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Effect of exposure in steam or argon on the creep properties of Ni-based alloys / S. Dryepondt in Materials and corrosion, Vol. 63 N° 10 (Octobre 2012) 

Public ISBD [article]  in Materials and corrosion > Vol. 63 N° 10 (Octobre 2012) . - pp. 889–895 Titre : Effect of exposure in steam or argon on the creep properties of Ni-based alloys Type de document : texte imprimé Auteurs : S. Dryepondt, Auteur ; K. A. Unocic, Auteur ; B. A. Pint, Auteur Année de publication : 2013 Article en page(s) : pp. 889–895 Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Creep;  gamma  prime  precipitates;  Ni  based  superalloys;  oxidation;  steam Résumé : Although expensive, Ni-based superalloys are of interest for the ultrasupercritical steam program because of their good creep and oxidation resistance at temperatures above 700 °C. As the effect of steam oxidation on the alloy mechanical properties is unknown, creep specimens of alloy CCA617, 740, and 230 were pre-oxidized for 2000 and 4000 h in steam at 800 °C before testing in air at the same temperature. Compared with as fabricated material, exposure in steam decreased the creep properties of alloy CCA617, had less of an effect on alloy 740, and did not affect alloy 230. Testing of a specimen repolished after steam exposure as well as microstructural observations indicate that the oxidation affected zone at the specimen surface is not responsible for the properties degradation. Surprisingly, a similar time anneal in an inert environment resulted in a drastic decrease of creep rupture life and an increase in the creep rate and elongation at rupture. Transmission electron microscopy analysis revealed that the mechanical properties decrease for alloy CCA617 is related to the absence of γ′ precipitates within the grains. En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201206694/abstract [article] Effect of exposure in steam or argon on the creep properties of Ni-based alloys [texte imprimé] / S. Dryepondt, Auteur ; K. A. Unocic, Auteur ; B. A. Pint, Auteur . - 2013 . - pp. 889–895. Génie mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 63 N° 10 (Octobre 2012) . - pp. 889–895 Mots-clés : Creep;  gamma  prime  precipitates;  Ni  based  superalloys;  oxidation;  steam Résumé : Although expensive, Ni-based superalloys are of interest for the ultrasupercritical steam program because of their good creep and oxidation resistance at temperatures above 700 °C. As the effect of steam oxidation on the alloy mechanical properties is unknown, creep specimens of alloy CCA617, 740, and 230 were pre-oxidized for 2000 and 4000 h in steam at 800 °C before testing in air at the same temperature. Compared with as fabricated material, exposure in steam decreased the creep properties of alloy CCA617, had less of an effect on alloy 740, and did not affect alloy 230. Testing of a specimen repolished after steam exposure as well as microstructural observations indicate that the oxidation affected zone at the specimen surface is not responsible for the properties degradation. Surprisingly, a similar time anneal in an inert environment resulted in a drastic decrease of creep rupture life and an increase in the creep rate and elongation at rupture. Transmission electron microscopy analysis revealed that the mechanical properties decrease for alloy CCA617 is related to the absence of γ′ precipitates within the grains. En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201206694/abstract