Investigation of Oxide Film Growth Stresses by Finite Element Modeling and Deflection Tests

Abstract

The strain and the stresses generated by the growth of an oxide film was made using two approaches: an experimental one by means of deflection tests and a modeling one via finite element simulations. NiO growth on nickel was chosen because many microstructural, kinetics and mechanical data were available for this system. It was also compared with experimental and calculated results obtained with NiO growth on a NiCr alloy. The results indicate that the oxide layers are mostly subjected to compressive stresses when NiO is growing, but the stress level and evolution clearly indicate that viscoplastic strain of both the substrate and the oxide occurs during the oxidation, at least at 900-800°C. The oxide stress evolution with the oxidation time is more important with Ni as a substrate than with NiCr, because of the greater stiffness of NiCr. The comparison of experiments and modeling also shows that anisotropic growth of the oxide must be considered to account for the results.