Modeling Two- and Three-Stage Oxygen Tracer Experiments during High-Temperature Oxidation of Metals with a High Oxygen Solubility

Abstract

The numerical tool EKINOX-Zr has been upgraded to simulate oxygen tracer experiments during the high-temperature oxidation of a metal with a high oxygen solubility limit. The penetration of 18O tracer is calculated during the dynamic evolution of the ZrO2-x/$\alpha$Zr(O)/$\beta$zr system. The numerical approach allows to explicitly take into account the variation of the tracer diffusion coefficient through the oxide scale as a function of the vacancy concentration. A classical two-stages 16O2/18O2 tracer experiment has been simulated. It is shown that a classical fitting procedure on the 18O concentration profile obtained for short-time experiments leads to the identification of the oxygen chemical diffusion coefficient. The second type of tracer experiment is proposed using a three-stages 16O2/18O2/16O2 oxidation. It allows the direct estimation of the diffusion coefficient from the transport of 18O peak in the growing oxide scale.