In this study, optimum rheological properties for powder injection molding (PIM) of IN718 powder, widely used in aerospace industry, were determined. The feedstocks were prepared 61, 63 and 65% (volume) powder loading rates with three different binding cures using Polypropylene as backbone binder. The mean particle size of used IN718 powder was 13.40 microns. Components used in the binding (Polyethylene Glycol, Paraffin Wax, Carnauba Wax, Stearic Acid and Polypropylene) were mixed for 30 minutes as dry in three dimensional mixer to prepare binder cures. Rheological properties of feedstock were characterized by using a capillary rheometer. In this experimental studies, shear stress (tau), shear rates (gamma) over dot, viscosity (eta), flow behavior index (n) and the flow activation energies (Ea) of feedstocks were determined depending on the temperature and pressure. Temperatures and pressure values of capillary rheometer changed 130-200 degrees C and 0.165-2.069 MPa, respectively. Shear stress (tau) of PIM feedstocks determined between 10.8-135.3 kPa. Apparent shear rates (gamma) over dot of PIM feedstocks were found to be 6.890-814.718 s(-1). Apparent viscosities of feedstocks were calculated within the range 55.349-1571.707 Pa.s depending on the temperature, binder formula, shear stress and shear rate. The flow behavior index (n) parameters for PIM feedstocks were determined to be less than 1. Effects of temperature onto apparent viscosities of feedstocks were also studied and flow activation energies under various shear stresses were determined within the range of 11.750-51.958 kJ/mol.