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Article Dans Une Revue Oxidation of Metals Année : 2014

Kinetics of High Temperature Oxidation and Chromia Volatilization for HfC-Containing Nickel-Based Alloys

Elodie Conrath
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Patrice Berthod

Résumé

Many cast chromia-forming nickel-based superalloys are reinforced by carbides. In such alloys the primary chromium carbides or tantalum carbides rapidly lose their strengthening effect in service at high temperature because of decrease in volume fraction and morphology evolution. Other carbides, HfC for example, are more stable at high temperature and they can be candidates for the reinforcement of this type of superalloy. In this work, three nickel-based alloys containing 25 wt.%Cr, 0.25 or 0.50 wt.%C, and Hf with contents high enough (3.7 and 5.6 wt.%) to promote the formation of numerous primary HfC carbides, were elaborated by foundry. They were tested in oxidation by air during 46h at 1200°C, with thermogravimetry measurement and metallographic characterization. All the mass gain curves obtained are parabolic and the oxidation rates of the studied alloys are only slightly faster than for corresponding ternary nickel alloys containing the same chromium and carbon quantities. The obtained values of the parabolic constant k p and of the chromia volatilization constant k v , deduced by applying the {m × dm/dt = k p-k v × m} method, are typical of a chromia-forming behavior. However, small quantities of HfO2 and NiCrTaO4 oxides are noticed in addition to the chromia scale. In the bulk, the volume fraction and morphology of the HfC carbides only changed a little.
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Dates et versions

hal-02181307 , version 1 (12-07-2019)

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Elodie Conrath, Patrice Berthod. Kinetics of High Temperature Oxidation and Chromia Volatilization for HfC-Containing Nickel-Based Alloys. Oxidation of Metals, 2014, 81 (3-4), pp.393-405. ⟨10.1007/s11085-013-9449-0⟩. ⟨hal-02181307⟩
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