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 °C has been directly visualized using environmental transmission electron microscopy. Independent of Cr concentration, the oxidation initiates via the 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 through the outer oxide. The Cr concentration plays a more critical role in the later stages of the oxidation. A continuous and more protective Cr2O3 sublayer is established for Ni-20at% Cr, while the Cr2O3 sublayer for Ni-10at%Cr is discontinuous for Ni-10at%Cr. Oxidation persists on the lower Cr alloy where NiO whiskers are observed to preferentially nucleate and grow from the NiCr2O4 islands. It is suggested that short-circuit diffusion of Ni occurs along the NiCr2O4 interfaces through the discontinuous Cr2O3 layer in Ni-10at%Cr to facilitate the selective nucleation of NiO whiskers on the NiCr2O4 surfaces. Conversely, the protective nature of the continuous Cr2O3 film in Ni-20at%Cr blocks this short-circuit pathway and prevents the formation of additional NiO on the surface in the early stage oxidation.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1236302
- Report Number(s):
- PNNL-SA-114164; 48670; KP1704020
- Journal Information:
- Scripta Materialia, Vol. 114; ISSN 1359-6462
- Publisher:
- Elsevier
- Country of Publication:
- United States
- Language:
- English
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