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Diffusion barrier development for fiber-reinforced Ni3Al composites

Published online by Cambridge University Press:  31 January 2011

P.C. Brennan
Affiliation:
Materials Sciences Laboratory, The Aerospace Corporation, El Segundo, California 90245
W.H. Kao
Affiliation:
Materials Sciences Laboratory, The Aerospace Corporation, El Segundo, California 90245
H.A. Katzman
Affiliation:
Materials Sciences Laboratory, The Aerospace Corporation, El Segundo, California 90245
J-M. Yang
Affiliation:
Department of Materials Science and Engineering, University of California, Los Angeles, California 90024
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Abstract

An alumina (Al2O3) diffusion barrier coating to inhibit the interfacial reactions between boron-carbide-coated boron (B4C/B) fibers and a nickel-aluminide (Ni3Al) (IC-221) matrix was investigated. The alumina diffusion barrier was deposited on the B4C/B fibers using chemical vapor deposition. Also, Saphikon single-crystal Al2O3 fibers were used to demonstrate the compatibility between Al2O3 and Ni3Al. The detailed microstructures and chemical compositions of the fibers, coating, and matrix before and after various thermal exposures were analyzed using scanning electron microscopy, energy dispersive x-ray analysis, and ion microprobe mass analysis. The interfacial reaction products present after 6 h at 980 °C were characterized, and Ni was found to be the dominant diffusion species. The alumina diffusion barrier shows promise for effectively inhibiting the deleterious reactions between B4C/B fibers and the Ni3Al matrix. The uncoated B4C/B fibers were consumed by the matrix after fabrication alone, whereas the Al2O3 coated fibers demonstrated resistance to the matrix for 25 h at 880 °C and 6 h at 980 °C. The Saphikon fiber-reinforced Ni3Al composites demonstrated excellent compatibility after 50 h at 1000 °C. Zirconium (Zr)-rich precipitates on the order of 2 μm in diameter formed at the fiber interface after this exposure, but no gross reaction was indicated between the fiber and the matrix.

Type
Articles
Copyright
Copyright © Materials Research Society 1991

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