For process optimization purposes during die filling, it is crucial to understand the impact of process parameters as well as powder morphological and physical parameters. In this context, the Discrete Element Method (DEM) can serve as a tool for predicting powder behavior in production processes of PM parts. Therefore, in the present work DEM models for simulating the filling process are calibrated via a Rheometer-based characterization method suitable for the filling regime of interest, i.e. gravitation induced powder flow. Tests are performed both experimentally and numerically for different powder types in order to inversely extract the powder material-specific parameters of the DEM-based process model. In particular, standard hardmetal powder type WC-Co with average granule size of up to 400 µm as well as a standard Mo powder grade with average grain size of 4.6 µm are analyzed and characterized accordingly. The received material-specific parameters are then ready to use for further validation in the form of input for DEM models of industrial filling processes.