The oxidation of alloy 690 in simulated pressurized water reactor primary water

The oxide film formed on alloy 690 in simulated pressurized water reactor primary water is decorated with NiFe2O4 particles which remain epitaxial with matrix. The penetrative inner oxides on both surface and crack wall are composed of Cr-rich (Fe,Cr,Ni)3O4 and Cr2O3 which were formed by solid state reactions of substrate with inwards diffusing oxygen and have orientation relationships with the substrate. Cr2O3 forms first along the widely spaced planes of substrate. Compact Cr2O3 layer cannot develop as there is no long-range outward diffusion of Cr in substrate with low defect density at low temperature.