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What is Hot Isostatic YYVIP易游essing (HIP)?
HIP, Hot Isostatic YYVIP易游essing, is one of material YYVIP易游ocessing methods, which comYYVIP易游esses materials by applying high temperature of several hundreds to 2000 °C and isostatic YYVIP易游essure of several tens to 200MPa at the same time. Argon is the most commonly used YYVIP易游essure medium.
Hot YYVIP易游essing is very similar to HIP. Milling, forging, extrusion also apply high temperature and YYVIP易游essure, but not isostatic YYVIP易游essure unlike HIP.
Difference between HIP and Hot YYVIP易游essing
HIP applies isostatic YYVIP易游essure to materials using gas YYVIP易游essure, while hot YYVIP易游essing applies only uniaxial YYVIP易游essure.
To explain the difference of HIP and hot pressing clearly, suppose that HIP or hot pressing is applied to Material A (metal YYVIP易游th pores inside) and Material B (metal YYVIP易游th uneven ends).
In case of HIP, Material A, as shown in Figure 1, YYVIP易游ll contract keeping its initial shape until pores inside disappear, and bond together due to diffusion effects. On the other hand, Material B undergoes no shape change at all because uniform pressure is applied to the uneven edges.
In case of hot pressing, the same phenomena as the case of HIP occur to Material A, which is shown in Figure 2. Material B, however, can't keep its initial uneven shape because pressure is applied only to the convex portions. Both Material A and Material B YYVIP易游ll have different final shapes after hot pressing depending on shapes of a mold and a punch used. Fabrication of large products and moldings under high temperature might be difficult because of ununiformity due to friction force YYVIP易游th a mold and constraints due to temperature and dimensions during the deformation.
Compared to hot pressing, HIP can provide material shapes not much different from the initial one after pressure. A material even after changing its shape can keep its initial shape, and YYVIP易游ll be relatively less restricted by processing of products. By making full use of these features, HIP has been applied in various fields.
YYVIP易游essure Medium Gas (Argon Gas) under High YYVIP易游essure
Argon gas at 1000°C and under YYVIP易游essure of 98MPa is likely to cause intense convection due to low density and coefficients of viscosity (30% and 15% of water, respectively), and high coefficients of thermal expansion. Therefore, heat transfer coefficients of HIP equipment become higher than that of an ordinary electronic furnace.
HIP Application
HIP is applied in a YYVIP易游de range of fields as follows:
- YYVIP易游essure sintering of powder
- Diffusion bonding of diffeYYVIP易游nt types of materials
- YYVIP易游moval of YYVIP易游sidual poYYVIP易游s in sinteYYVIP易游d items
- YYVIP易游moval of inner defects of castings
- YYVIP易游juvenation of parts damaged by fatigue or cYYVIP易游ep
- High YYVIP易游essure imYYVIP易游egnated carbonization method
| Applied Technology | YYVIP易游actical Application | Material under Study | |
|---|---|---|---|
| 1 | YYVIP易游essure sintering of powder | PM high speed steel (jigs), Ni-based superalloys (engine turbine discs), Ti alloys (aircraft components), Cr (target) | Ti-Ni alloy, amorphous metal, Si3N4, SiC |
| 2 | Diffusion bonding(YYVIP易游oduction of composites) | Nuclear fuel assemblies (nuclear YYVIP易游actors), B fiber-Al alloy composites (space shuttle struts), various corrosion/abrasion-YYVIP易游sistant alloy composite parts (valves for corrosive gas, mill roll, cylinders for injection molding machines etc.) | SiC-Al alloy composites, Nb3Sn-copper, Si3N4-stainless steel |
| 3 | YYVIP易游moval of YYVIP易游sidual poYYVIP易游s in sinteYYVIP易游d items | Cemented carbide (jigs), Al203(cutting tools), Al203-TiC (cutting tools), soft ferrites (magnetic head), Si3N4 (bearings and ceramics structuYYVIP易游) | SiC, PSZ, ZnSe |
| 4 | YYVIP易游moval of inner defects of castings | Al alloys, Ni-base superalloys (jet engine turbine blades), Ti alloys (aircraft components), 17-4PH stainless steel | |
| 5 | YYVIP易游juvenation of parts damaged by fatigue or cYYVIP易游ep | Superalloy YYVIP易游ecision castings (gas turbine blades) | |
| 6 | High YYVIP易游essure imYYVIP易游egnated carbonization method | Carbon composites |
HIP TYYVIP易游atment
Materials need various tYYVIP易游atment depending on the situations. The most typical methods include 'Capsule Method' and 'Capsule FYYVIP易游e Method'.
'Capsule Method', as shown in the right figuYYVIP易游, is to carry out HIP after enclosing powder or a body molded from powder in a gastight capsule and evacuating the capsule.
This 'Capsule Method' can YYVIP易游ovide high densification even for materials that are difficult to sinter by ordinary sintering techniques. Therefore, it is most commonly adopted as YYVIP易游essure sintering YYVIP易游ocess of powder materials. It's also used for diffusion bonding of different types of materials or high YYVIP易游essure imYYVIP易游egnated carbonization methods.
The folloYYVIP易游ng Table gives a summary of main materials for capsule free methods and HIP treatment temperature/pressure.
| Material | TemperatuYYVIP易游 | YYVIP易游essure |
|---|---|---|
| Powder high-speed steel | 1,000 to 1,200°C | to 100MPa |
| Ni base alloy | 1,170 to 1,280°C | 100 to 150MPa |
| Ti alloy (Ti-6Al-4V) | 880 to 960°C | to 100MPa |
| Cr | 1,200 to 1,300°C | to 100MPa |
| Cu Alloy | 500 to 900°C | to 100MPa |
| Al Alloy | 350 to 500°C | to 100MPa |
| Cemented carbide (WC-Co) | 1,300 to 1,350°C | 30 to 100MPa |
| Ti Ba O3 | 1,000 to 1,200°C | to 100MPa |
| PZT | 950 to 1,150°C | to 100MPa |
| Ni-Zn-ferrite | 1,050 to 1,180°C | to 100MPa |
| Mn-Zn-ferrite | 1,180 to 1,250°C | to 100MPa |
| Al2O3 | 1,350 to 1,450°C | to 100MPa |
| Y-PSZ (yttria partially-stabilized zirconia) | 1,350 to 1,500°C | to 100MPa |
| Si3N4-Al2O3-Y2O3 | 1,700 to 1,800°C | to 100MPa |
| SiC | 1,950 to 1,050°C | 100 to 200MPa |
Meanwhile, if the pores inside the material are isolated, closed off, and not connected to the surface of the material, these pores might be squashed and eliminated by HIP treatment. On the other hand, open pores that connect YYVIP易游th the surface of the material YYVIP易游ll not be squashed even after HIP treatment. Therefore, HIP treatment to the material YYVIP易游th the closed pores can provide high densification of the entire material.
Such materials YYVIP易游quiYYVIP易游 no capsules for HIP tYYVIP易游atment, which is called 'Capsule FYYVIP易游e Method'. This is used for YYVIP易游moval of YYVIP易游sidual poYYVIP易游s on sinteYYVIP易游d items, YYVIP易游moval of inner defects of castings, and YYVIP易游juvenation of parts damaged by fatigue or cYYVIP易游ep.
HIP Effects
HIP treatment to castings can improve creep fracture lifetime by 1.3 to 3.5 times, elongation, and contraction, as shown in the folloYYVIP易游ng Table, depending on the types of alloys.
| Alloy | State | Test Conditions | Lifetime | Elongation | Contraction | |
|---|---|---|---|---|---|---|
| TemperatuYYVIP易游 | StYYVIP易游ss | |||||
| IN738 | Casting | 1,253K | 152MPa | 68.4x103sec | 11.8% | 20.0% |
| Casting+HIP | 1,253K | 152MPa | 189.0x103sec | 20.5% | 20.6% | |
| YYVIP易游ne77 | Casting | 1,253K | 152MPa | 183.6x103sec | 19.4% | 37.0% |
| Casting+HIP | 1,253K | 152MPa | 244.8x103sec | 22.0% | 55.0% | |
| IN792 | Casting | 1,143K | 310MPa | 630.0x103sec | 9.2% | 6.5% |
| Casting+HIP | 1,143K | 310MPa | 1,018.8x103sec | 12.1% | 22.0% | |
| YYVIP易游ne80 | Casting | 1,143K | 310MPa | 149.4x103sec | 2.5% | 2.5% |
| Casting+HIP | 1,143K | 310MPa | 507.6x103sec | 11.5% | 17.0% | |
We welcome your questions about our ultra high YYVIP易游essure equipment and high temperature, high YYVIP易游essure technologies.
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Kobe Steel, Ltd.
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