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Hot Isostatic Pressing (HIP)

Hot Isostatic Pressing (HIP)

Hot Isostatic Pressing (HIP) is a densification process using heated gas (usually argon) in a furnace under very high pressure and temperatures to densify powders or casted parts. Pressure is applied uniformly around an object which allows for elimination of porosity without changing an objects net shape. This process is used to treat preformed metals or ceramics to improve their physical properties, or to convert powdered metals within a container into fully dense components. A wide range of component types can be manufactured by this process, ranging from small to large components, as well as simple to complex shapes. The HIP process has proven to be a high quality and cost-effective process in the production of many metal, ceramic, or composite parts.

Common Materials Edit

  • super alloys
  • high speed steels
  • stainless steels
  • titanium and aluminum alloys
  • refractory metals
  • carbides
  • engineered polymers
  • advanced ceramics
  • cermets
  • ferrites
  • composite materials

Parameters Edit

The technological parameters that should be controlled are: the temperature, the pressure applied, the timing of the different periods of temperatures and strength application, because the HIP has to be performed by keeping great attention about the features of the dynamic behavior of the processed materials, in which the relation between deformation speed and strength varies as an exponential function. It is worth noting that the permanence of the materials at high temperature can imply the coales-cence of the grains of the hot metal that sometimes requires a successive strengthening treatment (i.e. aging treatment).    


Process Variations Edit

Powder Metallurgy Edit

Description Edit

Uses Powder Metals in a Hot Isostatic Pressing unit in order to develop metals or bimetallic materials that are much stronger and reach near 100% theoretical density.  Due to the process, the created steel has a better microstructure than that of the same material created through other processes. The productions of parts are made near net shape which greatly reduces or eliminates the need for further Machining or welding.

Design Considerations

  • Container Shrinkage
  • Container Production
    • Welding Locations
    • Integrity of the welds
    • Vacuum sealed
  • Container Temperature
  • Pressure
  • Process Time

Typical Tools Edit

  • Compressor
  • Compressible gas(Argon)
  • Heating Element
  • Containment vessel
  • Powder Metal

Geometry capabilities Edit

  • Design Can be simple shapes or complex shapes
    1. Simple shapes- made near net shape
    2. Complex Shapes- Eliminate the need for Machining

Largest Presses up to 66in in diameter and 100in long

Cast Treating Edit

Description Edit

The use of a Hot Isostatic Press to treat pre-made products in order to increase the yield strength, Density, and overall durability of the products.

Design Considerations Edit

  • How many Products to be treated
  • Size of the Products
  • Shrinkage of Parts
  • Temperature
  • Pressure
  • Process time

Typical Tools Edit

  • Compressor
  • Compressible Gas(Argon)
  • Heating Element
  • Containment Vessel
  • Pre-made parts

Geometry capabilities Edit

  • Largest Presses up to 66in in diameter and 100in long
  • The capacity of the products able to be treated is dependent on the size of the Hot Isostatic Press.
Diffusion bonding

Metal Cladding Edit

Description Edit

The hot isostatic press is used to apply a stronger, more durable, and abrasive resistant finish to any product. This is done by applying a metal or bimetallic powder to the outside of an already complete product.

Design Considerations Edit

  • Temperature
  • Pressure
  • Process time

Typical Tools Edit

  • Compressor
  • Compressible gas(Argon)
  • Heating Element
  • Containment Vessel
  • Pre-made parts
  • Solid/Powder Metal or bi metal

Geometry capabilities Edit

  • Largest Presses up to 66in in diameter and 100in long
  • The capacity of the products able to be treated is dependent on the size of the Hot Isostatic Press.

Surface Finishes and Tolerances Edit

Hot Isostatic Pressing technology allows the ability to create Metal and Products with a finish that is more durable than Products created from other processes. This technology also produces a Product that requires little or no finishing operations. The application of temperature and pressure causes the material to densify and reach 100% theoretical density. Products made through hot isostatic pressing have a tight tolerance and due to the material optimization, create high performance finished products.


Container Manufacturing Edit

  • Container sheet cutting and forming
  • Assembling the sheets with other necessary pipes or inserts
  • Leak testing, by evacuating the container and introducing inert gas under pressure

Vibration table Edit

When powder is introduced into the container, a vibration table is used. This allows the powder to fill narrow spaces

Out-gassing Edit

Removal of absorbed gases and water vapor. The fill tube is welded to seal the container. The absence of leaks is absolutely critical in the Hot isostatic pressing process. If a leak were to occur during the process, Argon gas would fill the pores of the material which would greatly reduce the material properties of the final product.

Container Removal Edit

  • Machining
  • Acid Pickling
  • Slipping off

Container Materials Edit

Container Materials and thickness are very important parameters when designing a PM HIP part. Most common container materials are low carbon steels or stainless steels. Normal thickness varies between 2 and 3 mm. The container must satisfy the following considerations:
  • Strong enough to maintain shape prior to and during HIP
  • It must be soft and malleable at HIP temperature
  • Non-reactive with the powders during the process
  • It must be leak proof
  • It must be weldable for secure sealing
  • It must be removable after HIP

Future Developments Edit

The success of Hot Isostatic Pressing over the past few decades proves that HIP is the premier method of producing strong and durable products.

  • Main emphasis on projects with expectations for large

commercial impact.

  • Custom Tailored Materials.
  • Combining HIP with Spray Deposition.
  • The National Nuclear Laboratory is currently developing

HIP for the immobilization of plutonium-containing waste. HIP has the potential to be the center of waste immobilization technology because it has the ability to consolidate waste into durable waste forms.

References Edit


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HIP diagram
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