FEG-SEM investigation of α-alumina scales formed on FeCrAlY alloys oxidised at 1200<sup>○</sup>C

Al‐Badairy, H.; Tatlock, G. J.; Fawcett, Sandra; Beahan, P.; Hunt, John A.

doi:10.1051/jp4:2005124003

Cited by 4 publications

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“…13 some being dominated by Y while others are dominated by Zr or Ti [26]. In addition to the RE elements, the oxide particles sometimes contain Si [23]. Micrometer-sized RE-rich intermetallic particles are reported to precipitate during processing because of the limited solubility of these elements in the alloy [15,16].…”

Section: Discussionmentioning

confidence: 99%

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TEM Investigation of the Microstructure of the Scale Formed on a FeCrAlRE Alloy at 900 °C: The Effect of Y-rich RE Particles

et al. 2010

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Three oxide features: the thin and smooth protective oxide, reactive element (Ti-, Zr-or Y-rich) particles, and patches of thick oxide surrounding the Y-rich reactive element particles, were observed on a commercial FeCrAlRE alloy, Kanthal AF, exposed at 900°C. The microstructural development of the patches of thick oxide was investigated on samples exposed for 24 or 168 h in either dry O 2 or O 2 ? 40% H 2 O. Analytical transmission electron microscopy in combination with site-precision TEM sample preparation by FIB/SEM was used. In all patches a thin but continuous inward growing a-Al 2 O 3 layer was formed under a thick outward growing alumina layer, which initially consisted only of c-Al 2 O 3 . In dry O 2 , transformation of c-Al 2 O 3 (in the outer layer) to a-Al 2 O 3 had started during 24 h and a considerable amount of c-Al 2 O 3 had transformed after 168 h. The transformation originated immediately above the inward growing a-Al 2 O 3 . No such transformation occurred in O 2 ? H 2 O. The possible effects of the Y-rich RE particles, as well as the effects of water vapour, on the oxidation were discussed.

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Section: Discussionmentioning

confidence: 99%

“…This effect was termed ''overdoping''. As might be expected, the effect on oxidation behaviour depends on the specific RE elements added [22][23][24]. For example, Wessel et al reports that the oxide morphology changes from columnar in a Y-containing version of a FeCrAl alloy to small equiaxed grains in a (Zr ?…”

Section: Introductionmentioning

confidence: 89%

TEM Investigation of the Microstructure of the Scale Formed on a FeCrAlRE Alloy at 900 °C: The Effect of Y-rich RE Particles

et al. 2010

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“…There are notable 'hot spots' where chains of REE particles link the outer surface of the scale with the interior. TEM work on the investigation of Y and Hf segregation 24,25 showed that Hf and Y segregate at the GB of the alumina scale in the region near scale/metal interface as elements. In the outer layer of the scale near scale/gas interface Hf and Y were found to precipitate as Y rich particles or Hf rich particles and in some cases as Y-Hf rich particles (oxide particles).…”

Section: Oxide: Other Phases and A Alumina Compositional Variationmentioning

confidence: 99%

Microstructural development of α alumina scales developed on FeCrAl alloys

Prior¹,

Al‐Badairy²,

Seward³

et al. 2006

Materials Science and Technology

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A scanning electron microscope (SEM) study was conducted of a alumina scales developed on the surface of FeCrAl alloys during high temperature oxidation, using backscattered electron imaging, cathodoluminescence (CL) imaging, electron backscatter diffraction (EBSD) and X-ray microanalysis. CL variations relate to trace element distributions and to crystallographic orientations. The compositional variations suggest that grain boundary diffusion was dominant in the scale. The a alumina grains are equiaxed at the outer scale surface and columnar between here and the metal oxide interface; both grain types have a very strong crystallographic preferred orientation (CPO): a fibre texture of r axes perpendicular to the sheet. The CPO cannot be explained by substrate control or by plastic deformation. There is a correlation of the orientation of the anisotropic elastic properties of the scale and the likely thermal stress systems: one possible explanation is that the CPO may relate to oriented oxide nucleation during heating.

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“…Without this protective scale, the coating and ultimately the substrate, would come under rapid oxidation and/or corrosion attack [5]. The durability or service life of the MCrAlY coating depends mainly on the stability of the formed alumina scale [6].…”

Section: Introductionmentioning

confidence: 99%

Corrosion Behavior of Laser Remelted CoNiCrAlY Based Composite Coatings

Uţu¹,

Mărginean²,

Şerban³

et al. 2010

ENG

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The corrosion behavior of High-Velocity Oxygen Fuel (HVOF) sprayed MCrAlY coatings obtained from CoNiCrAlY particles (wt. 8% Al) mechanically doped with Al 2 O 3 nanopowder was investigated before and after laser remelting. The latter process was applied in order to achieve a homogeneous structure as well as better mechanical properties for the coating (reduced brittleness offered by the presence of the Al 2 O 3 nanoparticles). Another important task of the laboratory investigations was the investigation of the corrosion behavior of the modified coatings. The results obtained from the potentiodynamic polarization measurements carried out in a chloride environment revealed an enhanced corrosion resistance of the laser remelted coatings comprising a refined microstructure. Microhardness measurements of the modified coatings revealed lower values in comparison with that of the samples in as-sprayed status. This observation leads to the assumption that a concomitant improvement of coatings ductility occurred as well.

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FEG-SEM investigation of α-alumina scales formed on FeCrAlY alloys oxidised at 1200^○C

Cited by 4 publications

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TEM Investigation of the Microstructure of the Scale Formed on a FeCrAlRE Alloy at 900 °C: The Effect of Y-rich RE Particles

TEM Investigation of the Microstructure of the Scale Formed on a FeCrAlRE Alloy at 900 °C: The Effect of Y-rich RE Particles

Microstructural development of α alumina scales developed on FeCrAl alloys

Corrosion Behavior of Laser Remelted CoNiCrAlY Based Composite Coatings

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FEG-SEM investigation of α-alumina scales formed on FeCrAlY alloys oxidised at 1200○C

Cited by 4 publications

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TEM Investigation of the Microstructure of the Scale Formed on a FeCrAlRE Alloy at 900 °C: The Effect of Y-rich RE Particles

TEM Investigation of the Microstructure of the Scale Formed on a FeCrAlRE Alloy at 900 °C: The Effect of Y-rich RE Particles

Microstructural development of α alumina scales developed on FeCrAl alloys

Corrosion Behavior of Laser Remelted CoNiCrAlY Based Composite Coatings

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FEG-SEM investigation of α-alumina scales formed on FeCrAlY alloys oxidised at 1200^○C