Service limitations for oxidation resistant intermetallic compounds
- NASA Lewis Research Center, Cleveland, OH (United States)
Oxidation resistant intermetallic compounds based on NiAl, TiAl, and MoSi{sub 2} are of interest for high temperature applications. Each system exhibits different life-limiting degradation modes due to oxidation. {beta}-NiAl forms protective {alpha}-Al{sub 2}O scales. Breakdown follows well-established diffusion controlled processes resulting in survival for thousands of hours. The effect of thermal cycling and spalling is well established. Ti{sub 3}Al and TiAl compounds form less protective mixed TiO{sub 2} and Al{sub 2}O{sub 3} scales. However at realistic use temperatures (600--800 C), scale growth rates are acceptably low. The critical factor is embrittlement due to interstitial oxygen diffusion over a matter of hours. Solutions based on alloy development and coatings have not been satisfactory. MoSi{sub 2} materials exhibit very low oxidation rates at very high temperatures. However, low temperature (500 C) pest oxidation can be a catastrophic transient effect. Material integrity is a key factor. Fracture occurs because of accelerated growth of non-protective mixed MoO{sub 2}-SiO{sub 2} scales in pores and microcracks.
- OSTI ID:
- 72546
- Report Number(s):
- CONF-941144-; ISBN 1-55899-265-0; TRN: IM9530%%158
- Resource Relation:
- Conference: Fall meeting of the Materials Research Society (MRS), Boston, MA (United States), 28 Nov - 9 Dec 1994; Other Information: PBD: 1995; Related Information: Is Part Of High-temperature ordered intermetallic alloys VI: Part 2. Materials Research Society symposium proceedings Volume 364; Horton, J. [ed.] [Oak Ridge National Lab., Oak Ridge, TN (United States)]; Baker, I. [ed.] [Dartmouth College, Hanover, NH (United States)]; Hanada, Shuji [ed.] [Tohoku Univ., Sendai (Japan)]; Noebe, R.D. [ed.] [NASA Lewis Research Center, Cleveland, OH (United States)]; Schwartz, D.S. [ed.] [McDonnell Douglas Aerospace, St. Louis, MO (United States)]; PB: 760 p.
- Country of Publication:
- United States
- Language:
- English
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