In-situ transmission electron microscopy study of surface oxidation for Ni-10Cr and Ni-20Cr alloys

The early-stage oxidation of Ni (001) thin films alloyed with 10 or 20 at.% Cr at 700 degrees C has been directly visualized using in-situ TEM. Independent of Cr concentration, the oxidation initiates via nucleation of surface NiO islands and subsurface Cr2O3. The NiO grows and transitions into a continuous film, followed by the nucleation and growth of NiCr2O4 islands. For Ni-20 at.% Cr, a continuous Cr2O3 was developed, but not for Ni-10 at.% Cr. NiO whiskers are observed to preferentially nucleate/grow from the NiCr2O4 islands through a short-circuit diffusion of Ni along the NiCr2O4 interfaces in Ni-10 at.% Cr. (C) 2015 Scripta Materialia. Published by ELSEVIER Ltd. All rights reserved.