Service limitations for oxidation resistant intermetallic compounds

Conference · Sat Jul 01 04:00:00 EDT 1995

OSTI ID:72546

Smialek, J L; Nesbitt, J A; Brindley, W J; Brady, M P; Doychak, J; Dickerson, R M; Hull, D R ^[1]

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1. 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
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
ALUMINIUM OXIDES
CORROSION PRODUCTS
CORROSION RESISTANCE
HEAT RESISTING ALLOYS
INTERMETALLIC COMPOUNDS
MOLYBDENUM SILICIDES
NICKEL ALLOYS
OXIDATION
SCALING
TITANIUM ALLOYS
TITANIUM OXIDES