Cyclic oxidation of high-silicon spheroidal graphite iron

Ebel, André; Marsan, Olivier; Lacaze, Jacques; Malard, B.

doi:10.1016/j.corsci.2021.109854

Cited by 9 publications

(4 citation statements)

References 26 publications

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“…Although the current study reproduced most of these findings (oxidized graphite, duplex layer of oxide structure, and oxide phases), it did not detect any unoxidized graphite nodules within the scale. In addition, previous research suggested [24] that the silica layer transformed into fayalite and iron oxide at 800 • C. This change happened through a series of events. Ebel et al further explained that during this transformation, austenite grains formed at the boundary between the matrix and silica, which induced stress and led to fractures in the silica layer.…”

Section: Isothermal Oxidation Mechanism Of Simo and Simoalmentioning

confidence: 89%

“…It is believed that the oxidation resistance is saturated and that the addition of aluminum above 4.8% does not significantly alter the oxidation resistance. In the literature, Ebel et al [24] demonstrated that an oxide scale 130 micron thick was formed after 100 h of heating at 800 • C for SiMo nodular iron. Lakeh et al reported that thickness of the scale formed in SiMo with 3.5 wt% Si and 3 wt% Al cast iron was 5 to 15 microns at the test temperatures of 650 • C and 800 • C. Regarding cast iron oxidation, the other important finding was the nature of the decarburized graphite pits.…”

Section: Isothermal Oxidation Mechanism Of Simo and Simoalmentioning

confidence: 99%

“…Additionally, the decarburization of high-purity hot isostatic-pressed graphite resulted in an activation energy of 123 kJ/mole. Previously, Ebel et al [24] calculated the oxidation activation energy of SiMo nodular iron at 158 kJ/mol by using the oxide film thicknesses as a function of thermal cycles. Results from the current study are in alignment with these previously reported values.…”

Section: Nonisothermal Oxidation Mechanism Of Simo and Simoalmentioning

confidence: 99%

“…The scale was composed of three layers: the external layer was hematite and magnetite that expended outwards, the internal layer was magnetite (Fe 3 O 4 ) and fayalite (Fe 2 SiO 2 ) that grew into the subsurface, and there was a thin protective film of silica (SiO 2 ) at the metal/oxide interface. This thin silica film could be reacted with Fe, O, or FeO to form fayalite (Fe 2 SiO 2 ) [22][23][24]. It was also reported that the silica film was discontinuous throughout the interface but still slowed down the oxidation kinetics [25].…”

Section: Introductionmentioning

confidence: 99%

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High Temperature Oxidation Behavior of High Al-Si Alloyed Vermicular Graphite Cast Iron for Internal Combustion Engine’s Hot-End Exhaust Components

Yilmaz,

Bayata,

Solak

2024

Metals

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This study investigated the influence of high silicon (4.2 wt%) and varying aluminum (3.5–4.8 wt%) content on the high temperature oxidation behavior and thermophysical properties of SiMoAl vermicular graphite cast iron for hot-end exhaust components. Isothermal oxidation tests at 800 °C and nonisothermal oxidation tests in a dry-air atmosphere were conducted on SiMo nodular iron, along with two SiMoAl vermicular graphite cast iron variants alloyed with 3.5 wt% Al and 4.8 wt% Al. The investigations revealed the formation of a thin duplex layer of oxide scale, consisting of an iron-rich external oxide layer and continuous aluminum oxide at the metal/oxide interface. Although aluminum oxide acted as a protective barrier by impeding the solid-state diffusion of oxygen, severe subsurface oxidation was observed due to the interconnected vermicular graphite covered by aluminum oxides after decarburization. Furthermore, based on nonisothermal oxidation experiments, the effective activation energy of oxidation was found to be significantly increased by the addition of aluminum, even though the oxidation activation energies of SiMoAl samples exhibited small changes in comparison to each other. Additionally, thermophysical analysis demonstrated a substantial decrease in the thermal conductivity and a slight increase in the thermal expansion with the addition of aluminum.

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Section: Isothermal Oxidation Mechanism Of Simo and Simoalmentioning

confidence: 89%

Section: Isothermal Oxidation Mechanism Of Simo and Simoalmentioning

confidence: 99%

Section: Nonisothermal Oxidation Mechanism Of Simo and Simoalmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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High Temperature Oxidation Behavior of High Al-Si Alloyed Vermicular Graphite Cast Iron for Internal Combustion Engine’s Hot-End Exhaust Components

Yilmaz,

Bayata,

Solak

2024

Metals

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CALPHAD-Based Modeling and Experimental Validation of Silicon Effect on the Solidification Behavior of Novel SiNb Cast Irons

Aktaş Çelik,

Atapek,

Polat

et al. 2024

Metall Mater Trans A

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The low oxidation resistance of SiMo ductile cast irons used as exhaust manifold material at high temperatures necessitates the development of new generation ductile cast iron compositions. New alloy designs can be made using CALPHAD methodology, and solidification sequence, segregation and critical phase transformation temperatures can be determined, especially for the solidified bulk materials. Thus, in commercial practicality, castable compositions with a raised A1 temperature can be obtained. In this study, novel SiNb cast irons with varying silicon contents were developed as candidate materials for exhaust manifolds. Solidification sequence, microsegregation, phase transformations, equilibrium phases of hypereutectic compositions containing 4 to 7 wt pct Si were calculated by CALPHAD-based modeling. The bulk materials of the studied compositions were cast as Y blocks and metallurgical analyzes were carried out. Studies revealed that; (i) in the ferritic matrix of the cast irons, graphite, Nb-rich carbides and some pearlite existed, (ii) pearlite formation was due to the negative segregation of silicon and positive segregation of manganese during solidification, (iii) as silicon content increased the amount of silicon dissolved in ferrite phase increased in the solidified structure and as a result pearlite formation decreased at the cell boundaries, and amount of vermicular graphite increased, (iv) depending on the silicon content the critical A1 temperature varied between 860 °C to 1013 °C and these values were higher than that of SiMo cast iron. All these findings revealed that SiNb cast irons had phase stability at higher temperatures compared to SiMo cast iron.

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Initial Oxidation Stage of SiMo and SiNb-xAl Ductile Cast Irons in Air and CO2-Containing Atmospheres

2022

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Cyclic oxidation of high-silicon spheroidal graphite iron

Cited by 9 publications

References 26 publications

High Temperature Oxidation Behavior of High Al-Si Alloyed Vermicular Graphite Cast Iron for Internal Combustion Engine’s Hot-End Exhaust Components

High Temperature Oxidation Behavior of High Al-Si Alloyed Vermicular Graphite Cast Iron for Internal Combustion Engine’s Hot-End Exhaust Components

CALPHAD-Based Modeling and Experimental Validation of Silicon Effect on the Solidification Behavior of Novel SiNb Cast Irons

Initial Oxidation Stage of SiMo and SiNb-xAl Ductile Cast Irons in Air and CO2-Containing Atmospheres

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