Transient Oxidation of a γ-Ni-28Cr-11Al Alloy

Journal Article · Mon Apr 02 04:00:00 EDT 2012 · Oxidation of Metals

DOI:https://doi.org/10.1007/s11085-009-9179-5· OSTI ID:1036897

Hu, L; Hovis, D B; Heuer, A H ^[1]

---

1. Case Western

γ-NiCrAl alloys with relatively low Al contents tend to form a layered oxide scale during the early stages of oxidation, rather than an exclusive α-A_l2O₃ scale, the so-called 'thermally grown oxide' (TGO). A layered oxide scale was established on a model γ-Ni-28Cr-11Al (at.%) alloy after isothermal oxidation for several minutes at 1100 °C. The layered scale consisted of an NiO layer at the oxide/gas interface, an inner Cr₂O₃ layer, and an α-Al₂O₃ layer at the oxide/alloy interface. The evolution of such an NiO/Cr₂O₃/Al₂O₃ layered structure on this alloy differs from that proposed in earlier work. During heating, a Cr₂O₃ outer layer and a discontinuous inner layer of Al₂O₃ initially formed, with metallic Ni particles dispersed between the two layers. A rapid transformation occurred in the scale shortly after the sample reached maximum temperature (1100°C), when two (possibly coupled) phenomena occurred: (i) the inner transition alumina transformed to α-Al₂O₃, and (ii) Ni particles oxidized to form the outer NiO layer. Subsequently, NiO reacted with Cr₂O₃ and Al₂O₃ to form spinel. Continued growth of the oxide scale and development of the TGO was dominated by growth of the inner α-Al₂O₃ layer.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: U.S. OFFICE OF NAVAL RESEARCH
• OSTI ID: 1036897
• Journal Information: Oxidation of Metals, Journal Name: Oxidation of Metals Journal Issue: (1) ; 2010 Vol. 73; ISSN OXMEAF; ISSN 0030-770X
• Publisher: Springer
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

36 MATERIALS SCIENCE
ALLOYS
HEATING
OPTICAL MICROSCOPY
OXIDATION
OXIDES
TRANSFORMATIONS
TRANSIENTS