Strengthening Additively Manufactured Inconel 718 Superalloy Through In-Situ Formation of Carbide and Silicide Nanoprecipitates

Abstract

We report additive manufacturing of a nickel superalloy metallic matrix composite (Ni-MMC) using Laser Powder Bed Fusion (LPBF). Nanoceramic-containing composite powders were prepared by high-speed blender declustering and ball milling of as-received SiC nanowires (2 vol%) and base Inconel 718 alloy powders, which produced a homogeneous decoration of SiC on the surfaces of Inconel particles. Analysis of the as-printed specimens revealed the dissolution of SiC nanowires during laser melting, leading to the in-situ formation of Nb- and Ti-based silicide and carbide nanoparticles. These in-situ formed nanoparticles resulted in the formation of a more desirable solidification microstructure of the additively manufactured Inconel 718 with less printing defects (cracks and pores) and refined grain sizes. Mechanical characterization of the as-printed Ni-MMC composites revealed notable increases in hardness, yield strength (by 16%), and ultimate tensile strength (σUTS, by 12%) compared to the reference samples without SiC addition. After heat treatment, these same composite samples displayed a 10% higher σUTS compared to identically treated unreinforced material while maintaining ~14% total tensile elongation. We believe this in-situ precipitate formation presents a simple and effective method for strengthening additively manufactured high-temperature materials that may prove important in addressing the increasingly harsh environments in energy and propulsion applications.

Keywords: Silicon carbide, Inconel 718, Laser powder bed fusion, Ductility