Reaction synthesis of Ni-Al-based particle composite coatings |
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Authors: | D F Susan W Z Misiolek A R Marder |
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Affiliation: | (1) Present address: Materials Science and Engineering Department, Lehigh University, USA;(2) Materials Characterization Department, Sandia National Laboratory, 87185 Albuquerque, NM;(3) the Materials Science and Engineering Department, Lehigh University, 18015 Bethlehem, PA |
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Abstract: | Electrodeposited metal matrix/metal particle composite (EMMC) coatings were produced with a nickel matrix and aluminum particles.
By optimizing the process parameters, coatings were deposited with 20 vol pct aluminum particles. Coating morphology and composition
were characterized using light optical microscopy (LOM), scanning electron microscopy (SEM), and electron probe microanalysis
(EPMA). Differential thermal analysis (DTA) was employed to study reactive phase formation. The effect of heat treatment on
coating phase formation was studied in the temperature range 415 °C to 1000 °C. Long-time exposure at low temperature results
in the formation of several intermetallic phases at the Ni matrix/Al particle interfaces and concentrically around the original
Al particles. Upon heating to the 500 °C to 600 °C range, the aluminum particles react with the nickel matrix to form NiAl
islands within the Ni matrix. When exposed to higher temperatures (600 °C to 1000 °C), diffusional reaction between NiAl and
nickel produces (γ′)Ni3Al. The final equilibrium microstructure consists of blocks of (γ′)Ni3Al in a γ(Ni) solid solution matrix, with small pores also present. Pore formation is explained based on local density changes during
intermetallic phase formation, and microstructural development is discussed with reference to reaction synthesis of bulk nickel
aluminides. |
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