3D printed die-casting molds with conformal cooling channels are spreading out to perform rapid uniform cooling. There is high volume demand of large 3D-printed molds, but conventional alloy powder grades for 3D printing, H13 steel and 18%Ni maraging steel, has issues regarding printability and mold life. Especially, H13 steel powder is subject to frequent cracking due to residual stress during 3D-printing. The estimated cause of cracking is the accumulated strain generated at hardening with each printing layer because of its high carbon content and the martensitic transformation start temperature being higher than the preheating temperature. Otherwise, 18%Ni maraging steel powder is used for large molds because of its printability. However, its poor thermal conductivity compared to H13 steel has a high risk of cracking from cooling channels because it needs to be installed near the cavity surface. In addition, the contained cobalt can be harmful to human bodies.

The novel Co-free and high thermal conductivity powder is designed for large-sized molds modified from the chemical composition of H13 steel. The developed powder is designed to have a lower carbon content than H13 steel, resulting in reduced hardness after martensitic transformation. Furthermore, the transformation start temperature was lowered to near the preheating temperature of conventional 3D-printers by Ni adding, which suppress cracking during printing. The mechanical properties and thermal conductivity are comparable with H13 steel.