Inconel 718 coating has been applied in various applications such as aviation impellers and gas turbines due to its excellent tensile properties, high impact toughness, corrosion resistance, and creep resistance. However, its low hardness and poor wear resistance restrict its broader applications. In this study, laser directed energy deposition (DED) is utilized to in-situ synthesize TiB2, TiC, and (Ti, Nb)C ceramic phases, which improves the mechanical properties of the Inconel 718 coating. The effect of five coatings with different Ti and B4C contents on phase, microstructure, microhardness, scratch, and wear resistance was studied. Gibbs free energy (G), SEM, EDS, and EBSD were used to analyze experimental phenomena. The results showed that TiB2, TiC, and (Ti, Nb)C ceramic phases were in-situ synthesized. The (Ti, Nb)C phase with a loop shape was around TiC phase and TiB2 phase, which were found on the Laves phase and at grain boundaries. The formation and positional relationship of the Nb atom and Ti atom in MC (refer to TiC and (Ti, Nb)C) crystal structure have been investigated. The distribution of Ti atom and Nb atom within the MC crystal structure, as well as their effect on G, have also been analyzed. The mechanical properties of Inconel 718 coating have been significantly improved as a result of fine-grain strengthening, solid solution strengthening, and second-phase strengthening. The addition of B4C + Ti content can considerably enhance the microhardness of Inconel 718 coatings by 62.96 %, and the fitting function of powder content and microhardness has been obtained. The deformation resistance is increased, and the toughness is reduced. The deformation of the scratch has been translated from plastic deformation to shear deformation. In addition, the wear mechanism of the coating changed from adhesive wear to abrasive wear, and the minimum wear rate is 1.70 × 10−4 mm3/Nm. This study.
proposes a novel approach for improving the mechanical properties of Inconel 718 coating, as well as provides guidelines for coating preparation.