Selective laser melting of crack-free René 104 superalloy by Sc microalloying

•A crack-free René 104 superalloy with a refined microstructure was fabricated by SLM with the microalloying of Sc.•Al3Sc nanoparticles promoted the heterogeneous nucleation of Ni to refine the grains.•The cracking elimination was ascribed to the alleviation of enriched Mo, Zr and B and accumulated thermal stress.•The heightened tensile performance was due to the cracking elimination, refinement of grains and Al3Sc nanoparticles.