The Co-33Cr-5Mo alloy powders containing nitrogen were prepared by gas atomization and water atomization process, and selective laser melting process was performed using both the powders. Nitrogen contents in both the Co-Cr-Mo powders, which control the phase constitution of Co-Cr-Mo alloys, were almost the same. On the other hand, the oxygen content of the water-atomized powders was higher than that of the gas-atomized powders. SEM observation revealed that the oxide layer containing Cr and Si was formed on the surface, although the clean surface was observed for the gas-atomized powder. It should be noted that the porosity of the SLM build using the gas-atomized powder was higher than that using the water-atomized powder, especially in the case of lower energy density. The porosity difference caused the mechanical properties difference at the lower energy density.
