Effect of the application of a mechanical load on the oxide-layer microstructure and on the oxidation mechanism of Ni-20Cr foils

The effect of a tensile load on the oxidation kinetics and mechanism of Ni- 20Cr was studied by comparison of the oxidation behavior of Ni-20Cr thin st rips in air under classical conditions, i.e., without any applied mechanica l load and under tensile creep, at temperatures between 500 and 900 degrees C. The study was performed mainly by comparisons of cross sections of oxid ized samples observed by SEM. The results obtained clearly indicate that ap plying a tensile load induces an increase in the oxidation rate, does not m odify the oxide-film morphology, but promotes the formation of internal oxi dation at low temperatures, 500-600 degrees C, and notably increases the th ickness of the intermediate NiCr2O4 layer at 900 degrees C. This is related to the acceleration of anionic diffusion when a tensile load is applied, d ue to the formation of fast-diffusion by short-circuit paths.