In situ synthesis and characterization of ceramic reinforced Inconel 718 coatings using B4C-Inconel 718 powders by laser-directed energy deposition

Inconel 718 has been widely used in aerospace, nuclear, and marine industries due to excellent high-temperature mechanical properties and corrosion resistance. In recent years, laser-directed energy deposition (DED) becomes a competitive method in the fabrication of Inconel 718 coatings. Compared with other surface coating processes, laser DED has the advantage of extremely fine-grained structures, strong metallurgical bonding, and high density. However, the hardness and wear resistance of Inconel 718 coatings still need to be improved. To further improve these properties, ceramic reinforced Inconel 718 coatings have been investigated. Compared with ex situ ceramic reinforcements, the in situ synthesized reinforcements have the advantage of refined ceramic particle size, uniform distribution, and low thermal stress. B4C was a preferable additive material to fabricate in situ synthesized multi-component ceramic reinforced Inconel 718 coatings. The addition of B4C could form a large number of borides and carbides as ceramic reinforcements. In addition, the in situ reactions between Inconel 718 and B4C could release heat during the fabrication, thereby promoting the melting of material powders. However, there are currently no investigations on the in situ synthesis mechanisms, microstructure, and mechanical properties of laser DED fabricated B4C-Inconel 718 coatings. In this study, the effects of B4C on the properties of Inconel 718 coatings were investigated. Results show that Ni3B, NbB, and Cr3C2 phases were formed. With the addition of B4C, the size of Laves phase was refined and the porosity was decreased. The hardness and wear resistance of B4C reinforced coatings were improved by about 34% and 28%, respectively.