|About this Abstract
||Materials Science & Technology 2012
||Surface Protection for Enhanced Materials Performance: Science, Technology and Applications
||Permeability Studies and Grain-Boundary Diffusion in Alumina Scales
||James L. Smialek, Nathan S. Jacobson, Brian Gleeson, David B. Hovis, Arthur H. Heuer
|On-Site Speaker (Planned)
||James L. Smialek
Recent high temperature permeability measurements have determined grain boundary diffusivities in bulk polycrystalline alumina (Wada, Matsudaira, Kitaoka, 2011) and predict that oxygen boundary diffusion varies with PO2(-1/6) (at metal interface) while aluminum varies with PO2(+3/16)(at gas surface). Coupled with a modified Wagner treatment for dominant oxygen inward growth, a simple relation was obtained where the product of instantaneous kp(i)and grain size equals 1/12 oxygen boundary diffusivity. A commercial FeCrAl(Zr) alloy was oxidized at 1100°-1400°C to determine kp(i), interfacial grain size, and calculation of this oxygen boundary diffusivity. The experimental values were 10-40x less than those predicted by the permeability relations, but closer than extrapolations from typical high temperature measurements in bulk alumina. The experimental results agree with similar oxidation studies in the literature and new kinetic data for Ni(Pt)Al coatings, including TGA, cyclic furnace, and burner rig.