Relationship between Residual Stresses and Damaging in Thermally Grown Oxide on Metals: Raman Spectroscopy and Synchrotron Micro-Diffraction Contributions

Ni-30Cr and Fe-47Cr alloys have been oxidized at 900 and 1000°C in air. The influence of the oxidation and cooling conditions on the magnitude of residual stresses present in the oxide scale as well as the existing relaxation modes are studied. A rigorous determination of the residual stresses at both macroscopic scale in the oxide film adherent to the substrate and local scale over the damaged areas allows a comparison with models describing thin film delamination. A multi-scale approach is then proposed : Residual stress levels are determined thanks to conventional x-ray diffraction and Raman spectroscopy while mappings are done over different types of buckling using Raman micro-spectroscopy and synchrotron micro-diffraction. Additional morphological information combined to associated stress levels is injected in the mechanical laws for buckling in order to extract the interfacial toughness.