High temperature oxidation of Ni70Cr30 alloy: Determination of oxidation kinetics and stress evolution in chromia layers by Raman spectroscopy

In this work, the oxidation of Ni70Cr30 alloy has been produced at a temperature of 900 °C in air. The parabolic behaviour of oxidation was established ex situ and the corresponding kinetic constant was deduced. Microscopic observations have shown that chromia grain size does not exceed 1 μm. Raman spectroscopy was used to determine stresses in chromia (Cr2O3) layers. Stresses are found to be compressive and increase with the chromia thickness before reaching a “plateau” at −2.9 GPa. The stress relaxation phenomenon discussed here takes into account theoretical modelling that can be found in literature.