A study of direct forging process for powder superalloys

Powder metallurgy (PM) processing of nickel-based superalloys has been used for a wide range of near net-shape fine grained products. In this paper a novel forming process, i.e. direct forging of unconsolidated powder superalloys is proposed. In this process, encapsulated and vacuumed powder particles are heated up to a forming temperature and forged directly at high speed to the final shape, by using a high forming load. Experiments of direct powder forging have been conducted on an upsetting tool-set. Microstructure, relative density and hardness of the formed specimen have been investigated. A finite element model of the direct powder forging process has been established in DEFORM and validated by the comparisons of experimental with simulation results of load variation with stroke as well as relative density distribution. The stress state and the relative density variation have been obtained from FE simulation. The correlation between the stress and consolidation condition has been rationalised. The developed FE model can provide a guide to design the geometry and thickness of preform for direct powder forging.