Powder Hot Isostatic Pressing Research Articles

The durability of iodide sodalite

An iodide sodalite wasteform has been prepared by Hot Isostatic Pressing of powder produced by hydrothermal synthesis. The wasteform was free of leachable secondary phases which can mask leaching mechanisms. Leaching is by congruent dissolution and leach rates decrease as Si and Al accumulate in the leachate. Differential normalised leach rates are 0.005–0.01gm−2d−1 during the 7–14day period. This indicates that sodalite dissolution in natural groundwater, already saturated in these elements, will be very low.

Hot isostatic pressing process simulation: application to metal powders

Deformation and transport mechanisms of matter, which intervene in the powder densification process by hot isostatic pressing (HIP), are very complicated to put into equation form. Their contribution to densification depends on powder characteristics, their configuration in aggregates, and the used HIP cycle parameters (temperature, pressure, and time). In this work, we have envisaged modifications that seemed to us necessary to bring to the previous simulations, so that their predictions will be related to experiment. New equations were established to evaluate the efficient pressure and the contributions of different mechanisms. The obtained results are used for the construction of densification diagrams by the HIP of copper, nickel, and tungsten powders and to the comparison with the experimental data. The comparative tables, between theoretical results and experimental data, were established for tin and lead. The simulation predictions are in good agreement with experimental results.

The Effects of Adding TiC Powders to VANADIS 4 Tool Steel by HIP Treatment

In this study, the commercial VANADIS 4 (V-4) tool steel powders with sifting classification below 25 μm to be the matrix with fine titanium carbide (TiC) powder to produce a new material with high hardness and wear resistance, via powder metallurgy, sintering and HIP (Hot Isostatic Pressing) process. Experimental results showed that the TRS of original V-4 steel powder was 678.5 MPa, but below 25 μm of V-4 steel powder adding 35 wt% TiC enhanced to 868.6 MPa through 1673 K sintered. Beside, the hardness increased to HRA 86.2, TRS reached 1059.3 MPa, and porosity decreased to 1.0% of the V-4 steel powders (below 25 μm) added 35 wt% TiC after 1673 K sintered and heat treatments. Furthermore, HIP treatment can improve the microstructure and mechanical properties of V-4 composite material. TRS of V-4 composite steel increased to 1180.4 MPa and hardness was HRA 87.4 (HRC 71.7), porosity decreased to 0.71% after 1673 K sintered and HIP (1523 K, 150 MPa, 1 hour) treatments.

Bulk amorphous Ni 59Zr 20Ti 16Sn 5 alloy fabricated by powder compaction

The possibility of fabrication of bulk amorphous Ni 59Zr 20Ti 16Sn 5 alloy by hot isostatic pressing of powders was investigated. The amorphous powders were obtained by ball milling of amorphous melt spun ribbon and by mechanical alloying of a mixture of powders of pure crystalline elements. Fully amorphous bulk samples were successfully obtained by hot isostatic pressing of both types of powders. However, at least 10% porosity of the sample fabricated from the ball milled ribbon was observed. Further optimisation of the compaction process needs to be performed.

Manufacture of a shield prototype for primary wall modules

In the frame of the blanket module (BM) development for ITER, an R&D programme was implemented for the manufacture of a shield prototype by powder hot isostatic pressing (HIPping). The manufactured shield is a full-scale module No. 11a. Starting from a forged block of 1350 mm × 1300 mm × 450 mm, the main machining steps as deep drilling (1200 mm), 3D machining and sawing were performed. Tubes were 3D bent and large number of small parts were designed and machined. By welding together all the sub-parts we erected the main part of the water coolant circuit. Once the water circuit was built; the shield was completed using powder HIPping together with forged block embedding the tubes in a final solid part. The powder/solid HIP is used to minimize the number of BM seal welds in front of plasma. It increases the reliability of the components during operation. About 300 kg of stainless steel powder was densified together with the forged block. 3D measurement was done before and after the HIP cycle to collect the data to be compared with theoretical model. It allows to predict the main distortions of the solid bulk. Ultrasonic examination of the densified powder on the stainless steel bulk and around the bended tubes was performed as well as mechanical characterization of the samples. The recess for stub key attachment on the vacuum vessel side, the hydraulic connector, the key for the primary wall panel attachment on the front side and the link between the four parallel water coolant circuits were then machined to achieve the shield prototype.

Testing of silicon nitride ceramic bearings for total hip arthroplasty

Modern ceramic bearings used in total hip arthroplasty (THA) consist of a femoral head (ball) articulating inside a hemispherical acetabular cup (socket); the ball and socket are made of alumina (Al(2)O(3)) and Al(2)O(3)-based composite materials. In the present study, total hip bearings were made from a different ceramic material, silicon nitride (Si(3)N(4)), by sintering and hot isostatic pressing of powders. The resulting material had improved mechanical properties over modern Al(2)O(3) THA bearings, with a flexural strength of 920 +/- 70 MPa, a Weibull modulus of 19, and a fracture toughness of 10 +/- 1 MPa m(1/2). Unlike zirconia-based ceramics that have also been used in THA, accelerated aging of Si(3)N(4) did not adversely affect the flexural strength. In simulated wear tests, Si(3)N(4) acetabular cups produced low-volumetric wear whether articulating against Si(3)N(4) or cobalt-chromium (CoCr) femoral heads. The results of this investigation suggest that Si(3)N(4) may allow improved THA bearings that combine the reliability of metal femoral heads with the low wear advantages of ceramic materials.

Hot isostatic pressing of powder in tube MgB2 wires

The critical current density (Jc) of hot isostatic pressed (HIPed) MgB2 wires, measured by dc transport and magnetization, is compared with that of similar wires annealed at ambient pressure. The HIPed wires have a higher Jc than the annealed wires, especially at high temperatures and magnetic fields, and higher irreversibility field (Hirr). The HIPed wires are promising for applications, with Jc>106 A/cm2 at 5 K and zero field and >104 A/cm2 at 1.5 T and 26.5 K, and Hirr∼17 T at 4 K. The improvement is attributed to a high density of structural defects, which are the likely source of vortex pinning. These defects, observed by transmission electron microscopy, include small angle twisting, tilting, and bending boundaries, resulting in the formation of subgrains within MgB2 crystallites.

Rheology of calcite–quartz aggregates deformed to large strain in torsion

High‐temperature, high‐pressure torsion experiments have been conducted on Solnhofen limestone and synthetic calcite–quartz aggregates to investigate the evolution of mechanical strength and microstructure to large strains. Hot isostatic pressing of powders containing 1–30 wt% quartz particles produced synthetic two‐phase aggregates containing trace amounts of wollastonite. The experiments were performed at constant twist rate, 300 MPa confining pressure, and temperatures ranging from 900 to 1300 K in the stability fields of calcite plus quartz and wollastonite plus carbon dioxide. The mechanical data from torsion tests of most samples show a pronounced peak stress at shear strains <1 and subsequent weakening. For most samples, a steady state stress is reached only at shear strains >5. A distinct shape and lattice preferred orientation developed in Solnhofen limestone and in the calcite matrix of the synthetic aggregates. However, at large shear strains, flattened porphyroclasts were almost entirely consumed by recrystallization. Elongation parallel to the specimen axis at temperature below 1100 K is possibly due to rotation of minerals into a preferred crystallographic orientation. Stress exponent and activation energy for creep of the calcite–quartz aggregates increase substantially with increasing quartz content. The strength of the two‐phase aggregates increases with quartz fraction up to 20 wt% by a factor of 2–5 depending on temperature and finite strain. Continuum models underestimate particle strengthening of the calcite–quartz aggregates. An alternative microphysical mechanism for the observed strengthening may be related to the reduced mobility of dislocations through diffusion of silicon into dislocation cores.

Manufacture of an ITER primary wall module shield prototype by powder hipping

The Shield Prototype manufactured by the European Home Team is representative of the Primary Wall Module No. 11 as designed for the ITER 1998 Design. This module was selected because it had the most complicated shape to fabricate due in particular to its double curvature in poloidal and toroidal directions. It consists of a stainless steel Shield block of about 4 tons, equipped with eight penetration holes through it and with all the features at the rear and side walls required for the module attachment system. All these requirements led to a complex cooling channel arrangement inside the module, making the fabrication by powder Hot Isostatic Pressing (HIPping) very attractive and competitive. This paper describes the main steps of the Shield Prototype manufacture and the results of the non-destructive examination. These results, which shall be confirmed by destructive examination, have shown so far the manufacturing feasibility by powder HIPping of the Shield of ITER Primary Wall Modules.

Manufacturing routes for stainless steel first wall panels

Hot isostatic pressing (HIP) techniques are being considered in the European Home Team as one of the fabrication routes to produce ITER-FEAT primary first wall panels (PFWP). To demonstrate the potential and the availability of such techniques, material development, innovative mock-up fabrications and numerical modeling for the production of near-net shape components are currently been studied by CEA/CEREM in collaboration with the EFDA-CSU Garching. The aim of this work is to investigate the manufacturing feasibility of advanced PFWP concepts, with reduced pitch between FW cooling channels and reduced material thickness between the FW cooling channels and the front surface, in order to improve the thermal fatigue performance of these concepts. In order to select the best fabrication route, two different manufacturing methods based on the HIP process are being considered. The first one consists in manufacturing of the first wall panel by a HIP forming technique. Mock-ups are made of a serpentine tube expanded into a proper matrix. 2-D computer modeling has been performed to estimate the serpentine deformation. The second manufacturing route is based on the powder HIP technique. Mock-ups have been made of a serpentine embedded into SS powder. In both cases, the objective was to obtain the minimum pitch between the stainless steel (SS) tubes and between the SS tubes and the front face.

Progress and critical issues of reduced activation ferritic/martensitic steel development

The inherent properties of reduced activation ferritic/martensitic (RAFM) steels include reduced swelling and high recycling potential, which make them likely candidates for application in commercial fusion power plants. The International Energy Agency (IEA) agreement has been an effective framework for international co-operation in developing RAFM steels. The progress and critical issues observed in this co-operation are reported. The production of RAFM steels on an industrial scale has been demonstrated. Various methods of fusion welding and solid hot isostatic pressing (HIP) are feasible for joining the steels. Manufacturing of complex shapes with the powder HIP method works well for RAFM steels. Major critical issues addressed concern the effects of simultaneous introduction of helium and displacement damage. The availability of a 14 MeV neutron source is identified as an essential tool to determine this effect. Finally, the potential of oxide dispersion strengthening to increase the operating temperature of RAFM steels is considered as an issue that has to be resolved to enlarge the application temperature window of RAFM steels.

Evaluation of mock-ups before manufacture of a shield block prototype by powder HIP

Hot isostatic pressing (HIP) of powder is proposed as a possible process for manufacturing primary wall blanket modules for the International Thermonuclear Experimental Reactor (ITER). The method is cost-effective and offers very good design flexibility. It also provides required, uniform material properties, and the material is easy to check with ultrasonic techniques. Bodycote Powdermet conducted a development programme as a part of a NET (Next European Torus) contract to manufacture a shield block for the ITER primary wall module prototype. The aim was to test the influence of geometry of the tube gallery on the tolerances of tube positions after HIP of one-eighth scale (724×318×299 mm 3) prototype mock-ups. It also intended to verify results obtained earlier on the influence of fabrication parameters. Five mock-ups were produced. Four HIP cycles were tested using two different designs of the cooling galleries. Non-destructive testing was used and measurements on sections of the mock-ups were performed. The location of tubes facing the first wall is most important. Investigation showed very small differences between the locations of those tubes in the five mock-ups. For these mock-ups, the tolerances between the surface and the tubes could be kept within ±2 mm.

Engineering design of the ITER blanket and relevant research and development results

The design of the ITER blanket is presented together with the related technology which has been developed. The evolution of this component since the beginning of the EDA is explained in relation to the developing understanding of the thermal deformations and of the electromagnetic forces. These loads lead to a system composed of compact modules protecting a continuous support shell called a backplate. The backplate is a stiff double wall construction which conveys the coolant to the modules. The supports of the module are flexible and allow relative thermal expansions. They are connected and disconnected to the backplate by bolts operated through holes in the front face of the module. The coolant connections and the electrical straps located on the back of the modules are reached similarly. The first wall is integral with the module and cooled in series. A research and development program on materials and joining methods defined the construction path which has been tested in prototypes. The main body is built of stainless steel by forging and drilling or powder hot isostatic pressing (HIP), depending on the complexity of the shape. The first wall includes a dispersion strengthened copper heat sink which is hot isostatic pressed onto the steel body. Beryllium is the basic plasma facing material and is attached by HIP to the copper. Prototypes of the module attachment have been built and are under integrated tests.

Structural materials by powder HIP for fusion reactors

Tokamak blankets have complex shapes and geometries with double curvature and embedded cooling channels. Usual manufacturing techniques such as forging, bending and welding generate very complex fabrication routes. Hot Isostatic Pressing (HIP) is a versatile and flexible fabrication technique that has a broad range of commercial applications. Powder HIP appears to be one of the most suitable techniques for the manufacturing of such complex shape components as fusion reactor modules. During the HIP cycle, consolidation of the powder is made and porosity in the material disappears. This involves a variation of 30% in volume of the component. These deformations are not isotropic due to temperature gradients in the part and the stiffness of the canister. This paper discusses the following points: (i) Availability of manufacturing process by powder HIP of 316LN stainless steel (ITER modules) and F82H martensitic steel (ITER Test Module and DEMO blanket) with properties equivalent to the forged one. (ii) Availability of powerful modelling techniques to simulate the densification of powder during the HIP cycle, and to control the deformation of components during consolidation by improving the canister design. (iii) Material data base needed for simulation of the HIP process, and the optimisation of canister geometry. (iv) Irradiation behaviour on powder HIP materials from preliminary results.

Superplastic Foaming of Titanium and Ti-6Al-4V

ABSTRACTSolid-state foaming of metals can be achieved by hot-isostatic pressing of powders in presence of argon followed by expansion of the resulting high-pressure argon bubbles at ambient pressure and elevated temperature. This foaming technique was first demonstrated by Kearns et al. [1] for Ti-6Al-4V, but is limited by its low creep rate and ductility, which lead to early cell wall fracture. We address these issues by performing the foaming step under superplastic conditions. Rather than using microstructural superplasticity (requiring fine grains which are difficult to achieve in porous powder-metallurgy materials), we used transformation superplasticity, which occurs at all grain sizes by biasing with a deviatoric stress (from the pore pressure) of internal stresses (from the allotropic mismatch during thermal cycling about the allotropic temperature range). As compared to control experiments performed under isothermal creep conditions, superplastic foaming under temperature cycling of unalloyed titanium and alloyed Ti-6Al-4V led to a significantly higher pore volume fraction and higher foaming rate.

Use of tungsten coating on iter plasma facing components

As part of the US ITER research and development activities, approaches to applying tungsten clads to copper, along with the development of a transpiration-cooled tungsten for use as a disruption energy dump, are being investigated. Joining is being attempted by diffusion bonding using nickel or titanium interlayers. Reduction in bondline residual stresses is being accomplished by use of functionally graded layers of tungsten and copper with copper as the continuous phase. Layers are being fabricated using vacuum plasma spray, liquid phase sintering and powder hot isostatic pressing. Initial metallographic results are promising, with fabrication of tensile and high heat flux specimens planned. Direct infiltration of 74% dense tungsten with magnesium and lithium is planned.

The effect of rare-earth filling on the lattice thermal conductivity of skutterudites

Polycrystalline samples of Ir4LaGe3Sb9, Ir4NdGe3Sb9, and Ir4SmGe3Sb9 have been made by hot isostatic pressing of powders. The lattice thermal conductivity of these filled skutterudites is markedly smaller than that of IrSb3; thus, void filling shows promise as a method for improving the thermoelectric properties of these materials. We present the lattice thermal conductivity of these filled skutterudites in an effort to quantify the impact of void filling in this structure. It is believed that the atoms ‘‘rattle’’ in the voids of the structure and therefore interact with a broad spectrum of lattice phonons, reducing their mean free paths substantially below that in the ‘‘unfilled’’ skutterudites. An additional phonon scattering mechanism is caused by phonon-stimulated transitions between the low-lying energy levels of the 4f electron configurations in the case of Nd3+ and Sm3+. Magnetic susceptibility and Hall-effect measurements are also presented.

A micro mechanical based constitutive model for finite element simulation of hot isostatic pressing of powder

Hot isostatic pressing (HIP) facilitates new designs and product shaping, for example by direct manufacture of composite products with differing materials in the various parts (compound). The specific material characteristics are thus created at the manufacturing stage (consolidation), and these in themselves often give good possibilities regarding shape, so-called NS (Net Shape)—or NNS (Near Net Shape)—manufacture. The HIP-technique is used economically in the low series production of complex-shaped steel parts. In order to achieve quality products, an integration of material, design and manufacturing technology is necessary, since the function and cost of the final component depends to a large extent on the development of production technology and its integration with design technology. Simulation of the hot isostatic pressing process is required to reduce the need for expensive and time-consuming experimental design. The use of finite element techniques in analyses of the highly non-linear process is preferable, especially for complex-shaped components. In this work, a micro-mechanical based continuum mechanics model for finite element analysis is presented. The model is used in the finite element simulation of hot isostatic pressing of two components. The results from the analyses correspond well with the experimental results.

High density processing of high performance ferrous materials : H.G. Rutz, F.G. Hanejko. (Hoeganaes Corporation, Riverton, New Jersey, USA), Int. J. Powder Metallurgy, vol 31, no 1, 1995, 9–17

Porous biomedical implants are known for their improved osseointegration due to the ingrowth of bone tissues, combined with a lower elastic modulus to solid implants, resulting in a reduced likelihood for stress shielding and implant loosening. In this work, the control of the porosity content in capsule-free powder hot isostatic pressing (CF-HIPing) of 316L stainless steel was investigated. The proposed approach utilises cold isostatic pressing (CIPing) to form green compacts using rubber moulds, followed by CF-HIPing under suitable conditions. Porosity control was attained via the selection of the powder particle size used in creating the green compacts. The microstructural and mechanical properties development of the CF-HIPed structures was studied using optical and scanning electron microscopy, micro-computer tomography, hardness, and compression testing. The occurrence of powder necking was visualised using electron backscattered diffraction. The results showed a significant increase in the pore fraction of the samples by increasing the particle size of the powder. However, increasing the particle size was also associated with a drop in the elastic modulus, compressive strength, ductility, and hardness of the final structures. Nonetheless, porous structures with elastic modulus between 17 and 30 GPa were successfully produced using a powder particle size range of 32–50 μm, matching the elastic modulus of human bones.

Some properties of semiconducting IrSb3

Polycrystalline p-type samples of IrSb3 and Ir0.5Rh0.5Sb3 have been made by hot isostatic pressing of powders. A number of properties such as thermal expansion coefficient, sound velocity, thermal conductivity, electrical conductivity, Seebeck coefficient, and carrier concentration have been measured. These compounds show promise as thermoelectric materials.