Development and characterization of oxide dispersion strengthened Ni-Mo alloys for enhanced performance in harsh environments

The development of advanced structural materials with superior properties for harsh service environment is critical for the advancement and commercialization of next-generation energy systems, such as nuclear reactors, that support decarbonization efforts. Advanced powder metallurgy techniques combined with mechanical alloying provide a unique approach for rapid material synthesis and property optimization. In this study, Ni-Mo alloy and its variants, incorporating yttrium (0.05 wt%) and yttrium oxide (Y₂O₃, 1 wt%) were synthesized and evaluated for their microstructural characteristics, mechanical properties, and densification behavior. The results revealed that both Ni-Mo and Ni-Mo-Y contained large MoO₂ particles and fine CrO₂. Additionally, Ni-Mo-Y exhibited the presence of Y₂O₃ due to the yttrium oxidation. The Ni-Mo-Y-Y₂O₃ contains dispersed Y₂O₃ nanoparticles at the grain boundaries, resulting in superior tensile strength compared to the non-Oxide Dispersion Strengthening (ODS) variants. The Ni-Mo without any Y₂O₃ dispersion also exhibited high tensile strength, which was attributed to the presence of MoO₂ particles at the grain boundaries. Hydrogen-treatment of the ball-milled powders effectively eliminated MoO₂ formation on powder surface. Samples fabricated from the treated powders exhibited reduced tensile strength and improved ductility. The strengthening mechanisms in these alloys were studied, showing good agreement between experimental values and theoretical calculation. The addition of Y₂O₃, however, slowed densification kinetics and required a higher sintering temperature to achieve full densification.