Preparation of Ni-Aluminide Surface Layer Containing Hafnium by Molten-Salt Electrodeposition and Cyclic-Oxidation Resistance

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  • Tabata Kazuki
    Department of Materials Science and Engineering, Graduate School of Engineering and Resource Science, Akita University
  • Fujii Hisato
    Department of Materials Science and Engineering, Graduate School of Engineering and Resource Science, Akita University
  • Sato Naka
    Department of Materials Science and Engineering, Graduate School of Engineering and Resource Science, Akita University
  • Hara Motoi
    Department of Materials Science and Engineering, Graduate School of Engineering and Resource Science, Akita University

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Abstract

The preparation of a coating consisting of Ni aluminide containing a small amount of Hf was carried out by the electrodeposition of Ni using an aqueous solution and the electrodeposition of Hf and Al using a molten salt. Furthermore, in order to change the depth of the layer containing Hf in the coating, a four-step electrodeposition of Ni, Hf, Ni and Al was carried out, and the times of the first and third Ni electrodepositions were changed. As a result, coatings consisting of Ni aluminide, which contained different depths of the Hf-containig layer, were formed. The cyclic-oxidation resistance of these specimens was evaluated in air at 1423 K. For the specimen with a shallow Hf-containing layer in the coating, the specimen mass reduction due to spallation of the scale was observed, whereas for the specimen with a deep Hf-containing layer, the specimen mass reduction was only slightly observed and a high-cyclic oxidation resistance was obtained. Among the specimens with a deep Hf-containing layer, the specimen prepared by Hf deposition for 0.6 ks showed the highest cyclic-oxidation resistance. For this specimen, the scale formed on the coating after the oxidation test consisted of Al2O3. This scale was adhesive, and locally entered the metal substrate.

Journal

  • MATERIALS TRANSACTIONS

    MATERIALS TRANSACTIONS 55 (8), 1311-1318, 2014

    The Japan Institute of Metals and Materials

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