Powder Metallurgy Hot Isostatic Pressing (HIP)
Hot Isostatic Pressing of encapsulated powder metals produces net or near net shape parts with special particle properties. The process takes place well below the melting point of the material, typically resulting in a very fine grained structure. HIPped P/M parts are isotropic and represent a significant potential savings in material and lead time compared with wrought components.
For optimum consolidation, powders are encapsulated in a container, generally of mild or stainless steel, which must be free from any leakage at the elevated temperature and pressure of the HIP process. The container must be cleaned before encapsulation to avoid unwanted reactions and impurities. Evacuation, sealing and pressing are the final steps, resulting in fully dense PM components.
HIP enhances the versatility and design flexibility inherent in powder metallurgy. The wear resistance of PM tool steels can be improved by mixing the steel powders with a higher volume content of particles like carbides, nitrides, oxides, borides or silicides. Low density, high stiffness, light alloy based materials with ceramic particles can be produced. The process allows freedom in chemical composition, particle size, distribution, form and even permits graded structures. In addition, solid/solid, powder/solid or powder/powder composite products can easily be produced with perfect bonds between the layers.
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