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Modélisation et étude expérimentale de la corrosion d’un alliage chromino-formeur par des liquides silicatés

Abstract : High temperature corrosion of alloys induced by molten glasses is an issue encountered in several industrial processes such as nuclear waste vitrification or glass fiber production. Nickel-based alloys containing a large amount of chromium are especially interesting for these applications, notably due to their good corrosion resistance thanks to their ability to develop an homogeneous and covering chromia (Cr2O3) layer through high temperature oxidation Due to its low solubility in molten silicates, this layer protects the alloy from a fast corrosion induced by the glass. When put in contact with the corrosive medium at high temperature, the chromia layer is submitted to a competition between its dissolution by the molten glass and its simultaneous formation by oxidation of the alloy. The complete dissolution of the scale is called depassivation and is detrimental because it leads to an accelerated corrosion of the alloy due to a direct contact with the melt. The stability of the oxide scale is the key point for optimizing the materials lifetime. Thus, the phenomena ruling the stability or not of the oxide scale must be fully understood. In fine, the development of forecasting tools might allow to optimize the materials and the operating conditions of the industrial processes. To answer to these issues, the Ni-30Cr model alloy was selected so as binary Na2O-SiO2 and ternary Na2O-B2O3-SiO2 glass compositions. The conditions (temperature and composition) ensuring the stability of the oxide scale developed on the immersed alloy are studied through an experimental approach. A modelling of the alloy corrosion is then proposed, which allows to define the parameters forecasting the oxide scale stability. The study of the model reveals that the depassivation is linked to a lack of O2 in the liquid, which limits the formation kinetic of the oxide. The model is validated after comparison with experimental results.
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Submitted on : Wednesday, February 24, 2021 - 10:48:42 AM
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  • HAL Id : tel-03150843, version 1

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Victor Szczepan. Modélisation et étude expérimentale de la corrosion d’un alliage chromino-formeur par des liquides silicatés. Matériaux. Université de Lorraine, 2020. Français. ⟨NNT : 2020LORR0169⟩. ⟨tel-03150843⟩

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