A STUDY OF THE INTERPHASE STRUCTURE AT THE OXIDE METAL INTERFACE IN THE CORROSION OF ZIRCONIUM-BASED ALLOYS

The nature of the oxide layer that formed during corrosion of zirconiu m-based alloys in a pressurized, lithiated water environment at 300 de grees C was determined through scanning electron microscopy (SEM) stud y of the oxide-metal interface region as well as X-ray diffraction (XR D) and electron diffraction (ED) analyses. Alloys examined included co ld-worked Zr-2.5wt%Nb, heat-treated Zr-2.5wt%Nb, Excel alloy (Zr-Sn-Mo -Nb), pure zirconium and cold-worked Zircaloy-4 (Zr-Sn alloy). The met allographic observations and corrosion kinetics studies show that vari ations in the oxidation rate among the zirconium-based alloys result f rom the differences in structure of the interphase layer at the oxide- metal interface