Influence of the isothermally formed oxide thickness and of the cooling rate on the oxide scale spallation behaviour of chromia-forming Ni-based alloys; thermogravimetry and post-mortem study - Archive ouverte HAL Accéder directement au contenu
Poster De Conférence Année : 2015

Influence of the isothermally formed oxide thickness and of the cooling rate on the oxide scale spallation behaviour of chromia-forming Ni-based alloys; thermogravimetry and post-mortem study

Elodie Conrath
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Patrice Berthod

Résumé

In addition to the isothermal oxidation rate one must often take into account the resistance of the alloys to oxide spallation when temperature varies to more completely characterize their behaviour in high temperature oxidation. The severity of this phenomenon may be dependent on a lot of parameters as the type of alloy, the minor elements present in its chemical composition, the cooling rate and the different characteristics of the external oxide scales, notably: average thickness, simple or complex constitution, grain size, defects in the scales, presence of water vapour… This is thus rather difficult for a given commercial alloy to clearly separate the effects of the too numerous involved factors. In this work we have focused the study on a ternary alloy, a cast Ni-25Cr-0.5C type which usually behaves as chromia-forming thanks to its high Cr content and the interdendritic chromium carbides network facilitating Cr diffusion, to simplify the constitution of the obtained oxide. Many oxidation tests were undertaken in dry synthetic air with various values of the isothermal stage temperature, of its duration and of the post-isothermal cooling rate. The cooling parts of the obtained mass gain curves were analysed to specify the temperature of spallation start or the temperature decrease before spallation started and the final mass variation (sometimes negative in case of severe spallation), while the percentage of surface coverage of the oxidized samples by the remaining scales was measured by image analysis.
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hal-03391596 , version 1 (21-10-2021)

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  • HAL Id : hal-03391596 , version 1

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Elodie Conrath, Patrice Berthod. Influence of the isothermally formed oxide thickness and of the cooling rate on the oxide scale spallation behaviour of chromia-forming Ni-based alloys; thermogravimetry and post-mortem study. Eurocorr 2015, Sep 2015, Graz, Austria. ⟨hal-03391596⟩
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