The process of molding WC-Co feedstock around a high-speed steel (HSS) insert was investigated both experimentally and by mold filling simulation. The effects of the insert on molding defects were explored. The simulations found that heat transfers from the feedstock to the insert, and the insert temperature reaches a maximum of 71.3 degrees C at 200 bar and 82.8 degrees C at 300 bar. WC-Co feedstock cools and solidifies very quickly when it comes into contact with the mold and insert surfaces. Sink marks, pores in the injected part, and a gap at the interface of the HSS insert/injected part were observed depending on the injection parameters in the experimental study. Increasing the mold and insert temperatures reduced sink marks. The injection velocity and pressure affect the gap formed between the insert and the injected part.