Grain Boundary Chemistry and Transport Through Alumina Scales on NiAl Alloys
Artikel i vetenskaplig tidskrift, 2017

It is widely accepted that the growth of protective ?-Al2O3 scales on Ni-based alloys is governed by the inward diffusion of oxygen through the oxide grain boundaries (GB). However, there is also some outward diffusion of metal ions to the surface, but it is difficult to quantify. In this work we apply atomic force microscopy, scanning electron microscopy and transmission electron microscopy to investigate the outward flux of Al, which manifests as the growth of small ridges along the alumina GBs after the removal of the outermost oxide layer by mechanical polishing or focused ion beam techniques followed by additional oxidation. As a model alumina-former, NiAl with Hf and Zr additions was investigated. In comparison to Zr, Hf was found to reduce the outward Al diffusion. This outward diffusion was six orders of magnitude smaller than the O inward diffusion.

Diffusion

Oxidation

Reactive elements

Grain boundaries

Atom probe tomography

Författare

Torben Boll

Chalmers, Fysik, Biologisk fysik

K.A. Unocic

Oak Ridge National Laboratory

B.A. Pint

Oak Ridge National Laboratory

Anders Mårtensson

Chalmers, Kemi och kemiteknik, Tillämpad kemi, Polymerteknologi

Krystyna Marta Stiller

Chalmers, Fysik, Biologisk fysik

Oxidation of Metals

0030-770X (ISSN) 1573-4889 (eISSN)

Vol. 88 3-4 469-479

Ämneskategorier

Materialkemi

DOI

10.1007/s11085-016-9697-x