Study of the High Temperature Oxidation in Vapor-rich Air of Cast Chromia-forming Nickel-based and Cobalt-based Alloys - Archive ouverte HAL Accéder directement au contenu
Poster De Conférence Année : 2014

Study of the High Temperature Oxidation in Vapor-rich Air of Cast Chromia-forming Nickel-based and Cobalt-based Alloys

Lionel Aranda
Thierry Schweitzer
  • Fonction : Auteur
  • PersonId : 1125353
Albert Leroy
  • Fonction : Auteur

Résumé

Water vapor plays a particularly important role in the oxidation of the hottest pieces of jet engine and steam turbines for energy production. It may influence the high temperature oxidation which occurs for blades, as already observed in the cases of pure metals, intermetallic compounds, metallic coatings, alloys based on heavy refractory metals and ceramic materials. Water vapor is effectively known to modify the structural characteristics of the externally growing oxide scales (with consequences on the rates of mass gain or of mass loss) and acts on the adherence of the external scale during isothermal oxidation as well as when temperature varies. The Cr-rich superalloys which resist high temperature oxidation by developing an external continuous chromia scale are especially sensitive to the presence of water vapor. Indeed their protective Cr2O3 scale can be affected by a re-oxidation described by the following equation: ½ Cr2O3 (s) + H2O(g) + ¾ O2(g) → CrO2(OH)2(g). The oxy-hydroxides are volatile for temperatures high enough. For example, several works showed that volatilization into gaseous CrO2(OH)2 may start to be significant at temperatures as low as 600°C for binary or commercial Fe-based chromia-forming alloys. Such volatilization phenomenon induces, when the oxidation progress is followed by thermogravimetry, an underestimation of the mass gain rate and then of the oxidation kinetic. The high temperature oxidation behaviors of a Ni-25Cr alloy and of a Co-10Ni-30Cr alloy (contents in wt.%), respectively bases of many nickel-based and cobalt-based superalloys, were studied between 1000 and 1300°C in {water vapor}-enriched air: mass gain kinetics (thermogravimetry runs) and post-mortem characterization. For the Ni-based alloy the results were compared to the ones obtained in parallel for the same alloys oxidized in dry air, allowing evidencing the effect of water vapor for several aspects of high temperature oxidation. For the Co-based alloy only the results in dry air are available, this being due to problems encountered with the apparatus before performing the thermogravimetry tests in humidifed air. Thus, the presence of rather high water vapor in hot air did not significantly change the high temperature oxidation behaviors of the chromia-forming nickel-based alloy. The behavior was not really deteriorated in humidified air (for the two contents tested) in term of oxidation kinetic (except an enhanced chromia volatilization at very high temperature). On the contrary a better adherence of the oxide scales on the alloy’s surface was observed during the post-isothermal stage cooling, which lets think that water vapor may be favorable to a better behavior in thermal cycling. The next step of this work will be thermogravimetry tests of the Co-based alloy in wet air, which were unfortunately not realized because of problems met with the vapor generator.
Fichier principal
Vignette du fichier
072 POSTER ISHOC2014Hakodate PB LA TS AN AL.pdf (1.61 Mo) Télécharger le fichier
Origine : Fichiers produits par l'(les) auteur(s)

Dates et versions

hal-03563895 , version 1 (10-02-2022)

Identifiants

  • HAL Id : hal-03563895 , version 1

Citer

Patrice Berthod, Lionel Aranda, Thierry Schweitzer, Alexandre Navet, Albert Leroy. Study of the High Temperature Oxidation in Vapor-rich Air of Cast Chromia-forming Nickel-based and Cobalt-based Alloys. ISHOC 2014, Jun 2014, Hakodate, Japan. ⟨hal-03563895⟩
8 Consultations
11 Téléchargements

Partager

Gmail Facebook X LinkedIn More