Enhanced high temperature mechanical and oxidation behavior of direct energy deposited TiC/Inconel 718 gradient coatings

• This paper presents a method to control microstructure evolution of TiC/Inconel 718 gradient coating via gradient TiC addition. • The gradient method for adding TiC has achieved a gradient increase of reinforced particles. • Enhanced high temperature mechanical and oxidation behavior of TiC/Inconel 718 gradient coating were obtained by the gradient method for adding TiC. While Inconel 718 is commonly employed in high-temperature settings, its performance at elevated temperatures is notably diminished in comparison to its performance under ambient conditions. In this study, Inconel 718 (IN718), Inconel 718 with 5 layer of Inconel 718–5 wt% TiC gradient coatings (CG-5), and Inconel 718 with 5 layer of Inconel 718–10 wt% TiC gradient coatings (CG-10) were fabricated using direct energy deposition (DED) to investigate the influence of TiC content on the mechanical and oxidation properties at elevated temperatures through the regulation of microstructural changes. Following the incorporation of TiC, the microstructures underwent a transformation into refined equiaxed crystals, carbides, and columnar crystals, replacing the coarsened columnar crystals and Laves phase present in IN718. Compared to IN718, the high-temperature tensile strength of CG-5 and CG-10 has increased by 80% and 180% at 900 ℃. Meanwhile, the mass gain due to oxidation per unit area of CG-5 and CG-10 has decreased by 23% and 11%, respectively. The results indicate that CG-10 exhibits a combination of highest high-temperature tensile strength and the enhanced resistance to high-temperature oxidation when compared to IN718 and CG-5.