Ametek, Specialty Metal Products Division

Edwin S Hodge

Robert F Tavenner

A pneumatic isostatic forging process for densification of near net shape workpieces is disclosed. In the process, a workpiece is heated prior to the forging process, such as from a previous processing step. The workpiece is loaded into a pressure vessel. The pressure in the vessel is ramped to an operating pressure and held for approximately 10-120 seconds. The vessel is pressurized using rapid pressurization to achieve a high strain rate to assist in the final closure of voids within the workpiece, with the increase in the strain rate lowering the flow stress requirements for the workpiece, thereby making the workpiece more susceptible to plastic deformation. The rapid pressurization serves to densify the gas within the vessel, thereby increasing the viscosity of the gas in order to substantially reduce or altogether prevent absorption of the gas into the workpiece in order to sustain a differential between the internal pressure and the surface pressure of the workpiece, thereby allowing plastic deformation to take place through a collapsing of the material, or removal of the voids. After pressurization of the vessel for a prescribed period of time, it is depressurized and the workpiece is unloaded.

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Ocala, FL, United States of America

Edwin S Hodge