Microstructural evolution of duplex grain structure and interpretation of the mechanism for NiO scales grown on pure Ni- and Cr-doped substrates during high temperature oxidation

Duplex layers are a very important class of film microstructures and form under a wide variety of processing conditions such as oxidation (sulfidation), sputtering, evaporation and casting on a large number of substrates. In this paper, the available models for duplex layer formation are criticized in detail and the basic assumptions which are based upon them are examined. Then, mechanisms of formation of the duplex layers based on microstructural observations in pure Ni and Ni–1at% Cr systems during high temperature oxidation are addressed.