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Study of the Oxidation Assisted Intergranular Cracking Mechanism on a Ni-Base Superalloy

Milanese, julien and Andrieu, Eric and Osio, Jean-Baptiste and Alexis, Joël and Bardel, Didier Study of the Oxidation Assisted Intergranular Cracking Mechanism on a Ni-Base Superalloy. (2018) In: Proceedings of the 9th International Symposium on Superalloy 718 & Derivatives: Energy, Aerospace, and Industrial Applications. (The Minerals, Metals & Materials Series book series (MMMS)). Springer, 805-815. ISBN 978-3-319-89480-5 (online)

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Official URL: https://doi.org/10.1007/978-3-319-89480-5_54

Abstract

In order to collect accurate information about the widely reported Oxidation Assisted Intergranular Cracking (OAIC) mechanism of the superalloy 718 at 650 °C in air environment, we investigated a new tensile test procedure which enables to have access to a quantitative semi-continuous assessment of the damaging process of the alloy 718 during a standard tensile test. Tensile tests were carried out on a solutionized and aged alloy 718 by varying the deformation mode of the alloy during the ongoing experiment. The semi-continuous quantification of the intergranular damage was performed after a fracture surface analysis of samples tested in both Dynamic Strain Ageing (DSA) domain and DSA-subdomain where Portevin-Le Chatelier (PLC) effect occurs. This innovative testing method allows to characterize the intergranular damage that occurs when the material is stressed with an unserrated DSA deformation mode as the alloy 718 is only sensitive to OAIC in this domain. In these conditions, the onset of the intergranular cracking process was found to be around 10% of total strain. An increase in the cracking kinetic when necking occurs was also noticed. A close connection between the intensity of the intergranular damage and the cumulated strain in DSA deformation mode before the onset of the damaging process was found. The gathered information represents a significant improvement in the understanding of still debated OAIC or Stress Corrosion Cracking (SCC) mechanisms.

Item Type:Book Section
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:Other partners > AREVA (FRANCE)
French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
Other partners > MIDIVAL (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UT3 (FRANCE)
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Deposited On:28 Feb 2019 10:49

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