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Influence of different annealing processes on the oxidation behaviour of γ-TiAl

Ebach-Stahl, Andrea und Fröhlich, Maik und Leyens, Christoph (2008) Influence of different annealing processes on the oxidation behaviour of γ-TiAl. 7th International Conference on Microscopy of Oxidation, 2008-09-15 - 2008-09-17, Chester, UK.

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Kurzfassung

Titanium aluminides are an attractive material for aerospace as well as automotive industry particularly due to their low mass density and good mechanical properties in the temperature range between 700°C and 900°C. But above 750°C titanium aluminides show a poor oxidation behaviour caused by fast growing titania. In this study particularly thermally pre-treated γ-TiAl was investigated with regard to the oxidation resistance in comparison to non pre-treated material. The Ti-45Al-8Nb alloy was exposed under various conditions, such as different atmospheres (high vacuum, Ar- and H<sub>2</sub>-atmosphere), temperature (900°C and 1000°C) and time (1-200h). Under high vacuum conditions (10<sup>-6</sup>mbar) only phase transformation in the surface region took place. The lamellar structure of the base material changed into single α<sub>2</sub>-Ti<sub>3</sub>Al with oxygen enrichment on top. Under Ar-atmosphere (50mbar) mainly nitrides were formed at the surface with an α<sub>2</sub>-layer and σ-Nb<sub>2</sub>Al precipitations below. During annealing γ-TiAl in hydrogen under atmospheric pressure (1040mbar) the material oxidized relatively fast. A dense TiO<sub>2</sub> layer was formed on top, followed by a mixed oxide scale and a relatively thick region of alumina and σ-Nb<sub>2</sub>Al precipitations in an α<sub>2</sub>-Ti<sub>3</sub>Al matrix. Several samples of these various thermally pre-treated materials were tested by cyclic oxidation at 900°C in air for investigating the oxidation behaviour. The microstructures of the formed oxides of pre-treated and non pre-treated γ-TiAl are comparable. The material pre-treated under high vacuum conditions exhibited the lowest oxidation rate, while the mass gain of the specimens annealed under Ar-atmosphere increased rapidly in the first cycles. All pre-treated specimens exceeded a lifetime of 600 cycles at minimum. The reference material showed spallation already after 520 cycles. The microstructure and phase formation of all annealed and tested samples were investigated by SEM and EDX.

elib-URL des Eintrags:https://elib.dlr.de/56459/
Dokumentart:Konferenzbeitrag (Vortrag)
Titel:Influence of different annealing processes on the oxidation behaviour of γ-TiAl
Autoren:
AutorenInstitution oder E-Mail-AdresseAutoren-ORCID-iDORCID Put Code
Ebach-Stahl, AndreaNICHT SPEZIFIZIERTNICHT SPEZIFIZIERTNICHT SPEZIFIZIERT
Fröhlich, MaikNICHT SPEZIFIZIERTNICHT SPEZIFIZIERTNICHT SPEZIFIZIERT
Leyens, ChristophNICHT SPEZIFIZIERTNICHT SPEZIFIZIERTNICHT SPEZIFIZIERT
Datum:17 September 2008
Open Access:Nein
Gold Open Access:Nein
In SCOPUS:Nein
In ISI Web of Science:Nein
Stichwörter:titanium aluminides, vacuum annealing, argon annealing, hydrogen annealing, oxidation behaviour, pre-treatment
Veranstaltungstitel:7th International Conference on Microscopy of Oxidation
Veranstaltungsort:Chester, UK
Veranstaltungsart:internationale Konferenz
Veranstaltungsdatum:2008-09-15 - 2008-09-17
Veranstalter :University of Liverpool, University of Birmingham
HGF - Forschungsbereich:Verkehr und Weltraum (alt)
HGF - Programm:Luftfahrt
HGF - Programmthema:Antriebe (alt)
DLR - Schwerpunkt:Luftfahrt
DLR - Forschungsgebiet:L ER - Antriebsforschung
DLR - Teilgebiet (Projekt, Vorhaben):L - Turbinentechnologien (alt)
Standort: Köln-Porz
Institute & Einrichtungen:Institut für Werkstoff-Forschung > Hochtemperatur-und Funktionsschutzschichten
Hinterlegt von: Ebach-Stahl, Andrea
Hinterlegt am:03 Dez 2008
Letzte Änderung:27 Apr 2009 15:32

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