The formation of aluminum oxide scales on high-temperature alloys

Prescott, R.; Graham, M. J.

doi:10.1007/bf00666913

Cited by 430 publications

(203 citation statements)

References 108 publications

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“…2). The generally accepted mechanism for the growth of such an alumina layer is the inward diffusion of oxygen along oxide grain boundaries [33,34]. If diffusion through the scale is rate-limiting, the experimental growth kinetics can usually be described with a parabolic growth law [9,10].…”

Section: Resultsmentioning

confidence: 99%

Effect of Y Distribution on the Oxidation Kinetics of NiCoCrAlY Bond Coat Alloys

Nijdam

Sloof

2007

Oxid Met

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The relation between the Y distribution in the alloy and the growth kinetics of the developing oxide scale was studied for the thermal oxidation of two .2Y (at.%) alloys at 1,373 K: (i) a coarse-grain cast alloy with large Ni 5 Y intermetallic precipitates, and (ii) a fine-grain freestanding coating with small Ni 5 Y precipitates. Using a combination of experiments and model calculations, it is shown that the average growth kinetics of a NiCoCrAlY alloy are dependent on the size and distribution of Y-rich oxide inclusions (pegs) in the a-Al 2 O 3 oxide layer. Alumina scales containing a high density of small Y-oxide inclusions grow faster than a-Al 2 O 3 scales containing only a few, large Y-oxide inclusions. Upon oxidation of the freestanding coating, the Y-oxide inclusions in the scale attain their maximum size after the Y in the coating is completely consumed. After this point, a decrease in the average oxidation kinetics occurs.

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Section: Resultsmentioning

confidence: 99%

Effect of Y Distribution on the Oxidation Kinetics of NiCoCrAlY Bond Coat Alloys

Nijdam

Sloof

2007

Oxid Met

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“…It has been argued that the Cr depletion of the external oxide and the metal substrate resulting from (1) made the formation of an external alumina scale more difficult, considering the important role played by Cr in the formation of protective alumina layers [21]. It has been suggested that the resulting iron-rich scale was porous, allowing N 2 molecules to penetrate to the alloy.…”

Section: Discussionmentioning

confidence: 99%

Cyclic Corrosion and Chlorination of an FeCrAl Alloy in the Presence of KCl

et al. 2015

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The KCl-induced corrosion of the FeCrAl alloy Kanthal Ò APMT in an O 2 ? N 2 ? H 2 O environment was studied at 600°C. The samples were pre-oxidized prior to exposure in order to investigate the protective nature of alumina scales in the present environment. The microstructure and composition of the corroded surface was investigated in detail. Corrosion started at flaws in the pre-formed a-alumina scales, i.e. a-alumina was protective in itself. Consequently, KCl-induced corrosion started locally and, subsequently, spread laterally. An electrochemical mechanism is proposed here by which a transition metal chloride forms in the alloy and K 2 CrO 4 forms at the scale/gas interface. Scale de-cohesion is attributed to the formation of a sub-scale transition metal chloride.

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“…In an ideal case, the oxide layer should be highly stable, slow growing, free from pores or cracks, adherent and coherent [18]. α-Al 2 O 3 is an oxide which comes close to satisfying these requirements.…”

Section: The Oxidation Mechanismmentioning

confidence: 99%