Transition from internal to external oxidation for binary alloys in the presence of an outer scale

Gesmundo, F.; Viani, F.

doi:10.1007/bf01072908

Cited by 112 publications

(30 citation statements)

References 10 publications

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“…At this high oxygen partial pressure and temperature, fast growing transient Fe-oxides may form. As Gesmundo and Viani [28] showed, the critical solute concentration for the transition from internal to external oxidation should increase with increased growth rate of the transient oxides. The approximate predictions of Atkinson [26] are therefore likely to slightly underestimate the values above 570°C.…”

Section: Oxidation At Lower Temperatures (650-750°c)mentioning

confidence: 96%

High Temperature Corrosion of Cast Alloys in Exhaust Environments I-Ductile Cast Irons

Tholence

Norell

2007

Oxid Met

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The oxidation behavior of two ductile cast irons was investigated in synthetic diesel and gasoline exhaust gases. The alloys were a SiMo (Fe3.86S-i0.6Mo3C) and a Ni-Resist (Fe32Ni5.3Si2.1C). Polished sections were exposed at temperatures between 650 and 1,050°C, mostly for 50 h. The oxidation product was characterized by means of SEM/EDX, AES, XPS and XRD. Iron oxides nodules formed above a continuous layer of Fe-Si-oxide for SiMo. The alloy failed in forming a continuous silica layer at low temperatures. At 850°C and above silica was formed, but austenite formation enhanced the decarburization. Escaping CO/ CO 2 increased the oxide porosity, and consequently the oxidation rate. The oxidation resistance of Ni-Resist was dependent on Cr assisting the formation of SiO 2 . However, this effect was restrained to cell boundaries in particular when water enhanced the Cr evaporation or the diffusion was slow at low temperatures. Then, the rapid oxidation left metallic Ni particles in the inner oxide.

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Section: Oxidation At Lower Temperatures (650-750°c)mentioning

confidence: 96%

High Temperature Corrosion of Cast Alloys in Exhaust Environments I-Ductile Cast Irons

Tholence

Norell

2007

Oxid Met

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“…Under conditions where both Fe and Cr can oxidize, the transient oxidation of the Fe must also be considered. Gesmundo and Viani [26] showed that the critical solute concentration increased as the rate constant for the growth of the transient oxide increased.…”

Section: Effect Of Temperature On the Selective Oxidation Of Chromiummentioning

confidence: 98%

The Effect of Water Vapor on Selective Oxidation of Fe–Cr Alloys

et al. 2008

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Binary Fe-Cr alloys containing 10 and 20 mass% Cr were studied with respect to isothermal oxidation behavior at 900 and 1,050°C in Ar-20%O 2 , Ar-7%H 2 O and Ar-4%H 2 -7%H 2 O. Thermogravimetric analyses in combination with analytical studies using SEM/EDX and Raman Spectroscopy revealed, that in atmospheres in which water vapor is the source of oxygen, Cr exhibits a higher tendency to become internally oxidized than in the Ar-O 2 gas. Contrary to previous studies which showed the presence of water vapor to affect transport processes in the scale, the present results thus reveal that the presence of water vapor also affects the transport processes in the alloy. This mechanism is an ''easy'' explanation of the frequently observed effect that Fe-Cr alloys with intermediate Cr contents (e.g. 10-20%, depending on temperature) exhibit protective chromia-rich scale formation in dry gases but breakaway type Fe-rich oxides in wet gases, provided the oxygen partial pressure is sufficiently high for Fe to become oxidized.

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“…Internal oxidation has been studied for several decades (Ref 8,(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40). The mechanism is extensively discussed in the literature.…”

Section: Effect Of Metallic Nanonetwork On the Diffusion Mechanismmentioning

confidence: 99%

Effect of Element Diffusion Through Metallic Networks During Oxidation of Type 321 Stainless Steel

Zeng

Natesan

Cai

et al. 2014

J. of Materi Eng and Perform

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A detailed study was conducted on localized oxidation on Type 321 stainless steel (321ss) using synchrotron x-ray nanobeam analysis along with Raman microscopy. The results showed the presence of metallic nanonetworks in the oxide scales, which plays an important role in the continued oxidation of the alloy at 750°C. A mechanism is proposed to explain the rapid oxidation of 321ss in complex gaseous environments at elevated temperature. Neutral metal atoms could diffuse outward, and carbon atoms could diffuse inward through the metallic nanonetworks in oxide layers. Alternately, diffusion tunnels can dramatically affect the phase composition of the oxide scales. Since the diffusion rate of neutral metal and carbon atoms through the metallic nanonetworks can be much faster than the diffusion of cations through Cr 2 O 3 , the metallic nanonetwork provides a path through the protective Cr 2 O 3 layer for the rapid outward diffusion of metallic chromium and iron atoms to the nonprotective spinel layer. This diffusion process affects the solidstate reaction near the alloy-oxide boundary, and a dense Cr 2 O 3 protective layer does not form. The classic stable structure of the oxide scales, with a dense Cr 2 O 3 layer at the bottom, is damaged by the rapid diffusion through the tunnel at the reaction front, resulting in locally accelerated oxidation. This process can subsequently lead to ''breakaway'' oxidation and catastrophic failure of the alloy.

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Transition from internal to external oxidation for binary alloys in the presence of an outer scale

Cited by 112 publications

References 10 publications

High Temperature Corrosion of Cast Alloys in Exhaust Environments I-Ductile Cast Irons

High Temperature Corrosion of Cast Alloys in Exhaust Environments I-Ductile Cast Irons

The Effect of Water Vapor on Selective Oxidation of Fe–Cr Alloys

Effect of Element Diffusion Through Metallic Networks During Oxidation of Type 321 Stainless Steel

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