Abstract
Growth of 
films and scales on 
was investigated in oxygen at 1 atm over the temperature range 1273°–1573°K. An initial sub‐microcrystalline oxide film recrystallized during its growth to a textured 
film containing polycrystalline ridges. Inert marker measurements demonstrated that the initial film grew by inward diffusion of oxygen. Fully developed 
scales contained dissolved nickel (0.5 w/o at 1473°K). Metallographic evidence indicated that these scales grew by counter‐current aluminum and oxygen boundary diffusion and aluminum lattice diffusion. Cavities, which were generated at the 
interface, did not influence scale growth since aluminum was transported at a sufficient sustaining rate by evaporation from the alloy substrate. The square of the average oxide grain size in a growing scale increased proportional to time. The nonparabolic growth kinetics of the 
scales were interpreted by a short‐circuit diffusion model.