A study was made of void generation, at scale/alloy interfaces during the oxidation of binary alloys, as a result of matter transport through the scale and of diffusion of the alloy components. Various simplifying assumptions were made. In particular, it was assumed that the scale/alloy interface did not move with time and that all of the metal vacancies at the interface condensed there to form voids. This amounted to calculating the maximum rate of interface-void production. The analysis was performed for the case of the parabolic rate law, and for a general kinetic behavior, by using experimental data on the kinetics of weight gain. This treatment was applied to the oxidation of FeAl at 1000C; taking account of the gradual transformation of the initial form of alumina into the stable α form. It predicted the existence of a maximum in the overall void volume; in qualitative agreement with experimental observations. The overall measured volume of voids was much smaller than the calculated values under various conditions. This suggested that an effective mechanism of vacancy annihilation was operating at the scale/alloy interface.

Analysis of Pore Formation at Oxide-Alloy Interfaces – II. Theoretical Treatment of Vacancy Condensation for Immobile Interfaces. F.Gesmundo, P.Y.Hou: Oxidation of Metals, 2003, 59[1-2], 63-81