Isothermal oxidation behavior of alpha-2 titanium aluminide alloys. [Ti-25Al-10Nb-3V-1Mo and Ti-24. 5Al-12. 5Nb-1. 5Mo]

Journal Article · Thu Apr 01 00:00:00 EST 1993 · Scripta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-716X(93)90354-U· OSTI ID:6612978

Schaeffer, J C ^[1]

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1. GE Aircraft Engines, Cincinnati, OH (United States)

Monolithic alpha-2 alloys are being considered for applications in gas turbine engines at temperature between 593 and 705C. The alpha-2 alloys have better creep and oxidation resistance than conventional Ti alloys in this temperature range, but concerns over low temperature mechanical properties, interstitial embrittlement and hot salt stress corrosion cracking have limited the application of these alloys. Protective coatings address environmental concerns, while improved processing and chemistry may improve mechanical properties. The compositions of alpha-2 alloys have evolved over time to obtain a better balance of properties. Two prospective alpha-2 compositions are Ti-25Al-10Nb-3V-1Mo and Ti-24.5Al-12.5Nb-1.5Mo. This work characterizes the isothermal oxidation behavior of these two alloys in the 593-705C temperature range and discusses observed differences. The isothermal oxidation behavior in air of Ti-24.5Al-12.5Nb-1.5Mo was superior to Ti-25Al-10Nb-3V-1Mo and T-6242 in the temperature range of 593-705C. The 12.5-1.5 alloy was better because an external alumina scale formed which grew more slowly than the TiO[sub 2]-based scales observed on the 10-3-1 and Ti-6242. The alumina scale formed on the 12.5-1.5 alloy because interstitials like O, N and C lower the thermodynamic activity of Ti to levels where Al[sub 2]O[sub 3] formation is favored. In the absence of microstructural effects, the V in 10-3-1 prevented continuous external alumina from forming.

• OSTI ID: 6612978
• Journal Information: Scripta Metallurgica et Materialia; (United States), Vol. 28:7; ISSN 0956-716X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
OXIDATION
MOLYBDENUM ALLOYS
NIOBIUM ALLOYS
TITANIUM BASE ALLOYS
VANADIUM ALLOYS
ALUMINIUM OXIDES
EXPERIMENTAL DATA
GAS TURBINE ENGINES
INTERSTITIALS
SCALING
TEMPERATURE RANGE 0400-1000 K
ALLOYS
ALUMINIUM COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DATA
ENGINES
HEAT ENGINES
INFORMATION
INTERNAL COMBUSTION ENGINES
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
POINT DEFECTS
TEMPERATURE RANGE
TITANIUM ALLOYS
360105* - Metals & Alloys- Corrosion & Erosion