An example mold assembly for fabricating an infiltrated downhole tool includes a mold defining a bottom of the mold assembly and a funnel operatively coupled to the mold. An infiltration chamber is defined at least partially by the mold and the funnel to receive and contain matrix reinforcement materials and a binder material used to form the infiltrated downhole tool. A thermal mass is positioned within the infiltration chamber above the infiltrated downhole tool for imparting heat to the infiltrated downhole tool following an infiltration process.