Effect of TiC Content on Mechanical Properties and Microstructure Evolution of TiC/Inconel 718 Functionally Gradient Materials by Direct Energy Deposition

TiC/Inconel 718 functionally gradient materials are prepared by direct energy deposition technology. The effect of TiC content on microstructure and mechanical properties of TiC/Inconel 718 functionally gradient materials is studied. With the increase of TiC content, the microhardness and carbide grain of the specimen are improved, and the density is reduced. The grain of the specimen changes from columnar dendrites to equiaxed crystal, and the equiaxed crystal size is decreased with the increase of TiC content. However, when TiC content is above 10 wt%, the number and size of the Laves phase, coarse TiC primary, and TiC secondary dendrite are increased which causes the generation of cracks. When the TiC content is above 5 wt%, the size of carbide and the number of cracked UMT increase and the impact toughness decreases. Therefore, the optimal maximum TiC content of TiC/Inconel 718 functionally gradient materials is 5 wt% when the laser power is 2200 W.