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| The Isostatic
Principle |
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Isostatic Pressing is the application of pressure to a material via a
pressurized fluid medium,
completely uniform in all directions
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Isostatic Pressing |
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Hot
Isostatic Pressing was developed at Batelle Laboratories in Columbus,
Ohio (USA) during the late fifties and early sixties.
During
a HIP
cycle, materials are subjected to a combination of elevated temperature
and isostatic pressure. The result is elimination of internal porosity
(voids). HIP is effective with almost all materials - metals, ceramics
and plastics.
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- HIP
temperature depends on the material being processed - typically 500
°C for Aluminum Alloys, 1170 - 1220 °C for superalloys,
1600 - 2000+°C for superalloys
- HIP pressure is normally in the range
of 500 - 2000 Bar
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Current
applications of HIP include:
- consolidation
of encapsulated powders into billets or near-net-shape products, or as
claddings on solid substrates. HIP is particularly suited to material
compositions that are difficult to sinter to full density - for
example; metal-matrix composites and low-glass ceramics
- removal of residual porosity from
castings and welded joints, resulting in;
- enhanced mechanical properties - especially
fatigue strength
- improved machined surface finish
- enhanced pressure tightness
- improved x-radiographic quality
- rejuvenation
of
service-deteriorated components - for example; sprayed coatings with
improved bond strength and density
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HIP
is widely used on:
- Ni-based superalloy gas-turbine components
- Titanium,
Steel and
Aluminum alloy castings
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Isostatic Pressing |
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CIP
is
widely used to compact powders, the particular benefits being:
- consistant density throughout the
compact, resulting in uniform and predictable shrinkage during
subsequent sintering
- shape flexibility (three dimensional)
of the compact as a result of the isostatic pressure application.
Major
application areas for CIP include:
- hard metals - for example; tungsten carbide
- graphite and ceramic based refractories
- structural ceramics - for example;
alumina, silicon carbide
- metal powders - for example;
stainless steels
- plastics - for example; PTFE
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| © Isostatic Forging International
2005 |
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