Anomalous oxidation of intermetallics
- Univ. of Pittsburgh, PA (United States). Dept. of Materials Science and Engineering
MoSi{sub 2}, {beta}-NiAl and TiAl with Cr additions are of interest for high temperature applications in oxidizing environments, where an oxide layer such as SiO{sub 2} or Al{sub 2}O{sub 3} should form to protect the base material. At elevated temperatures (600--1,700 C), a protective SiO{sub 2} layer forms on MoSi{sub 2}, while near 500 C pesting and/or accelerated oxidation could disintegrate the material to powder as Mo and Si oxidize to form a complex, thick, non-protective oxide layer. Use of {gamma}-TiAl is limited by poor oxidation resistance, whereby layered mixed oxides of TiO{sub 2} and Al{sub 2}O{sub 3} form. With the addition of Cr from 4 to 34 at%, results are varied: protective Al{sub 2}O{sub 3} formation, mixed oxide formation as with TiAl or more rapid oxidation than TiAl. NiAl is currently used as a diffusion coating on Ni-based superalloys and is being considered for use as a structural material itself because of its excellent oxidation resistance, i.e. forming {alpha}-alumina above 1,000 C. Recent work indicates that pure NiAl oxidized under low oxygen partial pressures in a contained atmosphere develops nonprotective oxide scales similar to accelerated oxidation of MoSi{sub 2}. This study explores the parameters defining protective behavior of these intermetallics and attempts to describe and explain anomalies at low temperatures and pressures.
- OSTI ID:
- 72547
- Report Number(s):
- CONF-941144-; ISBN 1-55899-265-0; TRN: 95:015628
- 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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