MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
The Oxide Scale Formation and Evolution on Detonation Gun Sprayed NiCrAlY Coatings during Isothermal Oxidation
Zhaoxiang ChenFuhe YuanZhongguang WangShijie Zhu
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2007 Volume 48 Issue 10 Pages 2695-2702

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Abstract

NiCrAlY coatings were prepared by the newly-developed detonation gun spray process. The oxide scale formation and evolution on these coatings during isothermal oxidation in air at 1100°C were investigated. It was found that semi-molten particles, particle debris and pores, are present in the surface layer of the as-sprayed coating. During 100 h oxidation, the particle debris and some semi-molten particles gradually change into oxide mixture consisting of spinel, chromia and nickel oxides. However, after removal of the surface layer of the coating by a grinding treatment, a dense and single-layer α-Al2O3 scale forms on the surface of the coating during the oxidation. The mechanisms governing the oxide scale formation and evolution are discussed in terms of atomic diffusion and thermodynamic stability. In addition, thermogravimetric analysis showed that the oxidation rate of the ground NiCrAlY coating at 1100°C is much lower than that of the as-sprayed one. The residual stress in thermally grown oxide scales was investigated using photo-stimulated luminescence spectroscopy.

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© 2007 The Japan Institute of Metals and Materials
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