A Possible Mechanism for Protrusions Formation at the Metal/Oxide Interface During Short Time Oxidation of Ferritic Stai
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A Possible Mechanism for Protrusions Formation at the Metal/Oxide Interface During Short Time Oxidation of Ferritic Stainless Steel Je´roˆme Issartel • Rafael Estevez • Guillaume Parry Vale´rie Parry • Se´bastien Martoia • Yves Wouters
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Received: 20 June 2012 / Published online: 27 December 2012 Ó Springer Science+Business Media New York 2012
Abstract High temperature oxidation of ferritic stainless steel for short durations leads to the formation of an original morphology at the metal/oxide interface. This interface is composed of metallic protrusions localized in a chromium-rich oxide layer through a discontinuous silica film. In this paper we propose a mechanism based on preferential diffusion paths for the oxygen through the oxide that are governed by the distribution of the hydrostatic pressure in this layer. We point out that the mechanical contrast between the oxide and the metal subjected to creep can be critical for the hydrostatic pressure gradient magnitude inside the oxide layer. This observation is likely to promote the formation of protrusions for specific conditions of temperature and time of exposure to oxidation. Keywords Stainless steel Oxidation Interface Modeling Finite element method Stress assisted diffusion
J. Issartel R. Estevez (&) G. Parry V. Parry Y. Wouters SIMaP, UMR CNRS 5266, Grenoble INP, UJF, BP 75, 38402 Saint Martin D’heres Cedex, France e-mail: [email protected] J. Issartel e-mail: [email protected] G. Parry e-mail: [email protected] V. Parry e-mail: [email protected] Y. Wouters e-mail: [email protected] J. Issartel S. Martoia APERAM Isbergues Research & Development, BP 15, 62330 Isbergues, France e-mail: [email protected]
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Oxid Met (2013) 79:65–72
Introduction Oxidations of a few tens of seconds at high temperature are carried out in the industrial processing line of stainless steel flat product after cold rolling. These heat treatments take place in order to recrystallize the cold work material. If the steel is annealed under an oxidizing atmosphere, a thin oxide film is formed on the surface. The oxide films growing on ferritic stainless steel Fe–18 wt% Cr are generally composed of a duplex layer with a chromium rich oxide in the inner part and a manganese chromium spinel oxide in the outer part [1–4]. A silica precipitation is also reported at the metal/oxide interface [5, 6]. In previous works dedicated to the characterization of the metal/oxide interface, an original morphology was highlighted with metallic protrusions bulging out through the silica layer [7–9]. In these previous works, protrusions were investigated using advanced microscopic techniques such as SEM-FEG/FIB. We concluded that the nucleation of a silica layer at the metal/oxide interface is a key reason for the establishment of this internal interface morphology. Indeed, a non-uniform precipitation of silica at the metal/oxide interface, and the laterally growth of
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