Initial Aluminizing Steps of Pure Nickel from Al Micro-Particles

Abstract:

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Novel, unconventional type of high temperature coating systems can be elaborated by depositing Al micro-particles on nickel base substrates, using an appropriate binder, and converting them into a thermal barrier type coating by a two-step heat treatment under argon. Final result is a coating structure consisting of a quasi-foam top coat, constituted by spherical hollow alumina particles, surmounting a β-NiAl diffusion layer able to form during high-temperature oxidation a protective alumina scale. In this work, pure nickel was employed as a model material to evaluate the effects of moderate temperatures (550-700°C), dwelling times and Al particle size on the final characteristics of the coatings. Almost no diffusion occurred below 600°C. In contrast, a Ni2Al3 layer very quickly formed at 650 or 700°C. The rapidity of coating formation was attributed to the appearance of a liquid phase at the coating/substrate interface. The increase of dwelling time did not provide any significant thickness increase as the Al particles got practically emptied after 2h. In addition, the use of different micro-sized particles resulted in similar Al diffusion coatings under the investigated conditions.

Info:

Periodical:

Defect and Diffusion Forum (Volumes 323-325)

Edited by:

I. Bezverkhyy, S. Chevalier and O. Politano

Pages:

381-386

Citation:

G. Bonnet et al., "Initial Aluminizing Steps of Pure Nickel from Al Micro-Particles", Defect and Diffusion Forum, Vols. 323-325, pp. 381-386, 2012

Online since:

April 2012

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$38.00

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