Influence of water vapour in air and of TaC carbides in alloy on the high temperature oxidation of cobalt-based refractory alloys. Part 2: Kinetic results in oxidation in wet air and comparison with dry air - Archive ouverte HAL Accéder directement au contenu
Poster De Conférence Année : 2015

Influence of water vapour in air and of TaC carbides in alloy on the high temperature oxidation of cobalt-based refractory alloys. Part 2: Kinetic results in oxidation in wet air and comparison with dry air

Lionel Aranda
Patrice Berthod
Elodie Conrath
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Résumé

It is widely recognized that water vapour plays an important role, but not necessarily unfavourable for the sustainability of the metallic component. If it is true that the presence of water vapour in air tends to provoke the volatilization of SiO2 and Al2O3 protecting the silica or alumina-forming alloys, and to accelerate of Cr2O3 covering for the chromia-forming ones, some advantages were also noticed: sometimes a slow-down in speed for the oxidation rate and frequently an improvement of the scale adherence when temperature varies. In the case of the Cr2O3-forming superalloys many studies dealing with the effect of water vapour on the high temperature oxidation concern nickel-based alloys. In contrast, the cobalt-based alloys, although they constitute also an important family of cast and wrought chromia-forming high temperature alloys, were curiously less studied in this field. Since such alloys are also used in the hottest parts of aeroengines and in the hottest pieces involved in various industrial processes (such glass working), with in both cases the possible presence of water vapour even in little concentration, it appears interesting to better know the effect of water vapour on the behaviour in oxidation at high temperature for this family of alloys. In this work, a model Co-10Ni-30Cr-0.5C-7.5Ta was considered (all contents in wt.%). This rather simple alloy, which is however close to commercial Co-based superalloys as MarM-509 and others, was subjected, in a thermo- balance, to oxidation at high temperature in synthetic air humidified with a special apparatus. The mass gain files were analysed according to the {m x dm/dt = Kp – Kv x m} method to determine the oxidation rate and the chromia-volatilization one, simultaneously. The heating part and the cooling parts of the mass gain files were also exploited to specify the oxidation start temperature and the parameters characterizing the resistance of the scale to spallation. The results were compared to the ones presented last year and to others presented this year, to evidence the effects of the presence of water vapour and of the presence of tantalum carbides. The results of the metallographic characterization of the oxidized samples will be presented next year.
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hal-03377241 , version 1 (14-10-2021)

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  • HAL Id : hal-03377241 , version 1

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Lionel Aranda, Thierry Schweitzer, Pascal Villeger, Patrice Berthod, Elodie Conrath. Influence of water vapour in air and of TaC carbides in alloy on the high temperature oxidation of cobalt-based refractory alloys. Part 2: Kinetic results in oxidation in wet air and comparison with dry air. Eurocorr 2015, Sep 2015, Graz, Austria. ⟨hal-03377241⟩
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