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The Use of Fluorine to Protect β-Solidifying γ-TiAl-Based Alloys against High-Temperature Oxidation

Published online by Cambridge University Press:  13 February 2017

Alexander Donchev ,
Mathias Galetz ,
Svea Mayer ,
Helmut Clemens  and
Michael Schütze
Alexander Donchev*
Affiliation:
DECHEMA-Forschungsinstitut Theodor-Heuss-Allee 25 D-60486 Frankfurt am Main/Germany
Mathias Galetz
Affiliation:
DECHEMA-Forschungsinstitut Theodor-Heuss-Allee 25 D-60486 Frankfurt am Main/Germany
Svea Mayer
Affiliation:
Department of Physical Metallurgy and Materials Testing Montanuniversität Leoben Roseggerstr. 12 A-8700 Leoben/Austria
Helmut Clemens
Affiliation:
Department of Physical Metallurgy and Materials Testing Montanuniversität Leoben Roseggerstr. 12 A-8700 Leoben/Austria
Michael Schütze
Affiliation:
DECHEMA-Forschungsinstitut Theodor-Heuss-Allee 25 D-60486 Frankfurt am Main/Germany
*
*(Email: [email protected])
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Abstract

Light-weight alloys based on intermetallic titanium aluminides (TiAl) are structural materials considered for high-temperature applications, e.g. in aero engines or automotive engines. TiAl alloys of engineering interest consist of two phases, the γ-TiAl and the α2-Ti3Al-phase. Recent developments have led to the so-called TNM alloys (T = TiAl; N = Nb; M = Mo) with an Al-content of 43.5 at.%. These alloys also possess the disordered body centered cubic β-Ti(Al)-phase at elevated temperatures, which ensures a better hot-workability compared to conventional two-phase alloys. However, the relatively low Al content (< 45 at.%) limits the high-temperature capability due to reduced oxidation resistance. This impedes their application in a temperature range above 800°C. The present work shows how the fluorine effect counteracts this disadvantage due to the formation of a protective alumina layer. The performance of the TNM alloy with the nominal composition of Ti-43.5Al-4Nb-1Mo-0.1B (at.%) is compared with another TNM alloy variant containing additional elements, such as Si and C, and the so-called GE alloy (Ti-48Al-2Cr-2Nb; at.%), which is already in use for turbine blades. The results of isothermal and thermocyclic high-temperature exposure tests of untreated and fluorine treated specimens will be compared. The effect of composition and microstructure of the alloys on the oxidation behavior with and without fluorine treatment are discussed.

Keywords

oxidationelectron microprobealloy
Type
Articles
Information
MRS Advances , Volume 2 , Issue 25: Mechanical Behavior and Failure Mechanisms of Materials , 2017 , pp. 1361 - 1367
Copyright
Copyright © Materials Research Society 2017 

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References

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