years later. From those early days to the


modern-day equipment, the process is synonymous with the manufacture of high-performance components.


What is HIPing? The Hot Isostatic Press (HIP) consists of a water-cooled pressure vessel with


an internal electrically heated


furnace. Argon gas is compressed into the pressure vessel whilst the furnace is heated. Components inside the HIP are subjected to combined temperature (300-2200 °C) and pressure (50-200 MPa). Under these conditions, the gas behaves as a supercritical fluid and the component/materials can be effectively squeezed under isostatic compression whilst still maintaining their original geometry. This results in HIPing being able to significantly improve the mechanical properties of the parts, by healing voids, thus eliminating defects. It can also be used


to consolidate


encapsulated metal and ceramic powders. Moreover, through HIPing, as per the


original invention, dissimilar materials can be bonded together to manufacture unique, value added components. For example, having a hard-wearing material onto a base material having greater ductility or higher thermal conductivity or lower cost.


In summary the main applications of HIPing are:


• Pore/defect elimination of solids • Consolidation of powder • Diffusion bonding of dissimilar materials


The mechanisms by which this is ®


achieved is through plastic deformation, creep and diffusion.


Applications The growing usage of HIPing on large production scale is due to the need for higher mechanical performance and defect free components in critical applications, as a consequence of extensive and still growing usage of Aluminum, Titanium, Nickel and CoCr alloys in key applications such as aerospace, orthopedic implants, and defense applications. The


towards


Aerospace industry pushes the


production of aircrafts


with reduced operating costs through an extended service life, better fuel efficiency, and increased payload and flight range. In this regard there is an increasing demand of new materials and/or materials with improved characteristics to reduce the weight of mechanical components and improve their high temperature performance in an effort to decrease fuel consumption. No matter the production method of these components, they are safety critical and need to be defect free as lives depend on their integrity. The HIPing process helps to minimize or eliminate internal defects that could, otherwise, grow under high cyclic loads and lead to catastrophic failure. The Orthopedic Industry, implant market has witnessed a meteoric rise over the past few years, mainly due to the rising number of replacement surgeries like hip, knee, shoulder, and other joints or bones. The increased incidences of orthopedic diseases and injuries and the rapid growth in the aging population are some of the growth stimulants of the orthopedic implants


market. The world population of over 60 years is anticipated to at least double from 12% to 24% from 2015 to 2050. And ironically, with a more sport active younger generation and professional athletes, the number requiring some form of implant will be in the order of 1 in 4. In the USA alone, 1.2 million football players are anticipated to be requiring orthopedic implants. Additional to this, 53 million people in the USA will suffer from osteoporosis. Similar trends can be seen in Europe and the rest of the world. Implants


present apparently


contradictory qualities such as stiffness yet have impact resistant, high fatigue life and, ideally lightness. Apart from these mechanical properties, the material must also be biologically stable. The most commonly implanted metals used in orthopedic implants are cobalt/ chrome, stainless steel, and titanium alloys, more specialized implants use Zirconium or ceramics. By definition the composition of the alloys contain small amounts of other elements. Some of these minor elements such as nickel show hypersensitivity in some patients. In those cases, Titanium alloys are the preferred choice for it bio-compatibility. Whether the parts are made via Precision Casting, Metal Injection Molding, Additive Manufacturing such as 3D printing, they still need to go through a HIPing process to eliminate defects to enable the component to realize its full potential of the mechanical properties without early failure which would cause further trauma to the patient. The presence of a dependable and accessible HIPing capability is crucial for any Industrial District wanting to be successful in the manufacturing of these high-tech components and assemblies.


January 2021 ❘ 27


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