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Constrained sintering of an air-plasma-sprayed thermal barrier coating / A.C.F. Cocks in Acta materialia, Vol. 58 N° 12 (Juillet 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 12 (Juillet 2010) . - pp. 4233–4244 Titre : Constrained sintering of an air-plasma-sprayed thermal barrier coating Type de document : texte imprimé Auteurs : A.C.F. Cocks, Auteur ; N.A. Fleck, Auteur Année de publication : 2011 Article en page(s) : pp. 4233–4244 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Sintering  Coatings  Variational  methods  Micromechanical  modelling  Creep Résumé : A micromechanical model is presented for the constrained sintering of an air-plasma-sprayed, thermal barrier coating upon a thick superalloy substrate. The coating comprises random splats with intervening penny-shaped cracks. The crack faces make contact at asperities, which progressively sinter in-service by interfacial diffusion, accommodated by bulk creep. Diffusion is driven by the reduction in interfacial energy at the developing contacts and by the local asperity contact stress. At elevated operating temperature, both sintering and creep strains accumulate within the plane of the coating. The sensitivities of sintering rate and microstructure evolution rate to the kinetic parameters and thermodynamic driving forces are explored. It is demonstrated that the sintering response is governed by three independent timescales, as dictated by the material and geometric properties of the coating. Finally, the role of substrate constraint is assessed by comparing the rate of constrained sintering with that for free sintering. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645410002314 [article] Constrained sintering of an air-plasma-sprayed thermal barrier coating [texte imprimé] / A.C.F. Cocks, Auteur ; N.A. Fleck, Auteur . - 2011 . - pp. 4233–4244. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 12 (Juillet 2010) . - pp. 4233–4244 Mots-clés : Sintering  Coatings  Variational  methods  Micromechanical  modelling  Creep Résumé : A micromechanical model is presented for the constrained sintering of an air-plasma-sprayed, thermal barrier coating upon a thick superalloy substrate. The coating comprises random splats with intervening penny-shaped cracks. The crack faces make contact at asperities, which progressively sinter in-service by interfacial diffusion, accommodated by bulk creep. Diffusion is driven by the reduction in interfacial energy at the developing contacts and by the local asperity contact stress. At elevated operating temperature, both sintering and creep strains accumulate within the plane of the coating. The sensitivities of sintering rate and microstructure evolution rate to the kinetic parameters and thermodynamic driving forces are explored. It is demonstrated that the sintering response is governed by three independent timescales, as dictated by the material and geometric properties of the coating. Finally, the role of substrate constraint is assessed by comparing the rate of constrained sintering with that for free sintering. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645410002314