Formation of Ni Aluminide Containing Hf by Simultaneous Electrodeposition of Al and Hf and Cyclic-Oxidation Resistance

抄録

A Ni aluminide layer containing Hf was formed on a Ni specimen by the simultaneous electrodeposition of Al and Hf using a molten-salt bath. Al and Hf were only slightly electrodeposited and an electrodeposited layer was not formed when the simultaneous electrodeposition of Al and Hf was tried using molten NaCl-KCl containing 3.5 mol%AlF₃ and 3.5 mol%HfF₄. On the other hand, an electrodeposited layer consisting of Ni₂Al₃ and NiAl₃ layers, for which the Al₃Hf particles were formed on the surface region, was formed, when the simultaneous electrodeposition of Al and Hf was carried out using the molten NaCl-KCl containing 3.5 mol% AlF₃ and 0.05 mol% HfF₄. The cyclic-oxidation resistance of the Ni specimens covered by the Ni aluminide layer containing the Al₃Hf particles was evaluated in air at 1423 K. The sample covered with the Ni aluminide containing the Al₃Hf particles, which was formed using the melt containing 3.5 mol%AlF₃ and 0.05 mol%HfF₄, showed a high cyclic-oxidation resistance. On this sample after the oxidation test, an adhesive scale having a spiked shape, which consisted of Al₂O₃ as the outer layer and HfO₂ as the inner layer, was formed.