Oxide phases and residual stresses in scales formed at early stages of oxidation of Β-NiAl at 1473 K and the effect of implanted yttrium - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Materials and Corrosion Année : 2017

Oxide phases and residual stresses in scales formed at early stages of oxidation of Β-NiAl at 1473 K and the effect of implanted yttrium

Résumé

Oxide phases formed at early oxidation stages on unmodified and yttrium-implanted β-NiAl intermetallic compound were studied with the aid of photoluminescence spectroscopy in scales developed at 1473 K for oxidation periods of up to 4 h. Two-stage-oxidation exposures with18O2-tracer were applied. The PLS method was also used to assess the residual stresses in α-Al2O3scale at consecutive stages of its development. It was found that scale formation occurs in a very local way, related to inhomogeneous distribution of Cr in substrate: sometimes distances as short as 10–15 μm were sufficient to observe entirely different phases in the scale. In general, implanted yttrium was found to retard the formation of a stable and protective layer of α-Al2O3. Oxidation for 4 h was necessary for no transient aluminum oxides (mostly θ and/or δ) to be detected, while on non-implanted material they were not found after only 26 min exposure. Only compressive stresses were found in α-alumina scales. They were rather high, reaching even 5 GPa. However, their dependence on the regions in the scale and the scale evolution stage was observed. The results indicate that patches frequently observed in scales on β-NiAl are regions where the phase transformation of transient aluminas to the α phase occurs preferentially. Ridges, which fill the transformation-related cracks, consisted only of α-Al2O3. Combination of these results with those obtained using SIMS distribution analyses of oxygen isotopes as well as with SEM/EDX, enabled very precise conclusions to be inferred concerning the scale growth mechanism. In particular, the local nature of the scale development can be described in more detail. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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Dates et versions

hal-02182091 , version 1 (12-07-2019)

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J. Jedliński, R. Gołdyn, Jean-Luc Grosseau-Poussard, G. Bonnet, K. Kowalski, et al.. Oxide phases and residual stresses in scales formed at early stages of oxidation of Β-NiAl at 1473 K and the effect of implanted yttrium. Materials and Corrosion, 2017, 68 (2), pp.235--248. ⟨10.1002/maco.201508774⟩. ⟨hal-02182091⟩
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