By Nick Gilbert
Introduction to HIP
How Does HIP Work?
HIP In Manufacturing
Applications and Products of HIP
Benefits of HIP
Hot Isostatic Pressing is a manufacturing technique designed to increase the density of materials by reducing or eliminating their porosity or microporosity thus creating fully dense ‘wrought’ materials. Hot Isostatic Pressing (HIP) is a process employed to enhance or create materials or products with different mechanical properties by improving density, composition and dynamic strength.
The definition of ‘isostatic’ (subjected to equal pressure from every side) gives us a fundamental clue to the basic mechanics of HIP.
During Hot Isostatic Presing, pressure is applied to a material uniformly from all directions through an inert gas (such as Argon) in a pressurized vessel. Throughout the process heat is applied to the containment chamber to increase this pressure over time. It is important to note that the temperature employed is typically below the melting point of the material being pressed.
An inert gas is used to ensure that no chemical reaction occurs with the material during the process. The application of both heat and pressure simultaneously on all surfaces of a material helps to eliminate any small gaps (pores) in the material and hence increases density and uniform composition.
HIPs come in many forms, shapes and sizes and can operate at a range of temperatures and pressures. The following video is a great introduction to HIP:
Introduction to HIP Video
Run Time – 7:31mins
HIP can be used to press a range of materials from Ceramics and Aluminium castings to Nickel based ‘super-alloys’ for all sorts of applications.
Typical materials processed by HIP could be:
- Metal Powder Castings
- Low Carbon Steels
- Stainless Steels
- Nickel-based Super-alloys
- Cobalt-based alloys
- Tungsten Carbide
HIP is widely used during the manufacture of high integrity and precise components for a diverse range of applications and industries from Aerospace and Medicine to Automotive.
- Medical Implants
- Bi-metal materials
- Sintering (Powder metallurgy)
- Ceramic parts
- Metal Matrix Composites
- Super-Alloy Castings
- Titanium Castings
- Gas Turbine Components
- Cutting Tools
- Plastic and food extrusion technology
- Heat Treatment
- Diffusion Bonding
- HIP Brazing
HIP allows us to squeeze the impurities (pores) out of materials in order to improve a number of their material characteristics. For example, in sintering (powder metallurgy) the process compresses a volume of metal powder at such high pressures and temperatures, that through a combination of deformation, creep and diffusion bonding you actually create a product with an homogenous annealed microstructure (compact solid) with minimal or no impurities in the material.
HIP gives the manufacturer and ultimate user a number of unique benefits:
- Highest Achievable Density
- Higher Static Strength
- No segregation or grain growth during manufacture
- Higher Dynamic / yield and tensile strength
- Homogeneous annealed microstructure
- Maximum abrasion resistance
- Higher Corrosion resistance
- Reduced porosity
- Improved fatigue resistance
- Reduction of Microshrinkage of castings
- Near-Net shaped parts