Multiphase and microstructural engineering of DED-LB-fabricated Ni solid solution-nickel silicides with alloying addition and heat-treatment for improved mechanical, oxidation/corrosion performance

The eutectic Ni solid solution (Niss)-Ni 3 Si alloy is attractive for structural and coating applications in high-temperature and harsh environments due to its high melting temperature, good strength, and excellent oxidation and corrosion resistance. However, their low fracture resistance limits the fabrication of structural components and limits practical application. This study aimed to improve the processability, microstructural stability, and performance of Niss-Ni 3 Si-based alloys through targeted alloying. In this work, near-eutectic ∼ Ni-12Si was modified with individual additions of V (5 wt%), Cr (3 wt%), or C (0.3 wt%) and fabricated by laser-based directed energy deposition (DED-LB) to obtain Niss-Ni 3 Si-based alloys with improved properties. The V- and Cr-containing alloys developed a Niss-Ni 3 Si microstructure containing columnar metastable γ-Ni 31 Si 12 together with element-rich precipitates in the as-printed state, whereas carbon promoted a more equiaxed morphology. These microstructural modifications improved mechanical, oxidation, and corrosion performance. However, rapid solidification promoted the formation of metastable γ-Ni 31 Si 12 , leading to microstructural and property instability. To address this, post-deposition heat treatment was employed to transform γ-Ni 31 Si 12 into the Ni 3 Si. Overall, the combined control of alloying, eutectic morphology, and metastable phase transformation improved fracture resistance, high-temperature oxidation and corrosion performance, providing an effective alloy and processing strategy for the fabrication of Niss-Ni 3 Si-based parts by DED-LB process.