The effect of reactive elements on the segregation behavior and microstructure of {alpha}-Al{sub 2}O{sub 3} scales on {beta}-NiAl

Conference · Wed Jun 01 04:00:00 EDT 1994

OSTI ID:10155792

Alexander, K B; Pint, B A

In order to improve oxidation resistance, small amounts of oxygen- active or ``reactive`` elements (RE) such as Y, Zr, Hf, Ce are added to chromia- and alumina-forming high-temperature alloys. As an alternative to a system where the RE-ion supply is self-limiting (Y-implant), it was desired to study effect of RE source-removal on microstructure and grain boundary segregation levels. {beta}-NiAl doped with 0.23 wt% Zr was oxidized in oxygen at 1500 C for 50 h. Upon cooling, the scale spalled into pieces; these spalled {alpha}-Al{sub 2}O{sub 3} scales were then annealed in air at 1500 C for 1 and 50 h. Specimens were fabricated parallel to metal/scale interface, and grain boundary chemistries were determined using X-ray energy dispersive spectrometry. Results show that no qualitative change in microstructural scale or zirconia particle size/density occurs after annealing, which is consistent with the model in which the gas- interface microstructure development depends on a continuous supply of zirconia diffusing from the metal interface towards the gas interface.

• Research Organization: Oak Ridge National Lab., TN (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 10155792
• Report Number(s): CONF-940753--10; ON: DE94012739
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360105
ALUMINIUM ALLOYS
ALUMINIUM OXIDES
ANNEALING
CORROSION AND EROSION
CORROSION RESISTANCE
DOPED MATERIALS
INTERFACES
INTERMETALLIC COMPOUNDS
KINETICS
MICROSTRUCTURE
NICKEL ALLOYS
OXIDATION
SCALING
TEMPERATURE RANGE 1000-4000 K
ZIRCONIUM ADDITIONS