Hot Isostatic Processing

1
Hot Isostatic Processing

• Improvement of Material Properties
• Lindell Pearson
• AE 510

2
Definition

• Hot Isostatic Processing (HIP)
• Application of high temperature and high pressure
  to remove internal porosity, consolidate powder
  for alloys, and diffuse bond.
  
• Materials that can be HIPped
• Titanium, beryllium, steel, aluminum, superalloys

3
Overview

• Equipment used
• Applications
• Powder consolidation
• Healing of casting defects
• Diffusion bonding
• Aerospace application

4
Hot Isostatic Equipment

• Pressure vessel contains entire process
• Furnace enclosed in vessel
• Pressure vessel insulated from furnace
• Allows combination of high temperature and high
  pressure

5
Equipment (Cont.)

• Pressures reach 200 Mpa
• Temperatures reach 2000 degrees Celsius
• Size of pressure vessel ranges from smaller than
  4X12 up to 46X80
  

6
Applications of Hot Isostatic Processing (HIP)

• Powder consolidation
• Healing of casting defects
• Diffusion bonding

7
Powder Consolidation

• Alloys are sometimes created using Powder
  Metallurgy
  
• Alloys have trouble becoming chemically
  homogeneous
  
• When they are allowed to form on their own they
  form large grains that do not mix as shown at
  right

8
Powder Consolidation (Cont)

• Using HIP it is possible to construct an alloy
  that has good chemical homogeneity and refined
  microstructures
  
• Small grain size, compared to previous slide, can
  be seen at right
  
• Leads to improved mechanical properties

9
Healing of Casting Defects

• Casting defects such as internal pores causes
  weakness in materials
  
• Dark spaces at right are internal pores
• Voids act as stress risers
• Leads to inaccuracy when predicting yield and
  ultimate strengths, scatter

10
Healing of Casting Defects (Cont)

• With HIPping it is possible to change the
  material to a plastic state, collapse the voids,
  and bond the voided surfaces together (right)
  
• The result is a stronger material that has less
  scatter with ultimate and yield strengths.
  
• Accomplished though creep mechanisms and/or
  compressive plastic deformation

11
Diffusion Bonding

• Components can be joined through Hot Isostatic
  Processing using Diffusion Bonding
  
• Two materials undergo no more than a few percent
  macroscopic deformation
  
• Important because welding and fastening produce
  larger deformation which leads to stress points
  and weakening of material

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Diffusion Bonding (Cont)

• Surfaces of materials to be joined bonds
  collapse and join with each other.
  
• The material is then bonded with a 100 perfect
  bond
  
• Barely detectible interface of diffusion bonded
  material seen at right

13
Major Aerospace Application

• Turbine blades
• Need for a blade that has cooling channels to
  encounter high temperatures
  
• Using HIP it is possible to form a component from
  multiple components that are diffusion bonded
  
• Can maintain low weight while being able to
  withstand high temperatures and stresses
  

14
Conclusion

• Hot Isostatic Equipment
• HIP applications
• Heal defects
• Diffusion bonding
• Powder consolidation
• Aerospace Application

15
References

• Hanes, H.D., D.A. Seifert, C.R. Watts. Hot
  Isostatic Processing.
  Columbus, Ohio Battelle Press, 1979.
  
• http//www.imp.mtu.edu/metallic/quick-hip.html
• http//www.irc.bham.ac.uk/theme1/isostatic/facilit
  ies.htm
  
• http//www.kittyhawkinc.com/what_is_hot_isostatic_
  processing.htm
  
• http//www.turboneticsinc.com/HIPcompressorwheels.
  html