A research team from the University of South China, in collaboration with the Leibniz Institute for Solid State and Materials Research in Germany and the Harbin Institute of Technology, has developed a high-performance CoCrNi-based composite designed for additive manufacturing through grain boundary segregation. Using laser powder bed fusion (LPBF) and incorporating micron-sized TiC particles, the team successfully produced crack-free, high-strength CoCrNi medium-entropy alloys. Mechanistic studies revealed that TiC addition promotes carbon segregation to grain boundaries, significantly reducing grain boundary energy and effectively suppressing thermal cracking. Additionally, partial dissolution of TiC during PBF-LB formed nanoscale Cr23C6 precipitates and TiC/TiO₂ core-shell structures, refining the grains. The CoCrNi-3 wt% TiC composite exhibited excellent mechanical properties and high-temperature oxidation resistance, with the fine-grained structure promoting the formation of a dense Cr₂O₃ protective film. This research provides a new theoretical framework for designing high-performance alloys for additive manufacturing.