Gaseous isostatic forging: Design and application to powder metallurgy Ti-6Al-4V

Abstract

For near-net-shape manufacturing technologies such as casting, additive manufacturing, powder processing, and powder injection molding, residual pores and voids are inherent. Gaseous isostatic forging (GIF) provides a rapid and cost effective way to heal these defects. In GIF, isostatic pressure is rapidly applied to heated components by means of a pre-pressurized gas. This rapid pressurization causes internal defects to close through plastic deformation, thus densifying the component. By utilizing plastic deformation, lower temperatures may be used, thus maintaining microstructure integrity. Previous work has shown GIF processing to be an effective method for closing residual porosity and increasing mechanical properties of Ti-6 A l-4V produced by the powder metallurgy process Hydrogen Sintering Phase Transformation (HSPT). However, little information regarding the processing parameters of GIF is known. Therefore, the aim of this publication is to broaden the understanding of GIF processing by investigating various methods for predicting the resulting rapid pressurization based on simple system parameters and observe the effects of processing temperature, starting porosity, and hydrogen concentration on densification and microstructure of HSPT Ti-6 A l-4V.