Ni-based ODS alloy prepared by direct energy deposition process: powder fabrication, microstructure, mechanical property, and oxidation resistance

Additive manufacturing (AM) has generated considerable interest in Ni-based oxide dispersion strengthened (ODS) alloys to achieve enhanced performance of gas turbine engines at elevated temperature. However, fabrication of powder feedstock to achieve uniform distribution of strengthening nanoparticles throughout the matrix is still an open question. This research deals with the fabrication and evaluation of Ni-based ODS alloy powder feedstock for direct energy deposition (DED) process using ball milling (BM) and mechano-chemical bonding (MCB) processes. The formation and stability of nanoparticles, microstructures of as-printed and oxidized alloys were characterized through scanning electron microscope (SEM), X-ray diffraction (XRD), and high-resolution transmission electron microscope (HRTEM), mechanical properties and oxidation resistance of DED-fabricated alloys were also evaluated. The results demonstrate that the DED-fabricated alloys with uniform dispersion of nanoparticles can be achieved by ultrafine oxides embedded powder feedstock. The precipitates play an important role in mechanical strength of as-printed alloys, where an increase in microhardness is observed as the density of precipitates rises with increasing the linear energy. The yttrium-rich nanoparticles exhibit exceptional stability after 2040 thermal cycles. Ultrafine YAlO3, and Y3Al5O12 were observed in alloys printed with both MCB + BM− (R1) and MCB-processed (R2) powders. The formation of Al2O3 provides sufficient oxidation resistance for ODS754 at temperatures up to 1100 °C. Al2O3 remains stable for up to 2040 cycles and ensures exceptional stability of the alloys' microstructure and strength, thanks to the oxide dispersion strengthening (ODS) effects. This study highlights the crucial role of ultrafine oxide particles in the powder feedstock for the successful fabrication of ultrafine oxide dispersed alloys and brings valuable insights into the fabrication ODS powder feedstock for AM processes.