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The Oxidation of Ni and Ni-20Cr Deposited with Chromia Thin Films VIA Combustion CVD

Published online by Cambridge University Press:  10 February 2011

A. E. Alexiou ,
M. R. Hendrick  and
J. M. Hampikian
A. E. Alexiou
Affiliation:
School of Materials Science and Engineering Georgia Institute of Technology, Atlanta, GA 30332-0245 U.S.A.
M. R. Hendrick
Affiliation:
MicroCoating Technologies, Inc., 3901 Green Industrial Way, Chamblee, GA 30341, U.S.A
J. M. Hampikian
Affiliation:
Corresponding author
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Abstract

Chromia thin films were deposited onto substrates of Ni and Ni-20Cr by gaseous fuel combustion chemical vapor deposition. The chemical precursor utilized to achieve chromia films was aqueous 0.27M chromium nitrate, and the depositions took place within the flame at temperatures between 200 and 550°C. Amorphous coatings were deposited between 200 and 375°C, whereas crystalline coatings of chromia (eskolaite) were deposited between 400 and 550°C. The eskolaite deposition rate was approximately five times faster than the amorphous chromia. Chromia coatings containing 2 wt% yttria were also formed. The deposition temperature necessary to form crystalline chromia/yttria coatings was slightly higher (∼50°C) than those containing chromia only. The ability of the various coatings to provide oxidation protection was characterized using thermogravimetric analysis (TGA). The eskolaite coatings that are at least 1 im thick reduce the oxidation mass gain/area of Ni-20Cr by nearly a factor of ten and the parabolic constant by an order of magnitude, whereas the amorphous chromia coatings that are 0.6 μm thick do not demonstrate such an improvement. Yttria-doped chromia coatings further reduce the parabolic constant by two orders of magnitude, consistent with expectation. Characterization of the coatings was accomplished using a variety of techniques, including SEM, TEM, EDS, and XRD.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 555: Symposium OO – Properties and Processing of Vapor-Deposited Coatings , 1998 , 67
Copyright
Copyright © Materials Research Society 1999

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