The role of Cr in promoting protective alumina scale formation by {gamma}-based Ti-Al-Cr alloys. 1: Compatibility with alumina and oxidation behavior in oxygen

Journal Article · Sun Jun 01 04:00:00 EDT 1997 · Acta Materialia

DOI:https://doi.org/10.1016/S1359-6454(96)00362-X· OSTI ID:514657

Brady, M P; Smialek, J L ^[1]; Smith, J; Humphrey, D L ^[2]

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1. NASA Lewis Research Center, Cleveland, OH (United States)
2. NYMA, Inc., Cleveland, OH (United States). NASA Lewis Group

The substitution of greater than 8--10 at.% Cr for Ti in Ti-Al reduces the level of Al needed for protective alumina scale formation during oxidation, the Cr effect. To elucidate the mechanism of the Cr effect, the interaction of binary Ti-A/l and ternary Ti-Al-Cr alloys with alumina was examined at 1,000 C by hot-pressed diffusion couples. The oxidation behavior of the same alloys was also examined at 1,000 C in dry oxygen. The dissolution of alumina in an alloy/alumina diffusion couple correlated with an inability of the alloy to form a protective alumina scale on exposure in dry oxygen because of internal attack. Both of these effects were associated with high oxygen permeability in the alloy. It was postulated that the Cr effect results from the Ti(Cr,Al){sub 2} Laves phase, which has a low oxygen permeability and is capable of alumina scale formation despite its relatively low Al content of 37--42 at.% Al.

• Sponsoring Organization: National Aeronautics and Space Administration, Washington, DC (United States)
• OSTI ID: 514657
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Journal Issue: 6 Vol. 45; ISSN 1359-6454; ISSN ACMAFD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
ALUMINIUM OXIDES
CHROMIUM
CHROMIUM ALLOYS
DISSOLUTION
LAVES PHASES
METALLURGICAL EFFECTS
OXIDATION
PASSIVATION
PROTECTIVE COATINGS
TITANIUM ALLOYS