Microstructural Characterization and Role of Glassy Layer Developed on Inconel 690 During a Nuclear High-Level Waste Vitrification Process

The interaction of Inconel 690 metallic components with borosilicate melt leads to development of a partially amorphous and a partially crystalline layer within borosilicate melt adjacent to the interface. Such a heterogeneous layer is referred to here as a glassy layer. In the present investigation, the glassy layer is constituted of several phases, e.g. a Cr₂O₃ layer, a Ni₂CrO₄ needle, and NiCr₂O₄ cubic phases. Incorporation of such a glassy layer within the melt pool can lead to significant microstructural changes in the melt. Formation of barium chromate and nickel silicate has been observed in a sodium barium borosilicate melt with excess amount of Cr₂O₃ and NiO, respectively.