Forging super alloys and other materials that have a low forgeability, can create difficulties during a metal forging process. Also, mechanical properties of some metals may vary greatly over small temperature ranges. To help eliminate some of the problems associated with manufacturing with these types of materials, particularly with regard to more complex parts, isothermal forging may be employed. This process is also called hot die forging.
Isothermal forging is a hot working process that attempts to maintain the work piece at its maximum elevated temperature throughout the entire operation. This is achieved by heating the die to the temperature of, or slightly below the temperature of the starting work piece. As forces exerted by the die form the work, cooling of the work piece between the mold work interface is eliminated, and thus flow characteristics of the metal are greatly improved. Isothermal forging may or may not be performed in a vacuum. Equipment costs for this manufacturing process are high, and the added expense of this type of operation should be justified on a case by case basis.