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Isostatic Pressing is the application of pressure to a material via a pressurized fluid medium, completely uniform in all directions



Hot Isostatic Pressing

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.


 

  • 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

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

HIP is widely used on:

  • Ni-based superalloy gas-turbine components

  • Co-Cr medical implants

 

  • Titanium, Steel and Aluminum alloy castings

Cold Isostatic Pressing

CIP, often using a liquid / water-based pressurizing medium, usually takes place below 60 °C. Pressures are usually in the range of 1000 - 5000 bar.


 

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