An ultrasonic fabrication process for carbides reinforced Inconel 718 alloy composites

A novel approach was proposed to prepare carbides reinforced Inconel 718 alloy composites by ultrasonicating graphite mold to introduce carbon element into liquid phase. The graphite mold was designed to resonate with three-dimensional (3D) power ultrasounds, which stimulated cavitation effect and acoustic streaming to promote uniform carbon dispersion and the subsequent incorporation of various carbides with alloy solidification process. It was found that the carbon content infiltrated into liquid alloy increased with ultrasound amplitude and dimension, which attained the maximum of 2.64 wt% C. Ultrasound accelerated the peritectic L+TiC→NbC reaction, forming a blocky (Ti, Nb)C phase instead of shell-core structured (TiC+NbC) phases. A new (Cr, Fe)₇C₃ phase was produced due to the extended carbon solubility into liquid alloy under 3D ultrasounds. Meanwhile, the synergistic orientation relationships between γ(Ni) and carbide phases were enhanced by high-frequency vibration. The ultrasonically solidified composites exhibited excellent wear resistance and hardness as compared with other IN718 alloy-based composites.