An elastic analysis of growth stresses during oxidation

A quantitative analysis of oxide growth stresses is carried out for the model advanced by Rhines and Wolf in which new oxide forms along preexisting oxide grain boundaries. The mean oxide stress developed within the oxide is calculated using standard techniques from continuum dislocation theory. This analysis shows that the mean growth stress is compressive and is directed parallel to the oxide/ matrix interface. The growth stress is found to be independent of the oxide scale thickness, provided that the scale is thicker than the oxide grain size. However, in thin scales, the growth stress is very sensitive to oxide scale thickness. The compressive growth stress increases in direct proportion to the width of the new grain boundary oxide layer formed. The oxide scale is expected to either fail by buckling, or the growth mode will change to one in which additional compressive stresses are not generated.