TiO2 nanoparticles-assisted α-Al2O3 direct thermal growth on nickel aluminide intermetallics: Template effect of the oxide with the hexagonal oxygen sublattice

ABSTRACTThe transition metal ions Fe, Mn, Ni, Ti, and Cr as well as the group III-A ion Ga were implanted in a random direction close to the c-axis of α-Al2O3 single crystals. These were subsequently annealed in flowing oxygen at temperatures between 600 and 1500°C. The impurity and damage distributions were determined by He backscattering and channeling techniques. The normally trivalent ions, Fe, Ga, and Cr show strong tendency to become incorporated into substitutional sites, whereas the normally divalent ions, Cu and Mn show no such tendency, even at high temperatures. Most of the impurities tend to move toward the surface with only Fe, Ga, and Cr showing tendency towards bulk diffusion. In all cases the Al sublattice recovers at lower temperatures than the oxygen sublattice.

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Elaboration of Nickel Aluminide Diffusion Coatings: Application to Oxidation Resistance

Materials Science Forum ◽

10.4028/www.scientific.net/msf.595-598.41 ◽

2008 ◽

Vol 595-598 ◽

pp. 41-49 ◽

Cited By ~ 2

Author(s):

Céline Choux ◽

Sébastien Chevalier ◽

Yannik Cadoret

Keyword(s):

High Temperature ◽

Nickel Aluminide ◽

Diffusion Mechanism ◽

Alumina Scale ◽

Organic Chemical ◽

Material Surface ◽

Protective Oxide ◽

Diffusion Coatings ◽

Aluminide Coatings ◽

Α Al2o3

Aluminide diffusion coatings are widely used in aeronautic domain. Nickel based superalloys present good mechanical properties and creep resistance at high temperature but their corrosion resistance is somewhat poor. In order to enhance their lifetime at high temperature, aluminide coatings can be applied on alloy surface. Aluminium present on material surface can form, at high temperature, alumina scale which is a protective oxide scale. In the present study, nickel aluminide coatings were carried out by aluminisation in a single step pack cementation process on nickel based superalloys 600 and AM1. Ni-Al intermetallic was obtained in each case. Oxidation tests were carried out at 900°C in air under atmospheric pressure. At this temperature, transient alumina as γ-Al2O3 and θ-Al2O3 appear on surface and are less protective than the stable α- Al2O3. Reactive elements can enhance α-Al2O3 nucleation and change diffusion mechanism during oxidation leading to a better adherence of alumina scale. In the present work, yttria was introduced by Metal-Organic Chemical Vapour Deposition (MOCVD) prior to the aluminisation. Yttria doped and undoped sample behaviours were compared under oxidising atmospheres.

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The crystallographic template effect assisting the formation of stable α-Al2O3 during low temperature oxidation of Fe–Al alloys

Corrosion Science ◽

10.1016/j.corsci.2016.01.007 ◽

2016 ◽

Vol 105 ◽

pp. 100-108 ◽

Cited By ~ 13

Author(s):

Pedro Brito ◽

Haroldo Pinto ◽

Aleksander Kostka

Keyword(s):

Low Temperature ◽

Al Alloys ◽

Low Temperature Oxidation ◽

Template Effect ◽

Temperature Oxidation ◽

Α Al2o3

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The wustite-spinel interface

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100126226 ◽

1987 ◽

Vol 45 ◽

pp. 268-269

Author(s):

S.R. Summerfelt ◽

C.B. Carter

Keyword(s):

Solid State ◽

Solid State Reaction ◽

Strain Energy ◽

Matrix Material ◽

Lattice Misfit ◽

Solid State Reactions ◽

Oxygen Sublattice ◽

Large Particles ◽

Small Lattice ◽

Coherent Interfaces

The wustite-spinel interface can be viewed as a model interface because the wustite and spinel can share a common f.c.c. oxygen sublattice such that only the cations distribution changes on crossing the interface. In this study, the interface has been formed by a solid state reaction involving either external or internal oxidation. In systems with very small lattice misfit, very large particles (>lμm) with coherent interfaces have been observed. Previously, the wustite-spinel interface had been observed to facet on {111} planes for MgFe2C4 and along {100} planes for MgAl2C4 and MgCr2O4, the spinel then grows preferentially in the <001> direction. Reasons for these experimental observations have been discussed by Henriksen and Kingery by considering the strain energy. The point-defect chemistry of such solid state reactions has been examined by Schmalzried. Although MgO has been the principal matrix material examined, others such as NiO have also been studied.

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