Consolidation methods isostatic pressing

The die-and-punch method of compact imparts an anisotropic pressure to the compact. It is possible to apply pressure equally in all directions using a process called isostatic pressing, in which the powder is compacted with a fluid, such as hydraulic fluid, water, or an inert gas. Isostatic pressing is carried out using formed, flexible molds, called cans, that contain the powder and allow the pressure from the fluid to be transferred to the powder. The flexible molds are then stripped off the compact after densification. Isostatic pressing eliminates the die-wall friction inherent in die compaction and allows for consolidation of large components. However, isostatic pressing... 

Today, the best method of overcoming the problem of uneven densities in a green body is isostatic pressing. In this compaction process, the pressure is applied by a fluid that is pressurized and acts uniformly from all sides on dry particulate solids that are enclosed in a flexible container ( mold ) immersed in the fluid [B.13a]. This results in the most uniform consolidation possible. Of course, there is still a density gradient across the part, the center is always less compacted than the surface, but the gradient is uniform and, typically, does not cause distortion during sintering. 

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