Abstract
Results of structural studies performed with light microscopy, SEM, TEM, and EDXS on NiCrAlY coating as-plasma sprayed in air are presented in this paper. The internal structure of the coating was found to be a heterogeneous mixture of matrix metal, non-molten powders, and oxide inclusions. The microstructure of the matrix metal consists of γ-Ni, β-NiAl, and martensitic NiAl grains with Y bound in the Ni₅Y yttride located in the grain boundary regions. All the basically aluminium base oxide inclusions were determined as amorphous structures. Fine-grained structure of the coating, dramatic increase of hardness, and the amorphous structure of the oxides are assumed to be the results of extremely high cooling rates of molten powders after their impingement on the substrate.

Key words
NiCrAlY coating as-plasma sprayed, structural studies, SEM, TEM, and EDXS

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