THE STRUCTURAL-KINETIC INVESTIGATION OF THE PROCESS OF OXIDATION OF NICKEL, CHROME, AND ALLOYS BASED UPON THEM
FOREIGN TECHNOLOGY DIV WRIGHT-PATTERSON AFB OH
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The speed of oxidization of a binary alloy containing 80 Ni and 20 Cr is less than the speed of oxidization of chrome at temperatures of 800 - 1000C. The oxide films originating on this alloy consist at 400C of oxide of nickel Ni0 at 500 - 700C they consist of oxide of chrome alpha - Cr203 at 800 - 1000C - of two layers of various compositions. The surface layer of the oxide film consists of an oxide of the spinel type NiCr204. That of the inside layer consists of oxide of chrome alpha - Cr203. The speed of oxidization of the nickel-chrome alloy decreases with additions of aluminum. For a satisfactory protection of the alloy Ni-Cr from oxidization up to a temperature of 900C an aluminum content in a quantity of 4 - 5 suffices and at 1000C, 7 suffices. Oxide films forming on alloys with 1 of aluminum with 4. 18 A1, 7.22 A1, and 10 A1 at 400C, consist of oxide films of Ni0 at 500 - 600C, they consist of oxide of chrome alpha - Cr204 at 700 - 1000C, they consist of solid solutions of oxides of the spinel type, NiCr204, NiA1204, and gamma - A1203. Oxide of aluminum is concentrated in the inner layers of the oxide film. Slight additions of titanium 0.68 decrease the speed of oxidization of the Ni-Cr alloy and large additions increase it. The process of oxidization of the given alloys is principally caused by the diffusion of the ions of the metals.
- Physical Chemistry
- Properties of Metals and Alloys