYPE SOLIDE-SOLIDE ET UN SECOND STADE D'ALUMINISATION EN PHASE GAZEUSE A BASSE ACTIVITE EGALEMENT SANS CONTACT SOLIDE-SOLIDE. LES CONDITIONS OPERATOIRES, COMPORTANT EN OUTRE LES TEMPERATURES ENTRE 1000C ET 1200C ET LES DUREES ENTRE 1 ET 5HEURES, PERMETTENT LA FORMATION D'UNE COUCHE INTERNE DE REVETEMENT D'ALUMINIURE DE NICKEL ALLIE AU CHROME ET AUX AUTRES ELEMENTS DU SUBSTRAT PAR DIFFUSION D'ALUMINIUM DANS LE NICKEL ET UNE COUCHE EXTERNE D'ALUMINIURE DE NICKEL PUR ET HOMOGENE PAR EXTRACTION DU NICKEL VERS L'ALUMINIUM. CES CONDITIONS EVITENT A TOUTES LES ETAPES LA FORMATION DE PHASE A, DANS LA COUCHE ENRICHIE EN CHROME PUIS DANS LA COUCHE INTERNE LORS DE LA DIFFUSION DE L'ALUMINIUM ET ENCORE LORS DE L'EXTRACTION DU NICKEL A PARTIR DE CETTE COUCHE.