Hot Isostatic Pressing

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Hot Isostatic Pressing Hot Isostatic Pressing Topics Covered

Topics Covered

Background

The HIP’ing Process

Advantages of HIP’ed Materials

HIP and Maching

What Type of Things can be Produced by HIP’ing?

What HIP’ing can be used for

Cladding

Areas where HIP’ing is Utilised

HIP in the Gas Turbine Industry

HIP vs Conventional Foundry Technology

Summary

Summary Background Background

In 1976, Howmet Corporation became

In 1976, Howmet Corporation became the first company to offer hot isostatic pressingthe first company to offer hot isostatic pressing (HIP) services to the aerospace industry. The HIP process, which subjects a

(HIP) services to the aerospace industry. The HIP process, which subjects a component tocomponent to elevated temperatures and pressures to eliminate internal microshrinkage, helped

elevated temperatures and pressures to eliminate internal microshrinkage, helped engineers respond to the aerospace

engineers respond to the aerospace industry’s increasingly striindustry’s increasingly stringent regulations. HIPngent regulations. HIP enabled engineers to design

enabled engineers to design components so they could meet specifications for use incomponents so they could meet specifications for use in critical, highly stressed applications.

critical, highly stressed applications. The HIP’ing Process

The HIP’ing Process

The HIP process provides a method

The HIP process provides a method for producing components from diverse powderedfor producing components from diverse powdered materials, including metals and ceramics. During the manufacturing

materials, including metals and ceramics. During the manufacturing process, a powder process, a powder mixture of several elements is placed in a

mixture of several elements is placed in a container, typically a steel can. The container, typically a steel can. The container iscontainer is subjected to elevated temperature and a very high vacuum to remove air and moisture subjected to elevated temperature and a very high vacuum to remove air and moisture from the powder. The con

from the powder. The container is then sealed and HIP’ed The tainer is then sealed and HIP’ed The application of high inertapplication of high inert gas pressures and elevated temperatures results in the removal

gas pressures and elevated temperatures results in the removal of internal voids andof internal voids and creates a strong metallurgical bond throughout the material. The result is a clean creates a strong metallurgical bond throughout the material. The result is a clean homogeneous material with a uniformly fine grain size and a near 100% density. homogeneous material with a uniformly fine grain size and a near 100% density. Advantages of HIP’ed Materials

Advantages of HIP’ed Materials

The reduced porosity of HIP’ed materials enables improved mechanical

The reduced porosity of HIP’ed materials enables improved mechanical properties andproperties and increased workability. The HIP process eliminates internal voids and creates clean, firm increased workability. The HIP process eliminates internal voids and creates clean, firm

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bonds and fine, uniform microstructures. These characteristics are not po

bonds and fine, uniform microstructures. These characteristics are not po ssible withssible with welding or casting. The virtual elimination of internal

welding or casting. The virtual elimination of internal voids enhances part performancevoids enhances part performance and improves fatigue strength. The process also

and improves fatigue strength. The process also results in significantly improved non-results in significantly improved non-destructive examination ratings.

destructive examination ratings. HIP and Maching

HIP and Maching

One of the primary advantages of the HIP process is its ability to create near-net shapes One of the primary advantages of the HIP process is its ability to create near-net shapes that require little machining. Conventional manufacturing methods

that require little machining. Conventional manufacturing methods use only 10-30% of use only 10-30% of the material purchased in the final p

the material purchased in the final product the rest is removed during machining. roduct the rest is removed during machining. AA HIP’ed near-net shape part typically uses 80-90% of the pu

HIP’ed near-net shape part typically uses 80-90% of the pu rchased material. As a result,rchased material. As a result, machining time and costs are significantly reduced. The

machining time and costs are significantly reduced. The strong combination of improvedstrong combination of improved raw material use and greater machining efficiency that results from the HIP process has raw material use and greater machining efficiency that results from the HIP process has driven the growth of HIP’ed powder metal

driven the growth of HIP’ed powder metal parts manufactured from nickel-based andparts manufactured from nickel-based and titanium alloys. In fact, HIP has become the

titanium alloys. In fact, HIP has become the standard ‘bill of material’ on virtually allstandard ‘bill of material’ on virtually all powder metal components produced by Howmet’s HIP operation.

powder metal components produced by Howmet’s HIP operation. What Type of Things can

What Type of Things can be Produced by HIP’ing?be Produced by HIP’ing?

The HIP process enables engineers to produce materials of all shapes and sizes, including The HIP process enables engineers to produce materials of all shapes and sizes, including cylindrical billets, flat rectangular bar billets, solid shapes with complex external

cylindrical billets, flat rectangular bar billets, solid shapes with complex external

geometry, and complex shapes with internal cavities. Because powder metals do not have geometry, and complex shapes with internal cavities. Because powder metals do not have the directional property characteristics of forgings, the HIP process can produce materials the directional property characteristics of forgings, the HIP process can produce materials from metallic compositions that are difficult or impossible to forge or cast. Howmet’s from metallic compositions that are difficult or impossible to forge or cast. Howmet’s expertise in HIP powder compaction is displayed in

expertise in HIP powder compaction is displayed in the manufacture of abrasive tips,the manufacture of abrasive tips, figure 1. Abrasive tips are uniquely layered compacts

figure 1. Abrasive tips are uniquely layered compacts of ceramic and metallic powdersof ceramic and metallic powders which are used for turbine blade wear protection.

which are used for turbine blade wear protection.

Figure 1.

Figure 1. Ceramic and metal sides of finish machined Ceramic and metal sides of finish machined abrasive tipsabrasive tips What HIP’ing can be used for

What HIP’ing can be used for

The HIP process is now not only used for densifying castings, but in many other The HIP process is now not only used for densifying castings, but in many other applications such as diffusion bonding of

applications such as diffusion bonding of dissimilar materialdissimilar materials, component repair ans, component repair andd powder metal consolidation. In the powder metal market, Howmet applies HIP

powder metal consolidation. In the powder metal market, Howmet applies HIP technology in four separate areas:

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•

• Consolidation of powder metals (PM)Consolidation of powder metals (PM)

•

• Creation of PM shapesCreation of PM shapes

•

• Production of near-net shapesProduction of near-net shapes

•

• Cladding.Cladding.

Cladding Cladding

Another fundamental application of the

Another fundamental application of the HIP process is cladding. Cladding is the selectiveHIP process is cladding. Cladding is the selective bonding of hardfacing materials onto va

bonding of hardfacing materials onto various substrate surfaces. A less expensiverious substrate surfaces. A less expensive material is coated with a thin layer of

material is coated with a thin layer of powdered metal, creating a buffer on powdered metal, creating a buffer on its wear its wear surface. This reduces costs by placing exp

surface. This reduces costs by placing expensive, wear resistant materials only whereensive, wear resistant materials only where they are needed. As a

they are needed. As a result, wear resistant properties are improved without incurringresult, wear resistant properties are improved without incurring unnecessary cost penalties. An additional benefit of

unnecessary cost penalties. An additional benefit of cladding is that it can create bcladding is that it can create bondsonds between otherwise incompatible materials such as metal, intermetallic, and

between otherwise incompatible materials such as metal, intermetallic, and ceramicceramic powders.

powders.

Most notably, cladding is used in the production of diesel engine valve lifters, figure 2. Most notably, cladding is used in the production of diesel engine valve lifters, figure 2. Here, the hardfacing material (tungsten carbide) is bonded to a lower cost material such Here, the hardfacing material (tungsten carbide) is bonded to a lower cost material such as an alloy steel. Howmet has also

as an alloy steel. Howmet has also used this capability in a number of other used this capability in a number of other industries,industries, such as the offshore and

such as the offshore and plastic extrusion equipment industries, where cladding is used toplastic extrusion equipment industries, where cladding is used to fortify various components including valve bodies, thick wall

fortify various components including valve bodies, thick wall casings, and compoundcasings, and compound tubes, figure 2.

tubes, figure 2.

Figure 2.

Figure 2. Left, diesel engine valve lifters with HIP clad carbide hardfacing Left, diesel engine valve lifters with HIP clad carbide hardfacing and right,and right, cross section of 4140 steel extrusion barrel with HIP clad inside

cross section of 4140 steel extrusion barrel with HIP clad inside diameter of nickeldiameter of nickel alloy hardfacing.

alloy hardfacing. Areas where HIP’ing is Utilised

Areas where HIP’ing is Utilised

Today, HIP has expanded well beyond aerospace products and is finding new Today, HIP has expanded well beyond aerospace products and is finding new

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applications in a range of

applications in a range of industries, including automotive (turbocharger wheels andindustries, including automotive (turbocharger wheels and diesel engine valve lifters), medical (prosthetic devices), petroleum (valve

diesel engine valve lifters), medical (prosthetic devices), petroleum (valve bodies) andbodies) and chemical processing. HIP offers engineers in these industries greater design freedom than chemical processing. HIP offers engineers in these industries greater design freedom than was previously possible with conventional processes such as forging and casting. Parts was previously possible with conventional processes such as forging and casting. Parts which cannot be made by the more conventional processes are now possible using HIP, which cannot be made by the more conventional processes are now possible using HIP, figure 3. An example of

figure 3. An example of this is the dual alloy wheel. In this the this is the dual alloy wheel. In this the hub, which is made of ahub, which is made of a HIP consolidated powder metal, is bonded

HIP consolidated powder metal, is bonded to a cast outer ring through the to a cast outer ring through the use of the HIPuse of the HIP process. The resulting part has excellent tensile properties in the

process. The resulting part has excellent tensile properties in the hub and high stresshub and high stress rupture properties on the outer ring.

rupture properties on the outer ring.

Figure 3.

Figure 3. A Selection of parts made by HIP’ingA Selection of parts made by HIP’ing HIP in the Gas Turbine Industry

HIP in the Gas Turbine Industry A rapid rise in the use

A rapid rise in the use of the HIP process followed the intensification of standards withinof the HIP process followed the intensification of standards within the gas turbine industry. These standards required the elimination of shrinkage porosity in the gas turbine industry. These standards required the elimination of shrinkage porosity in investment cast components, such as increasingly complex airfoils.

investment cast components, such as increasingly complex airfoils. HIP vs Conventional Foundry Technology

HIP vs Conventional Foundry Technology Conventional foundry technology was not u

Conventional foundry technology was not up to the task. By developing p to the task. By developing HIP, HowmetHIP, Howmet met mechanical property requirements and eliminated shrinkage

met mechanical property requirements and eliminated shrinkage porosity defects. HIPporosity defects. HIP provided the means to produce the desired high density, fine grain material.

provided the means to produce the desired high density, fine grain material. Summary

Summary

Since it’s inception in 1955, the

Since it’s inception in 1955, the use of the HIP has grown steadily in the pouse of the HIP has grown steadily in the powder metalwder metal and casting densification fields. During the last 25 years, HIP has become a proven and casting densification fields. During the last 25 years, HIP has become a proven process in the production of aerospace

process in the production of aerospace and industrial gas turbine parts, and the futureand industrial gas turbine parts, and the future looks bright. New markets have developed for rocket engines, satellites and aerospace looks bright. New markets have developed for rocket engines, satellites and aerospace airframe castings. HIP continues to be used more

airframe castings. HIP continues to be used more frequently in the production of powder frequently in the production of powder metal parts and shapes. Cladding and near net shape technology are on the rise with metal parts and shapes. Cladding and near net shape technology are on the rise with significant growth expected in the production of sputtering targets. As with any significant growth expected in the production of sputtering targets. As with any technology, awareness by industry is the key to growth.

technology, awareness by industry is the key to growth. With this in mind, a HIP councilWith this in mind, a HIP council was recently formed consisting of equipment manufacturers and HIP suppliers. The was recently formed consisting of equipment manufacturers and HIP suppliers. The inaugural meeting of the Hot

inaugural meeting of the Hot Isostatic Pressing Council of the Advanced ParticulateIsostatic Pressing Council of the Advanced Particulate Materials Association took place on 30 August, 1999 at Bodycote IMT, Andover, Materials Association took place on 30 August, 1999 at Bodycote IMT, Andover, Massachusettes. This council will now address the areas of

Massachusettes. This council will now address the areas of safety, marketing andsafety, marketing and technology, to further enhance the

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Primary author: Steven Mussman Primary author: Steven Mussman

Source: Materials World Vol. 7 no. 11, pp. 677-78, November 1999. Source: Materials World Vol. 7 no. 11, pp. 677-78, November 1999.

For more information on Materials World please visit

For more information on Materials World please visit The Institute of The Institute of

Materials

Materials..

Hot Isostatic Pressing (HIP) is a Hot Isostatic Pressing (HIP) is a method by which a workpiece is method by which a workpiece is processed under the simultaneous processed under the simultaneous

application of high isostatic application of high isostatic pressure gas like argon, generally pressure gas like argon, generally

over 98MPa(1000kgf/cm

over 98MPa(1000kgf/cm22), and), and high-temperature, generally over high-temperature, generally over 1000

1000ﾁﾁ_C._C.

HIP is an indispensable process of HIP is an indispensable process of manufacturing for industries such manufacturing for industries such as sintered hard alloys, ceramics as sintered hard alloys, ceramics and super alloys, and a prospective and super alloys, and a prospective technology which fill the requests technology which fill the requests of the coming generations in which of the coming generations in which high-value added products will be high-value added products will be more and more in demand.

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Production technology Production technology

Daido steel offers the diversity of manufacturing equipment and high-caliber Daido steel offers the diversity of manufacturing equipment and high-caliber production technology supplying high-quality target materials and evaporation production technology supplying high-quality target materials and evaporation

materials which only a general specialty steel manufacturer can offer. materials which only a general specialty steel manufacturer can offer.

E B F (

E B F ( Electron-beam Melting Furnace )Electron-beam Melting Furnace ) Features

Features

Water-cooled copper mold remelting Water-cooled copper mold remelting lamination solidification

lamination solidification under highly vacuum state under highly vacuum state

Melting atmospheric pressure Melting atmospheric pressure

10-10 Torr 10-10 Torr Melting materials Melting materials High melting-point High melting-point metalic(Nb,Mo,Ta,W) metalic(Nb,Mo,Ta,W)

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V I F ( Vacuum Induction Melting ) V I F ( Vacuum Induction Melting )

Features Features

Refractory crucible melting under Refractory crucible melting under vacuum state

vacuum state

-10 Torr -10 Torr

Melting materials Melting materials

High-grade specialty steel, super High-grade specialty steel, super alloy

alloy

V A F ( Vacuum Arc Melting Furnace ) V A F ( Vacuum Arc Melting Furnace )

Features Features

Water-cooled copper mold remelting Water-cooled copper mold remelting lamination solidification under vacuum lamination solidification under vacuum state melting atmospheric pressure state melting atmospheric pressure

-10 Torr -10 Torr

High-grade specialty steel, High-grade specialty steel, super alloy (Ti, Zr)

super alloy (Ti, Zr)

P S C F ( Plasma Skull Casting Furnace ) P S C F ( Plasma Skull Casting Furnace )

Features Features

Uncontaminated melting of Uncontaminated melting of granulated

granulated

material in skull material in skull

(Remelting of rod materials is a (Remelting of rod materials is alsolso

possible) possible)

760 Torr (Ar, regulated 760 Torr (Ar, regulated atmosphere)

atmosphere)

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Special metals, Alloy materials, Special metals, Alloy materials, Reactive metals (Ti, Zr, Cr) Reactive metals (Ti, Zr, Cr)

P P C F ( Plasma Progressive Casting Furnace ) P P C F ( Plasma Progressive Casting Furnace )

Features Features

Melting of granulated material in Melting of granulated material in water-cooled copper mold

water-cooled copper mold

760 Torr (Ar) 760 Torr (Ar)

Reactive metals (Ti, Zr) Reactive metals (Ti, Zr)

H P

H P ( Hot ( Hot Press )Press ) Features Features

Sintering of powder in high temperature Sintering of powder in high temperature

Temperature Temperature 2,000 °C max. 2,000 °C max. Atmosphere Atmosphere Vacuum, Ar 1 atmosphere Vacuum, Ar 1 atmosphere Pressure Pressure 250 kg/cm max. 250 kg/cm max. Processed materials Processed materials

W-Si, Mo-Si, Tb-Fe-Co W-Si, Mo-Si, Tb-Fe-Co

H I P ( Hot Isostatic Press ) H I P ( Hot Isostatic Press )

Features Features

Isostatic pressing in high temperature Isostatic pressing in high temperature

Temperature Temperature 2,000 °C max. 2,000 °C max. Atmosphere Atmosphere Vacuum, Ar 1 atmosphere Vacuum, Ar 1 atmosphere Pressure Pressure 2,000 kg/cm max. 2,000 kg/cm max. Processed materials Processed materials

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Cr, Cr-Alloy Cr, Cr-Alloy

Hot Isostatic Pressing Hot Isostatic Pressing

It may sound like some new, exotic dry cleaning process and though many have heard of It may sound like some new, exotic dry cleaning process and though many have heard of "HIP", Hot Isostatic Pressing, few of us understand the many benefits of this materials "HIP", Hot Isostatic Pressing, few of us understand the many benefits of this materials process. Since it's largely misunderstood, many conservative engineers are reluctant to process. Since it's largely misunderstood, many conservative engineers are reluctant to

adopt HIPping as an element

adopt HIPping as an element in their manufacturing designs, thus missing a valuablein their manufacturing designs, thus missing a valuable process tool.

process tool.

HIP is a process that subjects a material simultaneously to both high

HIP is a process that subjects a material simultaneously to both high temperature andtemperature and high gas pressure, usually Argon, in vessels equipped

high gas pressure, usually Argon, in vessels equipped with sophisticated control systemswith sophisticated control systems and telemetry.

and telemetry.

Typically, the temperature is selected to permit limited plastic deformation of the Typically, the temperature is selected to permit limited plastic deformation of the

material being processed in the solid state at an argon gas pressure of 15,000, 30,000, or material being processed in the solid state at an argon gas pressure of 15,000, 30,000, or at times, 45,000 psi (1,000

at times, 45,000 psi (1,000 to 3,000 atmospheres) is isostatically exerted on the heatedto 3,000 atmospheres) is isostatically exerted on the heated parts for a period of time. The

parts for a period of time. The chamber is then slowly cooled, depressurized and chamber is then slowly cooled, depressurized and the partsthe parts removed.

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(Figure 1. Typical HIP schematic.) (Figure 1. Typical HIP schematic.)

Since modern HIP chambers tend to

Since modern HIP chambers tend to be very large, huge multiples of small parts can bbe very large, huge multiples of small parts can b ee accommodated in a single

accommodated in a single HIPping run, thus rendering the unit cost of the HIPping run, thus rendering the unit cost of the process to aprocess to a small number.

small number.

HIP can close internal porosity in a material without distorting external geometry, HIP can close internal porosity in a material without distorting external geometry, consolidate powder materials to 100% of theoretical density or form perfect diffusion consolidate powder materials to 100% of theoretical density or form perfect diffusion bonds between

bonds between similar or dissimilar materials.similar or dissimilar materials.

All raw materials contain microscopic voids and "bubbles" of gas, from that standpoint, All raw materials contain microscopic voids and "bubbles" of gas, from that standpoint, all raw materials can be considered p

all raw materials can be considered porous. The advantages of HIP for such orous. The advantages of HIP for such porousporous materials include the elimination of all internal porosity in simple or complex

materials include the elimination of all internal porosity in simple or complex shapes withshapes with resulting improvement of mechanical properties such as du

resulting improvement of mechanical properties such as du ctility and fatigue life.ctility and fatigue life. The HIP process falls into three categories: Densification, Powder Metallurgy and The HIP process falls into three categories: Densification, Powder Metallurgy and Composites, diffusing two like, or unlike metals together.

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The benefits for powder materials include the

The benefits for powder materials include the ability to produce 100% dense billets andability to produce 100% dense billets and powdered metal near-net shapes at relatively low cost because of the reduction in

powdered metal near-net shapes at relatively low cost because of the reduction in machining costs. Near net shapes can be pressed to 100% density, Shape control is machining costs. Near net shapes can be pressed to 100% density, Shape control is obtained by cans and

obtained by cans and mandrels designed using both CAD and mandrels designed using both CAD and FEA programs. SmallFEA programs. Small variations in packing density lead to small distortions in the

variations in packing density lead to small distortions in the final shape. Mating surfaces,final shape. Mating surfaces, for instance, will almost always have to be

for instance, will almost always have to be machined. HIP can also achieve machined. HIP can also achieve 100%100% diffusion bonds in clad composite materials.

diffusion bonds in clad composite materials.

Advantages

The decision to employ hard chromium plating would be dictated by the following needs The decision to employ hard chromium plating would be dictated by the following needs and requirements:

and requirements: 1.

1. CoContntrorol of mil of micrcrosostrtrucuctuturere 2.

2. HigHigher cher contontent ent of aof allolloyinying elg elemeementsnts 3.

3. HiHigh gh mamateteririal al purpuritityy 4.

4. NeaNear ner net sht shape ape comcomponeponents nts up tup to 12,o 12,000 000 kgkg 5.

5. ComCompleplex capx capsulsule and e and matmaterierial deal desigsignn

Typical HIP products now include automotive parts, pump

Typical HIP products now include automotive parts, pump bodies, valves, vacuumbodies, valves, vacuum chambers, bearings, sterile enclosures, etc. anywhere residual porosity causes high chambers, bearings, sterile enclosures, etc. anywhere residual porosity causes high rejection rates, unacceptable property levels and

rejection rates, unacceptable property levels and surface finishing problems after surface finishing problems after machining. Commercial alloy applications include steel, stainless steel and aluminum machining. Commercial alloy applications include steel, stainless steel and aluminum castings. Not limited to metals, the process is very versatile, having

castings. Not limited to metals, the process is very versatile, having been used to densifybeen used to densify ceramics, plastics, glasses and many other materials.

ceramics, plastics, glasses and many other materials. Many design engineers will avoid the u

Many design engineers will avoid the use of low-cost castings in applications that requirese of low-cost castings in applications that require the freedom from porosity, for example for high-vacuum surfaces or

the freedom from porosity, for example for high-vacuum surfaces or containers, for containers, for surfaces that need to be

surfaces that need to be antiseptically cleanable, or for fatigue-critical applications. Theyantiseptically cleanable, or for fatigue-critical applications. They need to know that

need to know that a HIP densified casting is a very cost-effective alternative to machininga HIP densified casting is a very cost-effective alternative to machining parts from a wrought blank.

parts from a wrought blank.

Material densification via the HIP process, densifies to the material's theoretical limit. Material densification via the HIP process, densifies to the material's theoretical limit. This has several advantages including, improvement of mechanical properties,

This has several advantages including, improvement of mechanical properties,

enhancement of physical assets and ease of manufacturing. Typical applications have enhancement of physical assets and ease of manufacturing. Typical applications have been for fatigue-critical applications like nickel and

been for fatigue-critical applications like nickel and titanium alloy structural castings for titanium alloy structural castings for jet engines, turbine blades and

jet engines, turbine blades and vanes, and cast cobalt-chromium or titanium alloyvanes, and cast cobalt-chromium or titanium alloy orthopedic implants, such as hip joints.

orthopedic implants, such as hip joints.

The HIP process allows for the manufacture of composite or dissimilar materials, thus The HIP process allows for the manufacture of composite or dissimilar materials, thus avoiding welds or costly, gasketed assemblies. The

avoiding welds or costly, gasketed assemblies. The same high temperature and pressuressame high temperature and pressures may be applied to achieve the diffusion bonding of encapsulated metal powder to a solid may be applied to achieve the diffusion bonding of encapsulated metal powder to a solid material or the diffusion bonding of different solid materials. Thereby providing for the material or the diffusion bonding of different solid materials. Thereby providing for the combination of properties such as a

combination of properties such as a stainless steel body diffusion bonded to a titaniumstainless steel body diffusion bonded to a titanium nozzle that is nearly free from residual stresses.

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(Figure 1. Diesel engine

(Figure 1. Diesel engine valve lifter.)valve lifter.)

For some material combinations, an interlayer is required to prevent

For some material combinations, an interlayer is required to prevent brittle phasebrittle phase transformation or to minimize thermal expansion differences between materials for transformation or to minimize thermal expansion differences between materials for bonding.

bonding.

The diesel engine valve lifter shown in figure two is a good example of a clad product. The diesel engine valve lifter shown in figure two is a good example of a clad product. This product replaced a troublesome design that used furnace brazing to apply a tungsten This product replaced a troublesome design that used furnace brazing to apply a tungsten carbide wafer to a steel lifter body. The HIP bonded valve lifter proved to be significantly carbide wafer to a steel lifter body. The HIP bonded valve lifter proved to be significantly more reliable and saved a

more reliable and saved a substantial amount of money in scrap and substantial amount of money in scrap and repairs. In total, inrepairs. In total, in the past five years Bodycote-IMT of Andover, MA reports that they have produced well the past five years Bodycote-IMT of Andover, MA reports that they have produced well over 3 million lifters without a single field failure.

over 3 million lifters without a single field failure.

Hot isostatic pressing can provide many benefits by stabilizing a material, removing Hot isostatic pressing can provide many benefits by stabilizing a material, removing residual stresses, densifying and eliminating voids and occlusions. The process residual stresses, densifying and eliminating voids and occlusions. The process

"homogenizes" an alloy and in most cases, the properties of the material are enhanced, "homogenizes" an alloy and in most cases, the properties of the material are enhanced, providing greater stability and wear characteristics.

providing greater stability and wear characteristics.

With cast materials, parts can be cast to near net shape and HIP'd, thus eliminating costly With cast materials, parts can be cast to near net shape and HIP'd, thus eliminating costly machining and additional machining stresses. A good example would be aluminum machining and additional machining stresses. A good example would be aluminum castings, notoriously thermally unstable to the point where producing a

castings, notoriously thermally unstable to the point where producing a cast aluminumcast aluminum mirror was once considered virtually impossible.

mirror was once considered virtually impossible. However, a large 12"

However, a large 12" flat stabilization mirror is being used in the fire control system of flat stabilization mirror is being used in the fire control system of the FVS Bradley tracked vehicle. Originally, a thick, 6

the FVS Bradley tracked vehicle. Originally, a thick, 6 061-aluminum alloy blank was061-aluminum alloy blank was heavily machined and ribbed in order to provide light weighting of the backside of the heavily machined and ribbed in order to provide light weighting of the backside of the mirror. More material ended up in chips

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effort to reduce costs, a cast aluminum mirror of

effort to reduce costs, a cast aluminum mirror of A-201 alloy was produced. The mirror A-201 alloy was produced. The mirror blank was HIP'd and the on

blank was HIP'd and the only post machining required was for the two mirror trunnions.ly post machining required was for the two mirror trunnions. The mirror face was subsequently diamond fly-cut to an

The mirror face was subsequently diamond fly-cut to an optical surface. Beingoptical surface. Being theoretically dense, there were no voids o

theoretically dense, there were no voids or occlusions to mar the optical surface.r occlusions to mar the optical surface. The final cast and HIP'd mirror proved to

The final cast and HIP'd mirror proved to be far more thermally stable than it's machinedbe far more thermally stable than it's machined counterpart. In addition, this material processing reduced the final production mirror cost counterpart. In addition, this material processing reduced the final production mirror cost by more than 30%.

by more than 30%.

Beryllium and titanium are both sintered materials and both

Beryllium and titanium are both sintered materials and both are extremely difficult toare extremely difficult to machine.

machine.

(Table 1. These tensile properties show the difference between treated and untreated and

(Table 1. These tensile properties show the difference between treated and untreated and HIP tensile barsHIP tensile bars from 7 x

from 7 x 7 3/4 in permanent mold 7 3/4 in permanent mold plates of several different aluminum alloys.)plates of several different aluminum alloys.)

Beryllium is not only a costly material but it is also prone to

Beryllium is not only a costly material but it is also prone to micro-cracking or micro-cracking or "twinning" during the machining process. Final d

"twinning" during the machining process. Final dimensions require extremely carefulimensions require extremely careful machining with very small cuts of .0005".

machining with very small cuts of .0005". This is followed by an acid etch, This is followed by an acid etch, hopefully, tohopefully, to final dimensions. By HIP'ing beryllium powders to near-net shape, high machining

final dimensions. By HIP'ing beryllium powders to near-net shape, high machining costs,costs, are thus eliminated and the

are thus eliminated and the process radically enhances the properties of the material.process radically enhances the properties of the material. The highly and oft misstated toxic effects of beryllium aside, HIP'ing Be

The highly and oft misstated toxic effects of beryllium aside, HIP'ing Be to near netto near net shape greatly reduces the final cost of

shape greatly reduces the final cost of a part made from this remarkably strong anda part made from this remarkably strong and lightweight, material.

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Cast Titanium aircraft engine parts are routinely HIP'd for greater reliability and Cast Titanium aircraft engine parts are routinely HIP'd for greater reliability and performance. Today's jet engines could no

performance. Today's jet engines could not function without the HIP process to densifyt function without the HIP process to densify and improve this difficult cast material.

and improve this difficult cast material.

The HIP process is recognized as a means of providing enhanced soundness or integrity, The HIP process is recognized as a means of providing enhanced soundness or integrity, increased density and improved properties to w

increased density and improved properties to w wide rane of materials. The processwide rane of materials. The process significantly improves the mechanical properties an fatigue strength aluminum alloy, significantly improves the mechanical properties an fatigue strength aluminum alloy, sand and permanent mold castings. It has proved capable of eliminating microporosity sand and permanent mold castings. It has proved capable of eliminating microporosity resulting from the precipitation of hydrogen and the

resulting from the precipitation of hydrogen and the formation of internal shrinkageformation of internal shrinkage during solidification. The HIP advantage is of importance

during solidification. The HIP advantage is of importance in the manufacture of castingsin the manufacture of castings subject to radiographic inspection when required levels of soundness are not achieved in subject to radiographic inspection when required levels of soundness are not achieved in the casting process.

the casting process.

At elevated temperatures and pressures voids formed by

At elevated temperatures and pressures voids formed by hydrogen precipitation in thehydrogen precipitation in the castings are collapsed and healed as are shrinkage voids uncontaminated by hydrogen. castings are collapsed and healed as are shrinkage voids uncontaminated by hydrogen. Mechanical densification such as forging did

Mechanical densification such as forging did not provide the same results, even atnot provide the same results, even at

elevated temperatures. Typical tensile improvements in Aluminum castings are illustrated elevated temperatures. Typical tensile improvements in Aluminum castings are illustrated in table one.

in table one.

October 1, 1999

October 1, 1999 by Fred Hochgraf by Fred Hochgraf Published October 1, 1999, in our

Published October 1, 1999, in our Nuts & Bolts, Volume 11 Nuts & Bolts, Volume 11 newsletter.newsletter.

Click here to view the

Click here to view the entire newsletter.entire newsletter.

http://nhml.com/resources/1999/10/1/hot-isostatic-pressing

http://nhml.com/index.cfm

http://nhml.com/index.cfmnew hampashire materials laboratory ltd.new hampashire materials laboratory ltd.

A hot isostatic pressing apparatus (HIP apparatus) comprises a vertically cylindrical A hot isostatic pressing apparatus (HIP apparatus) comprises a vertically cylindrical high- pressure vessel comprising a high-pressure cylinder

pressure vessel comprising a high-pressure cylinder 11 and upper and lower lidsand upper and lower lids22andand3;3;aa bottomed cylindrical casing

bottomed cylindrical casing66 capable of housing workpiecescapable of housing workpieces99and a resistance-wireand a resistance-wire heater

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formed in a bottomed cylindrical shape on the outside of the casing

formed in a bottomed cylindrical shape on the outside of the casing 66so as to cover theso as to cover the casing

casing6,6,and a heat sink and a heat sink 1717having a water cooling mechanism provided in the spacehaving a water cooling mechanism provided in the space defined by the heat insulating structure

defined by the heat insulating structure 1616and the inner surface of the high-pressureand the inner surface of the high-pressure cylinder

cylinder 1,1,which are provided within the high-pressure vessel; and a pressure mediumwhich are provided within the high-pressure vessel; and a pressure medium gas stirring fan

gas stirring fan 1212 for promoting the temperature uniformity of the space of the for promoting the temperature uniformity of the space of the treatmenttreatment chamber

chamber 77for housing the workpiecesfor housing the workpieces9,9,the stirring fan being arranged on the lower lidthe stirring fan being arranged on the lower lid 33 side within the casing

side within the casing 6,6,whereby the cooling to a temperature range of 100° C. or lower whereby the cooling to a temperature range of 100° C. or lower which allows a quenching treatment and the safe manual handling of workpieces can be which allows a quenching treatment and the safe manual handling of workpieces can be efficiently performed.

efficiently performed.

New HIP-ping method

HIP–ping by super-high pressure liquid

It is known that microscopic intergranular cavities decrease substantially the It is known that microscopic intergranular cavities decrease substantially the strength of materials. Fractures in parts usually start from these cavities. strength of materials. Fractures in parts usually start from these cavities.

The current technology for reducing this problem is by treating many critical parts The current technology for reducing this problem is by treating many critical parts by a process of Gas pressure (up to 1500ATM) integrated with high temperature by a process of Gas pressure (up to 1500ATM) integrated with high temperature (up to 1300

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“ Hot Isostatic Pressing” or “HIP-ping “ closes and seals the inter granular cavities “ Hot Isostatic Pressing” or “HIP-ping “ closes and seals the inter granular cavities

in materials (picture #1) and therefore increases their reliability. in materials (picture #1) and therefore increases their reliability.

At present, many critical parts for aircraft engines, some rocket units and etc. are At present, many critical parts for aircraft engines, some rocket units and etc. are treated by HIP-ping process.

treated by HIP-ping process.

As some heat resistant steel alloys are very fragile, they are not made by plastic As some heat resistant steel alloys are very fragile, they are not made by plastic deformation processes and they are produced by casting. Parts from such alloys, for deformation processes and they are produced by casting. Parts from such alloys, for example, blades for gas turbines, suffer from micro and macro-cavities after casting. example, blades for gas turbines, suffer from micro and macro-cavities after casting. These cavities decrease considerably strength of parts and they must by eliminate. These cavities decrease considerably strength of parts and they must by eliminate. At present, HIP-ping process is sole technological process, that can do it.

At present, HIP-ping process is sole technological process, that can do it.

“MLC Extrusion Systems” has developed an innovative method for treatment of “MLC Extrusion Systems” has developed an innovative method for treatment of materials, the “ Hot Isostatic Pressing by Liquid”, which has match technical and materials, the “ Hot Isostatic Pressing by Liquid”, which has match technical and economical advantages.

economical advantages. (see picture #2)

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The treated parts are loaded in an electric oven. The hot parts are later loaded unto The treated parts are loaded in an electric oven. The hot parts are later loaded unto the high pressure working chamber , which is located between stamps of hydraulic the high pressure working chamber , which is located between stamps of hydraulic press .

press .

It is filled with working liquid, the press stamp falls and presses the plunger It is filled with working liquid, the press stamp falls and presses the plunger creating a super high pressure (14,000-18,000 ATM) into the chamber. creating a super high pressure (14,000-18,000 ATM) into the chamber.

The loaded parts are soaked under this super high pressure for 20-60 seconds and The loaded parts are soaked under this super high pressure for 20-60 seconds and they are unloaded after cleaning the chamber by inert gas from receiver .After the they are unloaded after cleaning the chamber by inert gas from receiver .After the unloading the system is ready for another cycle. The treatment by super high unloading the system is ready for another cycle. The treatment by super high pressure allows to “close” both micro-cavities and even macro-cavities. Therefore pressure allows to “close” both micro-cavities and even macro-cavities. Therefore the quality of such “healing” process is very elevated. Moreover, energy

the quality of such “healing” process is very elevated. Moreover, energy consumption is very low due to the incompressibility of the liquid, and due to consumption is very low due to the incompressibility of the liquid, and due to

heating the parts outside the working chamber. Investment in the equipment is very heating the parts outside the working chamber. Investment in the equipment is very low, especially on availability of a hydraulic press; the technological process is

low, especially on availability of a hydraulic press; the technological process is simple, reliable, and safe and may be easily automated.

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