Effects of an α-Al2O3 thin film on the oxidation behavior of a single-crystal Ni-based superalloy

Y. F. Su; L. F. Allard; D. W. Coffey; W. Y. Lee

doi:10.1007/s11661-004-1008-5

Effects of an α-Al₂O₃ thin film on the oxidation behavior of a single-crystal Ni-based superalloy

Y. F. Su, L. F. Allard, D. W. Coffey, W. Y. Lee

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15 Scopus citations

Abstract

A ~ 150-nm-thick coating layer consisting of α-Al₂O ₃ as the major phase with a minute amount of θ-Al ₂O₃ was deposited on the surface of a single-crystal Ni-based superalloy by chemical vapor deposition (CVD). Within 0.5 hours of oxidation at 1150 °C, the resulting thermally grown oxide (TGO) formed on the coated alloy surface underwent significant lateral grain growth. Consequently, within this time scale, the columnar nature of the TGO became established. After 50 hours, a network of ridges was clearly observed on the TGO surface instead of equiaxed grains typically observed on the uncoated alloy surface. Comparison of the TGO morphologies observed with and without the CVD-Al₂O₃ layer suggested that the transient oxidation of the alloy surface was considerably reduced. Also, the CVD-Al₂O ₃ layer significantly reduced the growth rate of the TGO and improved its spallation resistance, while slowing the internal oxidation of Ta-rich areas that were present in the superalloy as-casting defects. These results demonstrated that this thin α-Al₂O₃ coating could be used as a means of favorably altering the TGO morphology and growth kinetics for no bond coat thermal barrier coating (TBC) applications.

Original language	English
Pages (from-to)	1055-1065
Number of pages	11
Journal	Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
Volume	35
Issue number	13
DOIs	https://doi.org/10.1007/s11661-004-1008-5
State	Published - 2004
Externally published	Yes

Funding

This research was sponsored by the United States Office of Naval Research (ONR) through Grant No. N00014-99-1-0281. We are grateful to Dr. Steven Fishman, ONR, for his support and encouragement. The FIB and high-resolution TEM studies performed at ORNL were sponsored by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Transportation Technologies, as part of the High Temperature Materials Laboratory User Program, Oak Ridge National Laboratory, managed by UT–Battelle LLC for the United States Department of Energy under Contract No. DE-AC05-00OR22725. We also thank Professor Henry Du for the use of his oxidation furnaces and for his insightful comments during our investigation.

Funders	Funder number
Battelle LLC
Office of Transportation Technologies
Secretary for Energy Efficiency and Renewable Energy
Office of Naval Research	N00014-99-1-0281
U.S. Department of Energy	DE-AC05-00OR22725
Oak Ridge National Laboratory

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abstract = "A ~ 150-nm-thick coating layer consisting of α-Al2O 3 as the major phase with a minute amount of θ-Al 2O3 was deposited on the surface of a single-crystal Ni-based superalloy by chemical vapor deposition (CVD). Within 0.5 hours of oxidation at 1150 °C, the resulting thermally grown oxide (TGO) formed on the coated alloy surface underwent significant lateral grain growth. Consequently, within this time scale, the columnar nature of the TGO became established. After 50 hours, a network of ridges was clearly observed on the TGO surface instead of equiaxed grains typically observed on the uncoated alloy surface. Comparison of the TGO morphologies observed with and without the CVD-Al2O3 layer suggested that the transient oxidation of the alloy surface was considerably reduced. Also, the CVD-Al2O 3 layer significantly reduced the growth rate of the TGO and improved its spallation resistance, while slowing the internal oxidation of Ta-rich areas that were present in the superalloy as-casting defects. These results demonstrated that this thin α-Al2O3 coating could be used as a means of favorably altering the TGO morphology and growth kinetics for no bond coat thermal barrier coating (TBC) applications.",

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Effects of an α-Al₂O₃ thin film on the oxidation behavior of a single-crystal Ni-based superalloy

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