A method of forming a metal single crystal turbine component with internal passageways includes forming a polycrystalline turbine blade with internal passageways by additive manufacturing and filling the passageways with a core ceramic slurry. The ceramic slurry is then treated to harden the core and the turbine component is encased in a ceramic shell which is treated to form a ceramic mold. The turbine component in the mold is then melted and directionally solidified in the form of a single crystal. The outer shell and inner ceramic core are then removed to form a finished single crystal turbine component with internal passageways.