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An investigation of bond formation between alumina single crystals and nickel alloys Clarke, John Frank

Abstract

An investigation was conducted on the mechanisms of bond formation between alloys of nickel and single crystals of alumina. Nickel-titanium, nickel-chromium, and nickel-zirconium powder mixtures were cleaned with purified hydrogen gas at 800°C and were individually melted under vacuum (10⁻⁵ m.m. of Hg) in contact with alumina. Interfacial energy measurements at 1500°C were made by the sessile-drop method. The bond surfaces were examined by X-ray fluorescence and X-ray diffraction techniques. The bond formation in all cases appeared to involve two basic mechanisms - metal solute segregation and interfacial reaction. By interfacial measurements and X-ray fluorescence analyses, the solute atoms, titanium and chromium, were shown to be selectively adsorbed at the metal-ceramic interface. Interfacial reaction products were detected by X-ray diffraction methods. The adsorbed titanium reacted with the alumina to produce an interfacial layer of alpha titanium sesqui oxide (⍺-Ti₂0₃). Adsorbed chromium similarly reacted with the alumina to form an interfacial compound. However, this compound could not be identified. With nickel-zirconium alloys, the violence of the reaction between zirconium and alumina made experimental measurements impossible.

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