Oxidation and intergranular disintegration of the aluminides NiAl and NbAl sub 3 and phases in the system Nb-Ni-Al

Journal Article · Mon Apr 01 00:00:00 EST 1991 · Oxidation of Metals; (United States)

DOI:https://doi.org/10.1007/BF00738286· OSTI ID:6024691

Grabke, H J; Steinhorst, M; Brumm, M; Wiemer, D ^[1]

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1. Max-Planck-Inst. fuer Eisenforschung GmbH, Duesseldorf (West Germany)

The oxidation behavior is very different for an aluminide with a wide homogeneity range such as {beta}-NiAl than for a line compound such as NbAl{sub 3}. Oxidation of {beta}-NiAl at temperatures {ge}1,273 K leads to a slow-growing {alpha}-alumina layer. The metal phase beneath the scale remains as {beta}-NiAl; however, cavity formation is observed. The cavity formation may be favored by sulphur surface segregation. Oxidation of NbAl{sub 3} at temperatures {ge}1,273 K initially leads to {alpha}-Al{sub 2}O{sub 3}, but the Al depletion causes the formation of Nb{sub 2}Al beneath the oxide layer. Cracking of the Al{sub 2}O{sub 3} layer opens Nb{sub 2}Al to the atmosphere, which oxidizes rapidly to Nb{sub 2}O{sub 5} and NbAlO{sub 4}. After consumption of the Nb{sub 2}Al, a layer of Al{sub 2}O{sub 3} formed again on the NbAl{sub 3} phase, but failure of the alumina and the fast growth of the other oxides occur as a repeated process. Thus, NbAl{sub 3} exhibited rapid linear oxidation kinetics. Multiphase alloys in the system Nb-Ni-Al generally behave better than NbAl{sub 3}, and the low oxidation rates of {beta}-NiAl can be approached. In the temperature range below 1,273 K, with a maximum at 1,000 K, both NiAl and NbAl{sub 3} show the pest phenomenon, an intergranular disintegration. Preceding the disintegration, oxygen diffuses into the grain boundaries of the material and Al{sub 2}O{sub 3} is formed at the grain boundaries, beginning from the surface region. NiAl is susceptible only in a very limited range of oxygen pressures and temperatures, whereas NbAl{sub 3} is much more susceptible.

• OSTI ID: 6024691
• Journal Information: Oxidation of Metals; (United States), Vol. 35:3-4; ISSN 0030-770X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
OXIDATION
PHASE STUDIES
NICKEL BASE ALLOYS
NIOBIUM BASE ALLOYS
ALUMINIUM OXIDES
AUGER ELECTRON SPECTROSCOPY
BINARY ALLOY SYSTEMS
CHEMICAL COMPOSITION
CHEMICAL REACTION KINETICS
CRACKS
DIFFUSION
EXPERIMENTAL DATA
GRAIN BOUNDARIES
INTERGRANULAR CORROSION
INTERMETALLIC COMPOUNDS
LAYERS
OXYGEN
SCANNING ELECTRON MICROSCOPY
TERNARY ALLOY SYSTEMS
VERY HIGH TEMPERATURE
ALLOY SYSTEMS
ALLOYS
ALUMINIUM COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
CORROSION
CRYSTAL STRUCTURE
DATA
ELECTRON MICROSCOPY
ELECTRON SPECTROSCOPY
ELEMENTS
INFORMATION
KINETICS
MICROSCOPY
MICROSTRUCTURE
NICKEL ALLOYS
NIOBIUM ALLOYS
NONMETALS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
REACTION KINETICS
SPECTROSCOPY
360105* - Metals & Alloys- Corrosion & Erosion
360102 - Metals & Alloys- Structure & Phase Studies