Growth stresses in α -Cr2 O3 thermal oxide films determined by in situ high temperature Raman spectroscopy

Growth stresses have been investigated in relation with the microstructure in the case of α -Cr2 O3 growing oxide films on NiCr30 alloy. The equibiaxial growth stresses have been measured thanks to a technique coupling Raman spectroscopy and in situ high temperature oxidation of the NiCr30 alloy in the temperature range (700-900 °C). It is established that the compressive growth stress in such oxide films can reach more than 2 GPa, before additional thermal stress arises on cooling. Moreover, the growth stress kinetics-subsequent establishment and relaxation-are highly microstructure sensitive: in particular, as the oxidation temperature rises, the chromia mean grain size also increases, and it consequently retards the occurrence of the creep relaxation phenomena which needs an additional stress level to start. © 2007 American Institute of Physics