Coating of Ni-Al intermetallic compound on Nb by electrodeposition treatment and high temperature oxidation resistance

The coating of a Ni aluminide layer on a Nb substrate was carried out by the electrodeposition of Ni and Al. The improvement of the high-temperature oxidation resistance for Nb was then evaluated. Ni and Al were deposited by aqueous solution and molten salt electrolysis, respectively. The thickness of the deposited layer increased with time for the nickel electrodeposition. When the nickel electrodeposition time is short, NiAl3 and Ni2Al3 are formed as the outer and inner layers, respectively. When the nickel electrodeposition time becomes longer, on the other hand, Ni2Al3 and Ni are formed as the outer and inner layers, respectively. The oxidation resistance of Nb was improved by coating of the Ni-aluminum intermetallic compound. Especially, a Nb specimen covered with a coating layer consisting of Ni2Al3 and Ni as the outer and inner layers, respectively, showed an improved oxidation resistance during the prolonged oxidation test.