A research team from Harbin Institute of Technology (HIT) systematically investigated droplet behavior and melt pool dynamics during single-track deposition of Inconel 718 alloy and TiC/Inconel 718 composites via selective arc melting (SAM) additive manufacturing, using high-speed camera in-situ observation. Results show that the melt pool of Inconel 718 alloy relies mainly on periodic droplet impacts from surrounding area, leading to severe melt pool fluctuations, numerous 1–2 mm hemispherical protrusions on sidewalls, and harmful chain-like Laves phases in the microstructure. In contrast, the addition of TiC alters the physical properties of the molten metal; the melt pool material primarily originates from in-situ melting in the arc central region, significantly improving melt pool stability, reducing sidewall surface roughness, and generating finely dispersed carbide particles in situ while almost completely eliminating chain-like Laves phases. The study elucidates the formation mechanisms of sidewall protrusions and surface height differences, providing a theoretical basis for process optimization and defect control in superalloy-based composite wire-arc additive manufacturing.