If advanced manufacturing technologies are to be adopted over conventional manufacturing processes in the nuclear industry — the most regulatory challenging industry — rigorous fundamental studies that develop underpinning knowledge, materials performance data, and predictive capabilities are essential. Herein we have employed the use of electron backscatter diffraction (EBSD) and 3D X-ray computed tomography (XCT) to characterize microstructure evolution and porosity consolidation during the early stages of powder metallurgy hot isostatic pressing (PM-HIP). The data herein highlight the mechanisms through which the powder particle size distribution encourages localized plastic deformation and subsequent microstructural recrystallization of Type 316L stainless steel; the effect of powder particle size distribution on the rate of porosity consolidation is also discussed. Specifically, we have determined the temperature and pressure conditions that are required to initiate dynamic recrystallization during HIP, and explain how this is influenced by the powder particle size distribution.

Kevlar composite materials are getting scientific interest in repairing of oil and gas pipelines in both offshore and onshore due to their unique properties. Curing is one of the major factor in deciding the final mechanical performance of laminated Kevlar/epoxy nanocomposites. The parameters such as curing time, temperature and applied pressure during the hot pressing will affect chemistry of crosslinking of the epoxy matrix and interaction of epoxy with the Kevlar fiber. The present study is carried out to evaluate the optimal curing conditions of the Kevlar/epoxy nanocomposites. Three different nanofillers (namely Multi walled Carbon nanotubes (MWCNT), Silicon Carbide (SiC) and Aluminum Oxide (Al 2 O 3 )) are incorporated in different weight percentage. Differential Scanning Calorimetry (DSC) and Thermo-Gravimetric Analysis (TGA) tests are carried out to determine the thermal stability and optimal curing conditions. Mechanical performance is investigated by conducting flexure, and drop weight tests. The results show that, the optimal curing temperature for maximizing the mechanical properties is at 170°C. Peeling off the Kevlar layers are observed for nanocomposite samples cured under 100°C. Mechanical strength of the composites is enhanced by optimizing the curing conditions and nanofiller contents.

Hot Isostatic Pressing (HIP) of type 316L austenitic stainless steel powder has been an established manufacturing practice for more than twenty five years within the oil and gas sectors and more recently in the naval defence industry. The successful ASME Code Case approval (N-834) has facilitated the manufacture of 316L components via Powder Metallurgy HIP (PM/HIP) for the civil nuclear sector. However, a number of issues have tended to hinder the uptake of PM/HIP as an alternative viable manufacturing route for both castings and forgings. Firstly, the powder specification for 316L and HIP processing parameters has typically been left to the discretion of the manufacturers. As such, the finer details of HIP product specification require greater clarity and definition for optimum performance/reproducibility. Secondly, comparison of historical data for 316L PM/HIP has shown variation in the Charpy impact toughness performance. These differences have been attributed to the oxygen content of the atomised powder, with greater oxygen contents yielding product with reduced impact properties. Based on these factors, a systematic study of the current state of the art of 316L commercial powder production, encapsulation/consolidation and selected HIP parameters was undertaken in collaboration with the Electric Power Research Institute (EPRI). A 316L powder specification was developed that primarily limited the oxygen content of the powder to under 130ppm. This lower oxygen limit reflects the improvements that commercial powder suppliers have been making over the past decade to ensure greater powder cleanliness. The test programme generated a significant body of test data based on 3 × 3 × 3 matrix of: powder supply, HIP service provider and HIP sustain times. The results were excellent across the full range of variables studied with all test billets passing the specification requirements of ASTM A988 and additional imposed requirements. Very consistent 316L material properties were produced for billets manufactured via differing HIP service providers across the comprehensive destructive test programme. This demonstrates the robustness and uniformity of the PM/HIP supply chain in producing 316L material of the requisite quality. In addition, no significant difference in material properties was noted for material pressed between 2–8 hours hold time, suggesting that the HIP process window is large with respect to hold time. Of significant note was that material produced with one powder yielded material with consistently the highest strengths and Charpy impact toughness. This has been attributed to chemical composition of the powder, which featured both a low oxygen and also a high nitrogen content.

We have recently reported on the mechanistic differences in ductile failure between stainless steel manufactured by hot isostatic pressing (HIP) and forging, from which it was established that the oxygen concentration must be properly controlled. As part of an ongoing investigation into the mechanics of ductile failure in novel HIP materials, X-ray CT has been employed as a tool to quantify and characterize the differences in ductile damage below the fracture surface of failed compact tension fracture toughness test specimens. Herein we report on some of the challenges associated with handling data relative to the fracture surface, which can extend far into the cores under investigation.

Dissimilar metal nozzle-to-safe end welds represent a complex manufacturing operation for nuclear reactor fabrication. Transitioning from a low alloy steel nozzle to corrosion-resistant reactor coolant system piping systems requires weld buttering, an intermediate heat treatment, and a dissimilar metal weld between the nozzle buttering and safe-end. The process can be both time consuming and costly, and often provides difficulties for inspection of welds in the field. Through the use of powder metallurgy and hot isostatic pressing (PM-HIP), a series of transition joint configurations have been evaluated that could reduce the complexity of nozzle-to-safe end fabrication by eliminating fusion welding from the process. Test coupons of SA508 low alloy steel have been joined via PM-HIP to either 316L SS or 347NG SS using various powder metal interlayer materials (Alloy 82, Nb-modified Alloy 600 (600M), Alloy 690, and 316L SS). The microstructural evolution and mechanical performance of the joints have been evaluated following a post-HIP solution anneal, quench and temper heat treatment. Particular attention was given to evaluating bond-line regions via Charpy V-notch impact testing, tensile testing, microhardness, optical microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Results demonstrate that multiple transition layer configurations are capable of meeting the acceptable tensile and impact energy specifications of the two parent base material substrates. Interface impact toughness and ductility were dependent upon secondary phase precipitation within the diffusion region of the joints and presence of non-metallic inclusions. This assessment demonstrates that acceptable joint performance is achievable through proper material selection and should be considered for DMW applications in the future.

Based on the good experiences gained by using small specimens made of ferritic RPV materials, the Master Curve fracture toughness approach was applied to determine the fracture mechanical properties of oxide dispersion strengthened (ODS-) materials. A ferritic ODS-alloy (Fe-14Cr-1W-Ti-Y 2 O 3 ) has been produced through the powder metallurgical production path via hot extrusion and hot isostatic pressing (HIP). Optimized oxide dispersion strengthened (ODS)-alloys have a promising potential to meet the foreseen requirements of components in future Gen IV power plants due to their high creep strength and swelling resistance under irradiation at elevated operational temperatures. The fracture toughness was characterized with mini 0.2T C(T) specimens in different material orientations (R-L / L-R) in the ductile-brittle and upper shelf region in the un-irradiated state, accounting especially for the ODS-material’s anisotropy as one key effect of manufacturing. Despite all tests were performed in orientation required by ASTM standards E 1921 and E 1820 not all validity criteria (e.g. height of yield strength, evenness of the crack, admissible K during testing or admissible stable crack growth) were met by the ODS-material: consequently, a valid T 0 value and a standard-compliant Master Curve could not be determined for the ODS-material in the transition region especially in the respective R-L orientation, also due to a comparably low fracture toughness over the whole evaluated temperature range. Promising fracture toughness properties were obtained in the crack growth direction perpendicular to the prior main deformation (extrusion) direction, where a K JQ value of 196 MPa√m at T = 22°C was measured. Within the ductile regime, only a J Q = J 0.2BL technical initiation toughness value could be calculated and at T = 22°C, a comparably large J Q of 137kJ/m 2 is obtained for specimens with crack growth direction perpendicular to the extrusion direction, while in extrusion direction the toughness is again low. In addition two further ODS-materials (14YWT and PM2000) were tested and compared to the alloys above. Non-conformances of ODS relating to the material requirements in ASTM standards E1921 and E1820 were finally detected and explained.

With near-net shape technology becoming an increasingly desirable route toward component manufacture due to its ability to create components with increasingly complex geometries, minimizing the number of potential welded joints, as well as reducing machining time and associated costs, it is important to demonstrate that components fabricated via Hot Isostatic Pressing (HIP) are able to perform to similar standards as those set by equivalent forged materials. Hot Isostatically Pressed (HIP’d) materials are typically accredited with displaying enhanced yield strengths, ultimate tensile strengths, and ductility over their forged counterparts. In this paper we explore the effects of oxygen, which resides in the austenite matrix during the HIP manufacture process, on a material’s fracture toughness properties. We quantify the influence of different concentrations of oxygen on both the microstructural and mechanical properties of HIP’d 304L and 316L stainless steel, highlighting the benefit of reducing the oxygen as much as possible. Various mechanical tests have been performed on materials containing a range of oxygen contents (between 100 ppm and 200 ppm) and over a large temperature range, including J 1C fracture toughness testing, instrumented Charpy, and tensile, and the mechanistic involvement of residual oxygen on the results is discussed. The effects of oxygen become more apparent at cryogenic temperatures, whereas the fracture behavior of HIP’d and forged variants of 304L and 316L at elevated temperatures appears to be comparable.

It is well known throughout the PM HIP (Powder Metallurgy Hot Isostatic Pressing) industry that PM HIPed 316L material in general exhibit higher strength than conventional 316L. However, previous studies have shown an uncharacteristic behavior in impact toughness properties at cryogenic temperatures compared to conventional forged material. The uncharacteristic behavior consists of unexpectedly large drop in impact toughness at cryogenic temperatures which is not seen in the same extent in conventional material e.g. forged 316L. With the recent code case approval for PM HIPed 316L material, this behavior can be seen as an uncertainty regarding the performance of the material and its use in nuclear applications can therefore become limited. The behavior and underlying mechanisms is yet to be explained in detail. One possible explanation is that it is caused by oxides in the material, of which a large amount originates from oxygen picked up by the very large surface area of the powder during the manufacturing process. The correlation between impact toughness at room temperature and oxygen content is often referred to. In this study the non-metallic inclusion content is correlated to the impact properties at −196°C (−321°F), and a suggested explanation for the behavior of PM HIP 316L/316LN vs. conventional 316L is presented. The size and number of inclusions constitutes a major difference between the PM HIPed and conventional material. The results show that the size of the inclusions is significantly smaller in the PM materials compared to the conventional material and as a consequence they are present in larger numbers in the PM materials. Furthermore, the results clearly show the correlation between inclusion content and the impact toughness at cryogenic temperatures. The correlation is not as clear at room temperature where the different materials behave more similar. The suggested explanation is further supported by literature on cryogenic properties of 316L/316LN, 316L weld material and PM HIP 316LN with greatly reduced oxygen content. The impact toughness testing was performed using instrumented test equipment capable of recording load vs. displacement during testing. From this data the crack propagation and crack initiation energy can be estimated. Furthermore, it is known that grain size can influence mechanical properties. In this study no clear relationship between impact toughness and grain size could be observed. However, a correlation between the grain size and the amount of inclusions in the material was observed. It was found that larger amounts of inclusions in the PM HIPed material are correlated to a finer grain size. The results indicate that the inclusion particles inhibit grain growth during the HIP and heat treatment process by pinning of grain boundaries.

Because “safety” is still the key point in the Nuclear industry, more than in any others, the use of new materials or new manufacturing methods is really challenging. Among many characterizations required for a new steel grade or a new manufacturing process to be accepted and then introduced in a Nuclear design code, the fatigue properties must be determined with great care. Nowadays, the consideration of the Pressurized Water Reactor (PWR) primary water environment effect on the Low Cycle Fatigue (LCF) behavior of Austenitic Stainless Steels (ASS’s) is an important issue for both Nuclear Power Plants (NPP) lifetime extensions and new builds as described in the NUREG/CR-6909 [1], [2]. This paper aims to present the LCF behaviors in air and in PWR water at 300°C of type 304L and 316L ASS’s manufactured by Powder Metallurgy coupled with Hot Isostatic Pressing process (PM/HIP) and to compare them with those observed on usual ASS nuclear grade products [3]-[6]. As already introduced in our previous paper [7] dedicated only to the PM/HIP 304L steel fatigue behavior, it appears that the microstructures, mechanical properties and LCF behaviors in air and in PWR water of both type 304L and 316L steels manufactured by PM/HIP process are better or at least similar to those observed on wrought ASS’s.

In most industries and more particularly in the Nuclear one, the use of new materials or new manufacturing methods is really challenging because “safety” is still the key point. Among many characterizations required for a new steel grade or a new manufacturing process to be accepted and then introduced in a Nuclear design code, the fatigue properties must be determined with great care. Nowadays, the consideration of the Pressurized Water Reactor (PWR) primary water environment effect on the Low Cycle Fatigue (LCF) behavior of Austenitic Stainless Steels is an important issue for both Nuclear Power Plants (NPP) lifetime extensions and new builds as described in NUREG/CR-6909 [1]. This study aims to present the LCF behavior in Air and in PWR water at 300°C of a type 304L steel manufactured by Powder Metallurgy coupled with Hot Isostatic Pressing process (PM/HIP) and to compare them with those observed on 304L nuclear grade products such as rolled plate or forged branch [2–5]. It appears that the LCF behavior in Air and in PWR water of this 304L HIP material is better or at least similar to the one observed on classical 304L steels.

This paper presents an overview of the work undertaken by Rolls-Royce to justify the use of a Hot Isostatically Pressed (HIP) Reactor Circulating Pump (RCP) bowl manufactured in 316L stainless steel for a Pressurised Water Reactor (PWR) application. It presents the work from a design justification/manufacturing quality assurance perspective, rather than from a pure metallurgical perspective. Although the HIP process is not new, it was new in its application to Rolls-Royce designed nuclear reactor plant. As a consequence, Rolls-Royce has implemented an evolving, staged approach, starting with HIP bonding of solid valve seats into small bore valve pressure boundaries. This was followed by powder HIP consolidation of leak-limited, thin-walled toroids, and has culminated in the powder HIP consolidation of thick-walled components such as RCP bowls. The paper provides an overview of each of these stages, the method of manufacture for the RCP bowl, and the approach taken with respect to justification. In previous Rolls-Royce applications of HIP to PWR plant components, the component section thickness has been fairly consistent. For the RCP bowl application, the section thickness varies quite considerably. To assess any variation in properties as a result of section thickness variation, a stepped wedge technology demonstrator was first manufactured and non-destructively and destructively examined to assess whether material properties remain within specification. The paper presents material property results for ‘Near Surface’ and ‘Buried’ samples taken from section thicknesses covering 50mm to 300mm. Yield, Ultimate Tensile Strength (UTS), Charpy ‘V’ notch impact strength and Strauss test results were found to be within specification for all section thicknesses. An analysis of the data shows no statistical difference in material properties across the different section thicknesses for both near surface and buried properties, except for Charpy ‘V’ notch impact strength, for which, above 50mm, mean ‘Buried’ strength is significantly higher than mean strength for ‘Near Surface’. It is observed that the mean ‘Near Surface’ yield and tensile strength appears to increase with section thickness; however, there are insufficient data to demonstrate whether or not the increase is statistically significant. There appears to be a reduction in mean ‘Buried’ yield strength when the section thickness is at 300mm, compared to thinner sections, but again, the current data are insufficient to determine whether or not the reduction is statistically significant. It could be postulated that there is a point at which the section thickness starts to influence the cooling rate, and as a consequence grain growth may be more prominent at the ‘Buried’ position. This could result in yield and tensile material properties being detrimentally affected. However, this is not supported by an analysis of Charpy ‘V’ notch impact strength results, for which a similar reduction would be expected; the highest ‘Buried’ Charpy results occur in the thickest section. Further work is ongoing to understand this observation. Non-destructive examination results of a prototype RCP bowl are presented. This shows no defects identified from dye penetrant surface examination and ultrasonic testing for a rejection level set at a 3mm flat bottomed hole.

Hot Isostatic Pressing (HIP) of gas atomized powder has its major application for superalloys and high alloyed steels as e.g. tool steels, high speed steels and stainless steel. The HIP route offers not only finer microstructure and thus better mechanical properties in these alloys but also the possibility to make near net shape end products with isotropic properties. The expansion of the PM HIP Technology towards lower alloyed steels has been considered uneconomical compared to conventionally produced parts and sometimes not even feasible from a technical point of view. The major drawback has been the often reported inferior impact energy. This technical report will address how various parameters in the PM HIP process will influence the mechanical properties of end products and particularly causes and possible solutions to the impact problem.

Hot pressing process is widely used in automotive, shipbuilding, energy production and civil engineering. However, the trial and error technique that is intensive time and energy consuming is still used. Particularly, the design of Francis turbines of hydropower plants is not standard, but variable from site to site due to hydraulic conditions and cost of energy. As a result, the blade hydraulic profile of each Francis turbine is different. The blades, one of the key components of Francis turbine runners, are produced in small batches and the setup of the dedicated punch and die increases significantly the unit production costs. In this paper, the blade unfolding process for optimal blank design will be firstly presented, and then a hot pressing process for very thick plates is proposed. The pressing process of high strength steel at hot temperature is characterized by thermo-mechanical behaviors, three-dimensional unsteady deformation, high nonlinearity, continuous local forming. The analyses of residual stress distribution and applied forces are carried out.

The Calcine Disposition Project (CDP) of the Idaho Cleanup Project (ICP) has the responsibility to retrieve, treat, and dispose of the calcine stored at the Idaho Nuclear Technology and Engineering Center (INTEC) located at the Idaho National Laboratory. Calcine is the granular product of thermally treating, or calcining liquid high-level waste (HLW) that was produced at INTEC during the reprocessing of spent nuclear fuel (SNF) to recover uranium. The CDP is currently designing the Hot Isostatic Pressure (HIP) treatment for the calcine to provide monolithic, glass-ceramic waste form suitable for transport and disposition outside of Idaho by 2035 in compliance with the Idaho Settlement Agreement. The HIP process has been used by industry since its invention, by Battelle Institute, in 1955. Hot isostatic pressing can be used for upgrading castings, densifying pre-sintered components, and consolidate powders. It involves the simultaneous application of a high pressure and temperature in a specially constructed vessel. The pressure is applied on all sides with a gas (usually inert) and, so, is isostatic. The CDP will use this treatment process (10,000 psi at 1,150 C) to combine physically and chemically a mixture of calcine and granular additives into a non leachable waste-form. The HIP process for calcine involves filling a metal can with calcine and additives, heating and evacuating the can to remove volatiles, sealing the can under vacuum, and placing the can within the HIP machine for treatment. Although the HIP process has been in use for over 50 years it has not been applied in large scale radioactive service. Challenges with retrofitting such a system for Calcine treatment include 1) filling and sealing the HIP can cleanly and remotely, 2) remotely loading and unloading the HIP machine, and 3) performing maintenance and repair on a 300 ton, hydraulically actuated machine in a highly radioactive hot cell environment. In this article, a systems engineering approach, including use of industry-proven design-for-quality tools and quantitative assessment techniques is summarized. Discussions on how these techniques were used to improve high-consequence risk management and more effectively apply failure mode, RAMI, and time and motion analyses at the earliest possible stages of design are provided.

Hot Isostatic Pressing (HIP) has been used for many years to consolidate porosity in cast metal shapes to improve mechanical properties. When applied to fine metal powders, it is possible to produce Near Net Shape (NNS) items and more complex geometry components that are fully dense and offer an attractive set of properties at reduced cost. NNS items from powder deliver cost savings by reducing initial material usage and subsequent machining costs. Powder production and HIP processing are automated methods, which provide protection against forging route obsolescence. Setup costs are lower and batch sizes smaller, particularly well suited to small numbers of high integrity components. HIPped powder microstructures are isotropic and equiaxed, with uniformly fine grain sizes not normally achieved in heavy section components, which facilitates ultrasonic NDE examination. Improved features to facilitate NDE are readily incorporated into the HIP assembly. Inclusion contents are lower and of more benign geometry, easing fracture assessment. Use of the technology has grown, particularly in the off-shore oil industry where it is already established in high integrity applications, particularly in place of welded joints. Take-up in the more conservative nuclear industry has been slow. The quality of HIPped powder items can provide through life cost savings since there is greater assurance of structural integrity compared to welded or wrought components. This paper presents a materials perspective on the way in which Rolls-Royce has gained experience with HIPped powders since the 1990s, initially with hardfacing materials to minimise welding defects and provide a robust manufacturing route. Building on this database, we have now established that HIPped powder 316L/304L components, in items up to several tons in weight, have equivalent or slightly better strength, toughness and corrosion resistance to their forged or cast counterparts. This data is now part of a submission to ASME for inclusion in the Pressure Vessel Code. Rolls-Royce now has a robust methodology in place to develop safety cases and is extending the number of applications in pressure boundary components on current and future classes of equipment. A strength-in-depth argument has been endorsed by external approval organisations and is supporting current submarine build programmes. Other applications in the growing civil nuclear market are now under consideration.

Hot Isostatic Pressing (HIP) has been used for many years to consolidate porosity in cast metal shapes to improve mechanical properties. When applied to fine metal powders, it is possible to produce Near Net Shape (NNS) items and more complex geometry components that are fully dense and offer an attractive set of properties at reduced cost. NNS items produced from HIPed powder deliver cost savings by reducing initial material usage and subsequent machining costs. Powder production and HIP processing are automated methods, which provide protection against forging route obsolescence. Setup costs are lower and batch sizes are smaller, which makes HIPping particularly well suited to small numbers of high integrity components. HIPed powder microstructures are isotropic and equiaxed, with uniformly fine grain sizes not normally achieved in heavy section components, which facilitates ultrasonic NDE examination. Improved features to facilitate NDE are readily incorporated into the HIP assembly. Inclusion contents are lower and of more benign geometry, easing fracture assessment. In a broad program of testing, Rolls-Royce has established (1) that HIPed powder 316L/304L components, in items up to several tons in weight, have equivalent or slightly better strength, toughness and corrosion resistance than the wrought equivalents. Rolls-Royce are extending their activities to HIPing of Inconel alloys. The first phase has been to HIP test samples of Inconel 600 and Inconel 690 alloys. Initial testing has produced promising results in line with expectations of wrought material. There has also been the opportunity to vary the HIPing cycle to assess the effect of processing parameters on the final product. An ability to HIP Inconel components is thought to be of benefit in new plant construction, where material is often not readily available in required thick section. The adaptability and good control of the HIP technique also shows promise as a manufacturing route for future high temperature materials which will be required in Generation 4 civil builds.

Put abstract text here. This paper summarizes manufacturing technologies of the water-cooled-solid-breeder (WCSB) blanket module for a fusion reactor using reduced activation ferritic/martensitic steel (RAFM). Although RAFM is very similar to commercial 9 Cr heat resistant steel, RAFM in the blanket is to be used as thin wall structure. Moreover, it is necessary to employ some new manufacturing technologies for the components such as hot-isostatic-pressing (HIP) and fiber-laser-welding (FLW). Some full-scale mock-ups of the blanket have been developed using conventional and newly developed method. The mock-ups have been developed in industrial scale, and the mock-ups demonstrated integrity in the service condition of the blanket without non-nuclear environment. The mock-ups demonstrated their soundness under the service condition of the blanket.

Hot Isostatic Pressing (HIP) has been used for many years to consolidate porosity in cast metal shapes to improve mechanical properties. When applied to fine metal powders, it is possible to produce Near Net Shape (NNS) items and more complex geometry components that are fully dense and offer an attractive set of properties at reduced cost. NNS items manufactured from powder deliver cost savings by reducing initial material usage and subsequent machining costs. Powder production and HIP processing are automated methods, which provide protection against forging route obsolescence. Setup costs are lower and batch sizes smaller, which makes the process particularly well suited to small numbers of high integrity components. HIPped powder microstructures are isotropic and equiaxed, with uniformly fine grain sizes not normally achieved in heavy section components, which facilitates ultrasonic NDE examination. Improved features to facilitate NDE are readily incorporated into the HIP assembly. Inclusion contents are lower and of more benign geometry, easing fracture assessment. Use of the technology has grown, particularly in the offshore oil industry where it is already established in high integrity applications, particularly in place of welded joints. Take-up in the more conservative nuclear industry has been slow. The quality of HIPped powder items can provide through life cost savings since there is greater assurance of structural integrity compared to welded or wrought components. In a broad programme of testing, Rolls-Royce has established that HIPped powder 316L/304L components, in items up to several tons in weight, have equivalent or slightly better strength, toughness and corrosion resistance than conventional forgings. Rolls-Royce now has a robust methodology in place to develop safety cases and is extending the number of applications in pressure boundary components on current and future classes of equipment. A strength-in-depth argument has been endorsed by external approval organisations and is supporting current submarine build programmes. Other applications in the growing civil nuclear market are now under consideration. A plan for developing an ASME Code Case for Powder HIP is being considered. This paper presents an update on the implementation process.

The fabrication of near net shape powder metal (PM) components by hot isostatic pressing (HIP) has been an important manufacturing technology for steel and stainless steel alloys since about 1985. The manufacturing process involves inert gas atomization of powder, 3D CAD capsule design, sheet metal capsule fabrication and densification by HIP in very large pressure vessels. Since 1985, several thousand tonnes of parts have been produced. The major applications are found in the oil and gas industry especially in offshore applications, the industrial power generation industry, and traditional engineering industries. Typically, the components replace castings, forgings and fabricated parts and are produced in high alloy grades such as martensitic steels, austenitic stainless steels, duplex (ferritic/austenitic) stainless steels and nickel based superalloys. The application of PM/HIP near net shapes to pump barrels for medium to high pressure use has a number of advantages compared to the traditional forging and welding approach. First, the need for machining of the components is reduced to a minimum and welding during final assembly is reduced substantially. Mechanical properties of the PM/HIP parts are isotropic and equal to the best forged properties in the flow direction. This derives from the fine microstructure using powder powder and the uniform structure from the HIP process. Furthermore, when using the PM HIP process the parts are produced near net shape with supports, nozzles and flanges integrated. This significantly reduces manufacturing lead-time and gives greater design flexibility which improves cost for the final component. The PM HIP near net shape route has received approval from ASTM, NACE and API for specific steel, stainless steel and nickel base alloys. This paper reviews the manufacturing sequence for PM near net shapes and discusses the details of several successful applications. The application of the PM/HIP process to high pressure pump barrels is highlighted.

Hot Isostatic Pressing (HIP) has been used since the 1980s to consolidate porosity in cast metal shapes and improve mechanical properties in conventional forgings and wrought components. The availability of high quality metal powders has made it possible to produce Near Net Shape (NNS) items and more complex geometry components that are fully dense and offer an attractive set of properties at reduced cost. Powder HIP manufacturing reduces initial material usage and subsequent machining costs. Metal powder production and HIP processing are automated methods, which also provide protection against forging route obsolescence. Setup costs are lower and batch sizes smaller. HIPped powder microstructures are isotropic and equiaxed, with fine grain sizes not normally achieved in heavy section components, which facilitates ultrasonic NDE examination. Inclusion contents are lower and of more benign geometry, easing fracture and safety case development. Although widely used in the off-shore oil industry in high integrity applications, particularly to reduce welded connections, in the nuclear industry interest has been limited. The quality of HIPped powder items can provide through life cost savings since there is greater assurance of structural integrity compared to welded or wrought components. In an extensive programme of testing, it was established that HIPped powder 316L and 304L components, in items up to several tons in weight, have equivalent or slightly better strength, toughness and corrosion resistance. HIPped powder items are now in service as pressure retaining components in PWR plant. Effort is now directed at widening the range of components for which the HIP process is appropriate focusing on reducing welds in the plant construction sequence. This is particularly relevant to pipework manufacture and assembly. The benefits of facilitating an ASME Code Case for Powder HIP are also being considered.