Influence of cooling rate and initial surface roughness on the residual stresses in chromia scales thermally grown on pure chromium

Raman spectroscopy was used to determine the residual stresses in chromia scales grown on pure chromium by thermal oxidation in dry oxygen. After oxidation, these stresses are compressive and are shown to depend on both the cooling rate and the initial surface roughness of the substrate. These parameters also have an influence on oxide spallation, but it is observed that the relationship between stress level and spallation is not a direct one. A model is proposed to explain the tendency for chromia scales to spall, which considers the importance of initial surface roughness and oxide stresses.