High temperature oxidation of iron at 1200 °C in a hot-stage environmental scanning electron microscope

Abstract

The growth of a wustite scale on pure iron oxidized at 1200 °C and\(P_{O_2 } \cong 10^{ - 4} \) atm was studied in a hot stage environmental scanning electron microscope. Macroscopic ledges for the growth of wustite were seen to evolve from pits at the oxide/gas interface. These pits are anchored by screw dislocations emerging at the surface, and the sides of pits represent oxide planes of low surface energy. The intermittent activity/inactivity of pits may result from the climb of an edge dislocation jog segment to the surface. The passage of an oxide grain boundary through a pit was observed during wustite grain growth. The particular appearance of growth pits, or else of faceted ledges, on different grains is decided by the relative orientations of the nominal surface plane with the lattice planes of low surface energy.