日本金属学会誌

J. Japan Inst. Metals, Vol. 69, No. 8 (2005),
pp. 695-698

Formation of Ni Aluminide Surface Layer Containing La by Molten-Salt Electrodeposition and Cyclic-Oxidation Resistance

Michihisa Fukumoto1, Motoi Hara1 and Toshio Narita2

1Department of Materials Science and Engineering, Faculty of Engineering and Resource Science, Akita University, Akita 010-8502
2Division of Materials Science and Engineering, Reserch Group of Energy Materials, Laboratory of Advanced High Temperature Materials, Hokkaido University, Sapporo 060-8628

Abstract:

In order to improve the cyclic-oxidation resistance of Ni, the coating of a Ni aluminide containing La on the Ni was carried out by the electrodeposition of Al and La in a molten salt. The electrodepositions of Al and La were conducted using a potentiostatic polarization method at 1023 K in an equimolar NaCl-KCl melt containing 3.5 mol%AlF3 and that containing 4 mol%La2O3 and 24 mol%NH4Cl, respectively. Observation and analysis of the cross-section of the specimen after polarization showed that a deposit layer consisting of a thick inner Ni aluminide layer and a thin outer layer containing a large amount of La was formed on the Ni specimen. The cyclic-oxidation resistance of the specimen coated with the deposit layer having the layer containing La as an outer layer was higher than those of the untreated Ni specimen and the specimen coated with deposit layer without La. The scale formed on the specimen coated with the deposit layer without La after the oxidation test was thick and consisted of NiO, whereas the scale formed on the specimen coated with the deposit layer having the layer containing La was extremely thin, and consisted of α-Al2O3.


(Received 2005/4/25)

Keywords:

electrodeposition, molten salt, Lanthanum, aluminum, high-temperature oxidation, nickel aluminide, coating


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