Cracking is a critical challenge for the application of additive manufacturing (AM) for producing nickel-based superalloys with high γ′ content via laser powder bed fusion (LPBF). This study systematically investigated the effects of alloying elements on the cracking susceptibility and microstructure of René 104ScY fabricated by LPBF. The effects of Sc and Y elements on solidification behavior, microstructure evolution and crack inhibition were discussed. The results show that the nano-Al3(Sc, Y) precipitates in René 104ScY alloy refine both grain and cellular structure sizes, triggering the columnar-to-equiaxed transition, and efficiently inhibiting crack formation. The formation of various dislocation substructures and crossed stacking faults (SFs) with Lomer-Cottrell (L-C) locks are responsible for the synergistic enhancement in strength-ductility of René 104ScY. Crack-free René 104ScY with enhanced strength-ductility were obtained by Sc and Y microalloying. These results provide a novel approach to developing crack-free nickel-based superalloys for AM and offer insights for addressing high cracking susceptibility in other alloys.