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.