[en] Development of Y₂O₃-Ti complex Oxide Dispersion Strengthened (ODS) alloys are gaining importance for reactor core application as they show superior mechanical properties at elevated temperatures (∼ 700°C). Addition of Ti is essential, as it refines the Y₂O₃ sizes, by precipitation of Y-Ti-O complex oxides of 3-5 nm size. The structural evolution of these oxides with time under identical mechanical milling conditions is the main objective of this study. In this experiment nano crystalline powders of Y₂O₃ and ZrO₂ are subjected to high energy bail milling for various durations maintaining using optimized milling parameters, milling speed of 1000 rpm and ball to powder ratio of 10:1. Comparative micro structural investigations using Electron Microscopy (SEM, TEM) and X-Ray Diffraction techniques will be presented in the conference

[en] A novel ZrO₂ dispersion strengthened 9 Cr Steel is synthesized via ball milling followed with consolidation by Spark Plasma Sintering (SPS). The consolidated specimen is found to have ∼ 91.2% of theoretical density. Further, the Normalizing and tempering (N and T) treatment is carried out on the consolidated specimen for the release of excess of strain in the matrix and to get the ideal microstructure for obtaining the optimum strength and ductility. The Electron Microscopy technique is adopted for studying the microstructure and to understand the precipitation behavior. Energy Dispersive X ray spectroscopy (EDS) is utilized for understanding the chemistry and homogeneity of the sample. The EDS analysis showed the presence of Cr and W rich precipitates in the matrix. Variation of hardness with heat treatments is monitored and correlated with the Yield strength. Comparison is also drawn from the other candidate material for nuclear core applications, such as conventional Y₂O₃-Ti complex oxide strengthened steel (Y - ODS) and Reduced Activation Ferritic Martensitic (RAFM) steels. (author)

[en] Highlights: • Laser-remelted YSZ TBCs showed chemical inertness in molten sodium. • LSR produced a dense, columnar and smooth surface architecture in YSZ TBCs. • Vertical segmented cracks allowed molten sodium infiltration and disintegration at non-remelted interfaces. • The corrosion mechanism of LSR YSZ in molten sodium is primarily of physical decohesion at weak boundaries. Liquid-metal corrosion in molten sodium is a significant issue to Thermal Barrier Coatings (TBCs) proposed for in-core fast breeder reactor applications. In this study, the viability of attenuating molten sodium corrosion of plasma-sprayed yttria-stabilized zirconia TBCs is investigated by microstructure re-engineering using Laser Surface Remelting (LSR). LSR produced a smooth and dense surface with columnar microstructure and segmented vertical cracks. At the onset of molten sodium corrosion, the remelted layer retained structural integrity but exhibited localized corrosive attack along the surface-network cracks. However, on further exposure, the vertical cracks lead to molten sodium infiltration down the non-remelted layers, causing corrosive damage and spallation of coating.