| Abstract Scope |
Inconel 718 (IN718), a nickel-based superalloy used in gas turbines, suffers from strength degradation at high temperatures due to the dissolution of γ' (Ni₃Al, Ti) and γ'' (Ni₃Nb) phases. To overcome this limitation, in this study pre-alloyed IN718 powder was mechanically alloyed with 0.3 wt% Y₂O₃, 0.3 wt% Zr, and 0.5 wt% Hf. Powder forging of IN718 with Y₂O₃, Y₂O₃+Zr, Y₂O₃+Hf, and Y₂O₃+Zr+Hf was performed at 1200 °C to develop oxide dispersion strengthened (ODS) superalloys. The composition containing all three elements showed a 45% and 19% increase in tensile yield strength at room temperature and 650 °C, respectively, over base IN718. SEM and TEM analyses confirmed the formation of thermally stable (above 650℃) nano-complex oxides, such as Y₂Hf₂O₇, Y₂Zr₂O₇, Y₄Zr₃O₁₂, and Y₂Ti₂O₇. These oxides, along with Y₂O₃ dispersoids, contributed to enhanced high-temperature strength through the dispersion strengthening mechanism by effectively impeding dislocation motion, thus preserving structural integrity at elevated service temperatures. |