Some observations on void formation in Fe3O4 layers on Fe

Hussey, R. J.; Graham, M. J.

doi:10.1016/0010-938x(81)90034-2

Cited by 17 publications

(5 citation statements)

References 3 publications

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“…But, serial sectioning combined with optical microscopy failed to detect any pores which had continuous connectivity to the metal/ oxide interface. Similar conclusions were reached by Hussey and Graham (12) for pores in Fe~O4 films grown on Fe. It is possible that the fissures responsible for inward oxygen penetration have a transient existence such that during oxidation fissures are continually being generated and are resealing.…”

Section: Discussionsupporting

confidence: 87%

Transport of Nickel and Oxygen during the Oxidation of Nickel and Dilute Nickel/Chromium Alloy

Atkinson

Smart

1988

J. Electrochem. Soc.

105

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NiO films have been grown on high-purity Ni and Ni 0.1 weight percent (w/o) Cr alloy, at 700~ and 0.21 bar, by sequential oxidation in 1602 and 1802. The distributions of oxygen, Ni, and Cr isotopes in the films were analyzed using SIMS. For both materials, the rate controlling transport process was found to be the outward diffusion of Ni through the NiO. Inward oxygen gas transport also occurs and is responsible for the growth of new oxide within the films and for the growth of the inner layer of the well-developed duplex films which grow on the alloy. A mechanism whereby oxygen gas penetrates the films through fissures to form new oxide in available space is proposed to explain the observations and the growth of duplex films.The protective properties of oxide films formed by oxidation of metals depend on the transport of reactants (metal and oxygen) through the film and the structure of the film (including the microstructure). In general, the transport properties and structure of the oxide film are inter-related. In some cases, this relationship is relatively straightforward; for example, the oxidation of high-purity Co or Ni at high temperatures, when the classical singlelayer, single-phase compact oxide film grows by outward diffusion of metal ions through the oxide lattice. At the other extreme, the relationship is extremely complicated; for example, the oxidation of a multicomponent alloy in mixed gases at intermediate temperatures. The complicating factors include multiphase, multilayered, doped oxides containing voids, dislocations, and grain boundaries as additional potential routes for transport through the oxide.Between these two extremes is an important class of oxide film microstructures known as duplex films (or scales). Duplex films are formed under a wide variety of conditions on a large number of metal substrates. They can form on high-purity metals as well as on alloys. On high-purity metals, the inner and outer layers of the duplex film are distinguishable by their different grain size. The outer layer usually has a columnar structure, and the inner layer has an equiaxed structure of much finer grain size. The thickness of the inner layer, as a fraction of the total layer thickness, appears to depend on the system and the experimental conditions. However, the inner layer thickness never exceeds the thickness of metal converted to oxide (i.e., when the inner-layer/outer-layer boundary coincides with the position of the original metal surface). When duplex films form on dilute alloys, the inner-layer/ outer-layer boundary usually coincides with the position of original alloy surface, and the alloying elements are preferentially located in the inner layer (provided that the alloying elements have low mobility in the oxide).The transport processes which occur during duplex film growth have been studied using isotopically labeled oxygen tracers in a number of systems. The results of these experiments and their interpretation have recently been reviewed by Atkinson (1). The experiments have shown tha...

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Section: Discussionsupporting

confidence: 87%

Transport of Nickel and Oxygen during the Oxidation of Nickel and Dilute Nickel/Chromium Alloy

Atkinson

Smart

1988

J. Electrochem. Soc.

105

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“…Nevertheless, no pore with continuous connectivity to the metal/oxide interface was detected. Similar conclusions were reached by Martinelli et al [4][5][6] and Hussey and Graham [20] for oxide grown respectively on T91 surface in oxygen saturated Pb-Bi and on Fe in air and CO 2 . Do they close as soon as CO 2 molecules or other oxidant species enter in which makes thus the mechanism of void-induced duplex oxide growth inadequate as some authors suggest it or can they stay opened for enough time for the proposed mechanism to process?…”

Section: Viability Of Nanochannel Formation and Existence During The supporting

confidence: 82%

Corrosion of 9Cr Steel in CO2 at Intermediate Temperature III: Modelling and Simulation of Void-induced Duplex Oxide Growth

Rouillard

Martinelli

2011

Oxid Met

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9Cr-1Mo steel forms in CO 2 at 550°C a duplex oxide layer containing an outer magnetite scale and an inner Fe-Cr rich spinel scale. The inner spinel oxide layer is formed according to a void-induced oxidation mechanism. The kinetics of the total oxide growth is simulated from the proposed oxidation model. It is found that the rate limiting step of the total oxide growth is iron diffusion through high diffusion paths such as oxide grain boundaries in the inner Fe-Cr rich spinel oxide layer. In the proposed oxidation model, a network of nanometric high diffusion paths through the oxide layer allows the very fast supply of CO 2 inside pores formed at the oxide/metal interface. Its existence is demonstrated to be physically realistic and allows explaining several observed physical features evolving in the oxide layer with time.

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“…Once arrived at the oxide/metal interface, the oxygen-bearing molecules react with the metallic elements to form the inner spinel oxide and release its linked atom H, S, C or Pb. Past studies have inferred that this porosity exists in channel form with a nanometric diameter size [23,24]. Depending on the study and the authors, the nanochannel network would be due to either cracks formed through the oxide layer because of oxide growth stresses [21,23,[25][26][27][28] or would result from oxide dissociation over voids formed at the oxide/metal interface by vacancies condensation [29,30].…”

Section: Mechanism Of Duplex Oxide Layer Formation On T91mentioning

confidence: 96%

Corrosion of 9Cr Steel in CO2 at Intermediate Temperature I: Mechanism of Void-Induced Duplex Oxide Formation

et al. 2011

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Under CO 2 exposure at an intermediate temperature, typically 550°C, 9Cr-1Mo steel forms a duplex oxide scale made of an outer magnetite layer and an almost-as-thick inner Fe-Cr rich spinel oxide layer. It is proposed that the inner Fe-Cr spinel layer grows according to a mechanism involving void formation at the oxide/ metal interface. The driving force for pore formation is the outward magnetite growth: iron vacancies are injected at the oxide/metal interface then condense into voids. The fresh metallic surface made available is then oxidized by CO 2 , which diffuses fast through the scale. The physical aspects, the integrity and the nature of the scale are shown to be very dependent on the oxygen potential existing in the environment.

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Some observations on void formation in Fe3O4 layers on Fe

Cited by 17 publications

References 3 publications

Transport of Nickel and Oxygen during the Oxidation of Nickel and Dilute Nickel/Chromium Alloy

Transport of Nickel and Oxygen during the Oxidation of Nickel and Dilute Nickel/Chromium Alloy

Corrosion of 9Cr Steel in CO2 at Intermediate Temperature III: Modelling and Simulation of Void-induced Duplex Oxide Growth

Corrosion of 9Cr Steel in CO2 at Intermediate Temperature I: Mechanism of Void-Induced Duplex Oxide Formation

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