Microstructure and Mechanical Properties of Additive Manufactured Inconel 718 Alloy by Oxide Dispersion Strengthening of Sc Addition

Additively manufactured superalloys have attracted increasing attention due to their inherent hierarchical microstructure, however are plagued by anisotropic properties originated from columnar grains. In this work, scandium was introduced as an oxide dispersion strengthener (ODS) into the Inconel 718 (IN718) alloy fabricated by laser-powder bed fusion (LPBF) to inhibit the formation of columnar grains. The effects of scandium on the microstructure and mechanical properties of the IN718 were investigated. It was revealed that in-situ formed Sc 2 O 3 nanoparticles as well as cellular sub-grains macrostructure with high-density of dislocations were formed in as-built IN718-Sc alloy. With the addition of scandium, typical columnar grains generated by LPBF process transformed to equiaxed grains, accompanied with the strong (100) texture in pure IN718 alloy changing to irregular orientations in IN718-Sc alloy. The average grain size and the aspect ratio also decreased with Sc addition. The as-built IN718-Sc alloy achieved the yield strength of 1030 MPa at room temperature and 837 MPa at 650 ºC. High strength of IN718-Sc alloy at elevated temperatures was attributed to Zener pinning of grain boundaries by dispersed Sc 2 O 3 nanoparticles.. The strategy with dispersed oxide particles to regulate microstructure and improve properties could be utilized as a useful suggestion to conduct for other alloys fabricated by liquid state additive manufacturing