Hot Isostatic Pressing Process Research Articles

Improved structure and enhanced properties of detonation sprayed W coating via hot isostatic pressing

Tungsten has garnered significant attention for its superior performance as a plasma-facing material in tokamak devices. However, its hardness and high ductile-to-brittle transition temperature present challenges for its application in plasma-facing components. To address these issues, this study employs the detonation spraying (DS) technique to prepare tungsten coatings on a TZM alloy substrate and further optimizes their properties through hot isostatic pressing (HIP) treatment. Advanced characterization techniques were utilized to conduct a detailed microstructural and compositional analysis of the coatings. The results indicated that the HIP treatment significantly reduced the porosity of the coatings, improving their density and overall quality. Additionally, HIP treatment led to a decrease in internal stress, a reduction in dislocations, and the grain growth within the coatings. The study also discussed how the HIP process improved the microstructure of the DS tungsten coatings through these mechanisms, thereby enhancing the coatings' thermodynamic properties. Mechanical property tests revealed that the coatings treated with HIP exhibited higher bonding strength and lower hardness, attributed to the increase in grain size and the reduction in dislocation density within the coatings. Thermal property tests demonstrated that the HIP-treated coatings possessed higher thermal diffusivity and specific heat capacity in the temperature range of 100 to 500 °C. Furthermore, the performance of the coatings under transient high heat flux conditions was significantly improved after the HIP treatment, showing better resistance to the thermal shock and cracking. These findings are of great importance for understanding the performance enhancement of DS tungsten coatings in nuclear fusion reactor applications via HIP, especially as candidate materials for the first wall of tokamak devices.

Surface reactivity during a Hot Isostatic Pressing treatment of Ni-based superalloy René 77 specimens manufactured by Laser Powder Bed Fusion and Metal Inject Molding

Additive manufactured alloys are generally affected by porosity. To solve this issue, Hot Isostatic Pressing (HIP) is a mandatory step. This work focuses on the reactivity of Ni-based superalloy René77 during HIP at 1200 °C, in argon atmosphere. René77 is chromia-forming in air at this temperature, but during HIP treatment, it formed α-Al2O3, Al-Ti mixed oxides and TiX (X= nitrogen/oxygen/carbon). The relative quantities of these phases depend on the specimen position inside the furnace, suggesting a gradient of impurity partial pressures. By combining experiments with thermodynamic calculations, this work contributes to a better understanding of HIP processes and suggests ways of improving them.

Generation and propagation mechanism of cracks in welded joints of thin-walled capsules during hot isostatic pressing

The quality of the capsule has an important effect on the quality of hot isostatic pressing (HIP) products. The reliability of the capsule is a key factor in determining the success or failure of HIP. The capsule is mainly formed through a sheet welding process. In order to ensure the reliability of the weld in HIP, stainless steel with better high-temperature and high-pressure performance than Q235 steel needs to be used. In this case, the fusion line becomes a dissimilar-material interface, which is more prone to fusion-line failure. This paper focuses on examining and studying the formation mechanism of fusion line cracks in welded joints during HIP. The results show that, first, the increase of the HIP temperature weakens the strength near the fusion line significantly. Second, the higher the HIP temperature, the more severe the grain coarsening, and the grain size along the radial direction of the capsule exhibits a monotonic change. Third, since the HIP process changes the micro-zone grain orientation of mild steel, the distribution characteristics of ferrite and pearlite change as well. when the temperature and pressure are higher, the texture still exhibits a strong and complex distribution.

Ballistic performance of titanium-based layered composites made using blended elemental powder metallurgy and hot isostatic pressing

Metal matrix composites tiles based on Ti-6Al-4V (Ti64) alloy, reinforced with 10, 20, and 40 (vol.%) of either TiC or TiB particles were made using press-and-sinter blended elemental powder metallurgy (BEPM) and then bonded together into 3-layer laminated plates using hot isostatic pressing (HIP). The laminates were ballistically tested and demonstrated superior performance. The microstructure and properties of the laminates were analyzed to determine the effect of the BEPM and HIP processing on the ballistic properties of the layered plates. The effect of porosity in sintered composites on further diffusion bonding of the plates during HIP is analyzed to understand the bonding features at the interfaces between different adjacent layers in the laminate. Exceptional ballistic performance of fabricated structures was explained by a significant reduction in the residual porosity of the BEPM products by their additional processing using HIP, which provides an unprecedented increase in the hardness of the layered composites. It is argued that the combination of the used two technologies, BEPM and HIP is principally complimentary for the materials in question with the abilities to solve the essential problems of each used individually.

Structure and properties of samples made from XH50BMTJuB-VI (EP648-VI) alloy produced by using selective laser melting process

The paper presented examines the composition, the structure and properties of samples made from the XH50VMTJuB-VI (hereinafter EP648-VI) alloy obtained by using the selective laser melting process (the SLM-process) in relation to manufacturing parts for aviation purposes. The authors carried out a comparative study of the samples’ structure and properties upon conducting such operations as depositing in two directions (horizontal and vertical), separate heat treatment and after hot isostatic pressing (HIP) followed by a standard heat treatment process applied for deformable semi-finished products made from the XH50VMTJuB-VI(EP648-VI) alloy. The authors inform that the manufacturing of samples by means of the SLM-process involved powders obtained through the technology of the vacuum-induction spraying of the molten metal jet with an inert gas (argon). The paper has established that samples obtained by using the HIP process with the application of the heat treatment (a vacuum high-temperature homogenization followed by a long-term aging) demonstrated the best set of mechanical properties, since the implemented complex process ensured the “healing” of pores and discontinuities in the structure, and strengthening by means of the intermetallic g¢-phase, while separations of the excess, needle-shaped a -Cr phase are fine and evenly distributed in the material structure. The authors noted that mechanical properties of samples under analysis were generally in compliance with the requirements set forth in the regulatory documentation for deformable semi-finished products made from the XH50VMTJuB-VI (EP648-VI) alloy, while underlining the increase in the level of impact strength of samples that underwent the HIP process, and the long-term strength of samples manufactured in the vertical direction compared to other options studied. Following the results of the analysis, the authors established that the SLM-process made it possible to manufacture products whose level of mechanical properties was close to the level of the deformable material, and even exceeded it in some cases.

Matrix microstructure evolution during the fabrication of SiCf/Ti60 composites

Microstructure evolution during the hot isostatic pressing (HIP) of continuous silicon carbide fiber-reinforced Ti (SiCf/Ti) composites has not been investigated. In this study, SiCf/Ti60 composites were prepared via the HIP solidification method of Ti60 precursor wires. The evolution of the microstructure of the Ti60 precursor wires and SiCf/Ti60 composites was characterized using electron backscatter diffraction microscopy and transmission electron microscopy techniques. The results showed that the deformation of α-Ti was mainly accomplished by basal <a> dislocations and prismatic <a> dislocations slip during the HIP process. After the completion of HIP, the low-angle grain boundaries (LAGBs) were reduced to 24.6%, and the average grain size of α-Ti was increased to 7.47 μm2. Two fiber textures, <0001>//axial direction (AD) and <10-10>//AD strength, were present in α-Ti, with a 38% increase in <10-10>//AD strength. The phase contents of 1.0% β-Ti and 0.6% (Ti, Zr)6Si3 precipitated from different locations in the Ti60 matrix and induced changes in misorientation.

Comparison of the Microstructural, Mechanical and Corrosion Resistance Properties of Ti6Al4V Samples Manufactured by LENS and Subjected to Various Heat Treatments.

In this paper, the influences of two post-heat treatments on the structural, mechanical and corrosion resistance properties of additively manufactured Ti6Al4V alloys were discussed in detail. The materials were produced using the laser engineering net shaping (LENS) technique, and they were subjected to annealing without pressure and hot isostatic pressing (HIP) under a pressure of 300 MPa for 30 min at temperatures of 950 °C and 1050 °C. Annealing without pressure led to the formation of a thin plate structure, which was accompanied by decreasing mechanical properties and increasing elongation and corrosion resistance values. For the HIP process, the formation of a thick plate structure could be observed, resulting in the material exhibiting optimal mechanical properties and unusually high elongation. The best mechanical and corrosion resistance properties were obtained for the material subjected to HIP at 950 °C.

An investigation over microstructure and HIP processing effects on wear performance of pure chromium parts fabricated by laser powder bed fusion

Chromium (Cr) and its alloys have long been valued for their exceptional properties, including corrosion resistance and high-temperature stability, rendering them indispensable in industrial applications such as chemical processing, energy production, and aerospace. However, due to the difficulties in Cr-based alloy manufacturing, there is a need for novel manufacturing methodologies. Additive Manufacturing (AM) emerges as a promising approach, particularly Laser Powder Bed Fusion (LPBF), which allows for intricate designs, reduced material waste, and simplified assembly. However, certain issues still need to be addressed, including defects like cracks and porosities in the manufactured parts. Post-processing techniques such as Hot Isostatic Pressing (HIP) have gained prominence for enhancing the material properties and quality of AM parts, including those produced using LPBF. HIP treatments are effective in eliminating internal pores, although some challenges remain, notably the presence of trapped argon and grain coarsening side effects of HIP process parameters. This study focuses on LPBF-processed pure chromium parts with crystallographic texture and investigates their properties after HIP treatment, including microstructure, hardness, and tribological performance. According to the obtained results: the HIP process reduced cracks, especially in the center region, but increased gaps in the side region. HIP also hindered grain realignment, limiting grain growth, and resulting in high HAGB density and low MUD values. Elevated HIP processing pressure negatively affected tribological performance due to increased grain size, and reduced hardness. This study, for the first time, realized the effect of HIP conditions on the microstructure and tribological performance of LPBF-processed pure Cr.

In situ synthesis of titanium alloy powders reinforced with nanoparticles for powder bed fusion: A step towards safer and more sustainable manufacturing

Additive manufacturing technologies for metallic materials based on powder bed fusion, either with electron (PBF-EB/M) or laser beam (PBF-LB/M) have enormous industrial potential. It is known that the reinforcement of nanoparticles in the metallic matrix improves the mechanical properties. This study presents a novel method for manufacturing reinforced powder particles for PBF technology. The method involves dispersing and dissolving reinforcing nanoparticles in the metallic matrix, resulting in a composite material. The method was applied to a Ti‐6Al‐4V matrix with SiC nanoparticles as reinforcement to develop a new Titanium Matrix Composite (TMC). A route for atomizing the composite material has been developed to scale up the process on an industrial level. The atomized material has been designed to be used as feedstock with PBF-EB/M and PBF-LB/M. The feedstock is a composite powder obtained by the Electrode Inert Gas Atomization (EIGA) process after mixing and dispersing SiC nanoparticles in the Ti‐6Al‐4V matrix and consolidating the mixture into an ingot bar using Hot Isostatic Pressing (HIP). The powder bed fusion process parameters have been studied to obtain specimens with a density greater than 99.9%, and close to 100% after HIP process. The conditions for some heat treatments, such as HIP and stress relief, have been determined. The conditions of machining processes, such as milling and turning, have been studied. The material’s properties, such as chemical composition, microstructure, mechanical strength, and fatigue behavior have been evaluated. Compared to Ti‐6Al‐4V according to the ASTM F2924 standard, both the ultimate tensile strength and yield strength have been improved by 28%, and the elongation at break by between 30% and 60%. Regarding fatigue behavior, an increase of around 30–50% (high-low cycles) has been observed.

Investigation of the Formation of Structure and Properties in a Billet Made of Heat-Resistant Nickel Alloy EP741NP, Obtained by Hot Isostatic Pressing Technology

It is known that the technology of hot isostatic pressing (HIP) can reduce the residual porosity and increase the level of physical and mechanical characteristics of products obtained by powder metallurgy methods. In modern aircraft and rocket engineering, heat-resistant heterophase nickel alloys are used, which are obtained with the use of granular metallurgy. This material is indispensable in the creation of disks of gas turbine engines (GTE), which are part of the turbine rotor and serve to install the blades. Obtaining a nonporous product made of EP741NP alloy using the HIP technology will increase the service life of the turbine disks, which is an urgent task at the present time. The aim of the work is to study the structure and physical and mechanical properties of a billet made of heat-resistant nickel alloy EP741NP obtained by the HIP method at a temperature of 1150 °C. The starting material for the preparation of the workpiece is a metal powder EP741NP, obtained by gas atomization and having a fractional composition of 20...50 microns. It is shown that the HIP process at a temperature of 1150 °C makes it possible to obtain an optimal combination of physical and mechanical properties. Based on the obtained images of powder particles and the microstructure of the work piece, the shape of the particles of the powder under study, the main category of powder granularity was determined and digital porosity analysis of the workpiece under study was performed in the Thixomet Pro software package. The changes in density and hardness along the section of the work piece were also evaluated. It has been established that at a temperature of HIP 1150 °, the average porosity is insignificant and is 0.1 %, however, as we move away from the edge of the workpiece to its center, there is an increase in the content of pores, the size of which lies in the range of 1...20 microns. It is shown that during the technological process of HIP, an arched effect is observed, the consequence of which are overestimated characteristics of microhardness and density at the edge of the work piece.

Encapsulation of radioactive stainless-steel corrosion products sludge in aluminum using hot isostatic pressing process and treatment suitability assessment

Sludge powder with stainless-steel corrosion products generated from the long-term contaminated-waste fluid tank of a nuclear power plant was compressed into a cylindrical shape by a hydraulic press at room temperature. The cylindrical sludge was wrapped in molten Al in a carbon crucible and cooled and hardened at room temperature. Subsequently, the encapsulated sludge was heated and compressed by the hot isostatic pressing (HIP) process. The Al capsule was melted and separated from the cylindrical solidified sludge. In solidified sludge, the leachability indices of Co, Fe, Cr, and Ni were 17.5 ± 0.0736, 13.4 ± 0.0952, 11.2 ± 0.0952, and 16.9 ± 0.0739, respectively. This satisfies Korea's criterion for the disposal of solidified radioactive waste, which is a leachability index of more than 6.

Hot corrosion behavior of hot isostatic pressing treated TiC/GTD222 composite fabricated by selective laser melting

Purpose This paper aims to design a novel TiC/GTD222 nickel-based high-temperature alloy with excellent hot corrosion resistance by incorporating appropriate amounts of C, Al and Ti elements into GTD222 alloy. Design/methodology/approach The composite material was prepared using the selective laser melting (SLM) technology, followed by a hot isostatic pressing (HIP) treatment. Subsequently, the composite underwent a hot corrosion test in a 75% Na2SO4 + 25% NaCl mixed salt environment at 900 °C. Findings The HIP-SLMed TiC/GTD222 composite exhibits a relatively low weight loss rate. First, the addition of alloying elements facilitates the formation of multiple protective oxide films rich in Al, Ti and Cr. These oxide films play a crucial role in enhancing the material’s resistance to hot corrosion. Second, the HIP treatment results in a reduction of grain size in the composite and an increased number of grain boundaries, which further promote the formation of protective films. Originality/value The hot corrosion behavior of the TiC/GTD222 nickel-based composite material prepared through SLM and HIP processing has not been previously studied. This research provides a new approach for designing nickel-based superalloys with excellent hot corrosion resistance.

Hot Work Mold Repaired via Hot Isostatic Pressing towards High Red Hardness

Repairing hot work molds can extend their lifespans and reduce the production costs. This study presents a proposed method for enhancing the red hardness and strength of repaired molds. The method involves utilizing PM23 high-speed steel powder to repair H13 steel molds with two distinct surface states through the process of hot isostatic pressing (HIP). The internal microstructure changes, bonding state, fracture morphology, and crack extension behaviors of the repaired molds are characterized using scanning electron microscopy and electron backscatter diffraction technology. Additionally, the mechanical properties, including red hardness and tensile strength, are quantitatively analyzed. The findings indicate that the repaired area in the sandblasted sample exhibits a rough and uneven structure, demonstrating exceptional toughness. The tensile strength of the repaired region is approximately 1195.42 MPa, while the hardness measures around 672.8 HV. These properties effectively enhance the performance of the molds. The experimental findings indicate that HIP can effectively restore molds, resulting in enhanced red hardness and improved toughness, particularly when combined with sandblasting as a pretreatment method.

Micro X-ray computed tomography examination of mini plate fuel with hot isostatic pressed aluminum cladding

In order to minimize proliferation risks and improve security of nuclear material, the United States high performance research and test reactors (USHPRR) program is tasked with converting nuclear reactors that are fueled with highly enriched uranium (HEU) fuels to operate with low-enriched uranium (LEU) nuclear fuels. One favorable LEU fuel configuration is plate fuel with a metallic uranium-molybdenum foil clad within an aluminum alloy (AA 6061). In this fuel, the aluminum cladding is bonded with a hot isostatic pressing (HIP) method to seal the cladding around the fuel meat. However, the HIP process parameters influence the cladding performance, as a defective or incomplete bond can cause a pathway for corrosion. Micro X-ray computed tomography (XCT), a nondestructive technique that provides volumetric imaging, can be applied to inspect fuel plate cladding at the engineering scale. In this work, XCT methodology was developed and successfully utilized to not only observe the bond line of unirradiated mini fuel plates, but to also identify subsurface abnormalities in the plates’ cladding. In future work, this technique could be applied to fuel plates, pre- and post-irradiation, to quantify irradiation effects on cladding defects and bond line integrity.

Application of the powder filler and hot isostatic pressure process to bond the hybrid structured Ni-based superalloy pieces

This study employed hot isostatic pressing (HIP) to bond directionally solidified (DS) and fine equixed grain (FEG) hybrid structured rods (CM247LC Ni-based superalloy). The bonding was facilitated using an intermediated layer (IL) formed by CM247LC powder filler. The preselected parameters for the HIP process were established based on an earlier study. The bonded samples were heat-treated to achieve the optimal strength of the bonded pieces.The test results revealed that carbides γ’ and eutectic γ-γ’ in the DS and FEG pieces coarsened after the HIP process. Following heat treatment, notable changes were observed in both DS and FEG. The grain size and volume fraction of the carbides and γ-γ’ decreased, while γ’ became a typical diced-shape phase. The IL area has the finest γ matrix grain size compared to DS and FG. In addition to the diced cube shape γ’, γ-γ’ was hardly observed. Furthermore, the nano- or sub-micro-sized carbides were evenly distributed within the matrix and grain boundaries, which was crucial in inhibiting fracture accumulation during tensile tests. Therefore, following the tensile tests, the fracture location tended to occur in the DS piece. This occurrence could be attributed to the DS having the largest matrix grain, the presence of the γ-γ’, and the largest-sized carbides.

Properties of Padding Welds Made of CuAl2 Multiwire and CuAl7 Wire in TIG Process.

This paper presents the influence of the Hot Isostatic Pressing (HIP) process on the structure, mechanical properties and corrosion resistance of padding welds made using the TIG method from aluminium bronzes-CuAl7 and CuAl2 (a composite bundled wire). The tested CuAl7 material was a commercial welding wire, while the CuAl2 composite was an experimental one (a prototype of the material produced in multiwire technology). The wire contains a bundle of component materials-in this case, copper in the form of a tube and aluminium in the form of rods. The padding welds were manufactured for both the CuAl7 wire and the CuAl2 multiwire. The prepared samples were subjected to the Hot Isostatic Pressing (HIP) process, chemical composition tests were performed, and then the samples were subjected to observations using light microscopy, Vickers hardness testing, electrical conductivity tests, and apparent density determination using Archimedes' Principle. Tribological tests (the 'pin on disc' method) and neutral salt spray corrosion tests were conducted. The padding weld made of CuAl2 multifiber material subjected to the HIP process is characterized by an improvement in density of 0.01 g/cm3; a homogenization of the hardness results across the sample was also observed. The average hardness of the sample after the HIP process decreased by about 15HV, however, the standard deviation also decreased by about 8HV. The electrical conductivity of the CuAl2 welded sample increased from 16.35 MS/m to 17.49 MS/m for the CuAl2 sample after the HIP process. As a result of this process, a visible increase in electrical conductivity was observed in the case of the wall made of the CuAl2 multiwire-an increase of 1.14 MS/m.

Influence of processing on secondary phase formation and microstructural evolution at U-10Mo alloy and Zr interlayer interfaces

Thermo-mechanical processing of uranium-10 wt% molybdenum (U-10Mo) alloy fuel plates with a zirconium (Zr) interlayer leads to microstructure changes at fuel/interlayer interfaces. Secondary phases formed at this interface are particularly important to interfacial bond strength, process optimization, and maintaining structural integrity of the fuel plates during irradiation. In this work, we determined the phases and phase transformation products occurring at the interface of the U-10Mo fuel and Zr interlayer when fuel plates are subjected to short and long hot isostatic pressing (HIP) cycles. Interfacial morphology, crystal structure and composition of phases formed, and relative hardness across the U-10Mo/Zr interfaces were studied using a multi-length scale, multi-modal characterization approach involving electron microscopy, atom probe tomography, and atomic force microscopy. Results highlight that the extent of phase transformations, secondary phase formation, and hardness variability across interfaces can be controlled by modifying processing parameters. In addition, phases formed at U-10Mo/Zr interfaces are similar for both HIP process conditions, however, phase distribution, interface thickness, and relative hardness vary significantly. The extent of the discontinuous precipitation reaction leading to α-U formation is also impacted by temperature and pressure in the HIP step; greater time at elevated temperature/pressure increases extent of the DP reaction.

Research on hot isostatic pressing sintering behavior of 90W–Ni–Fe–Cu alloy

In order to understand the underlying material evolution during liquid phase sintering (LPS) process in hot isostatic pressing process (HIP), microstructure and mechanical properties of 90 W–Ni–Fe–Cu alloys fabricated at 1400 °C/150 MPa are examined systematically. For 90W-4.2Ni-1.8Fe–4Cu alloy, the typical LPS microstructure, which are spherical W grains uniformly surrounded by continuously distributed γ- (Ni, Fe, Cu) matrix phase with the lowest W–W contiguity of 0.31, is achieved successfully after HIP at 1400 °C/150 MPa. The excellent tensile strength reaches as high as 873 MPa with elongation of 17.3% due to the soft γ- (Ni, Fe, Cu) matrix phase. Moreover, the relationship between the microstructure parameters VM(1−CW−W) and elongation ε are established and analyze the association with dislocation motion in depth through electron backscattered diffraction (EBSD) characterization. To our best knowledge, the LPS behavior of tungsten alloy is in-situ revealed by high-temperature confocal scanning laser microscopy (HT-CSLM) for the first time. The current research provides a novel strategy for designing and fabricating powder metallurgy materials by LPS with pressure.

Effect of hot isostatic pressing on the mechanical and corrosive properties of Ti–Ni alloy fabricated by selective laser melting

Hot isostatic pressing (HIP) is capable of mitigating the internal defects of materials, such as pores and cracks, resulting in improved mechanical properties and corrosion resistance, so it is particularly suitable as a post-treatment technology for the Ti–Ni alloys fabricated by selective laser melting (SLM), which display a broad application prospect in the biomedical field. Herein, the effect of HIP treatment on the mechanical and corrosion-resistant properties of SLM Ti–Ni alloys was systematically investigated. It was demonstrated that HIP treatment did not substantially affect the phase transformation behavior of the SLM Ti–Ni alloy, only showing a slight decrease in the values of As and Ms. However, HIP treatment improved the ultimate tensile strength and the elongation to fracture of the SLM Ti–Ni alloy by 67.3% and 23.2%, respectively. Meanwhile, the corrosion current density was reduced by two orders of magnitude after HIP treatment, indicating the significantly increased corrosion resistance. The enhanced mechanical properties and corrosion resistance of SLM Ti–Ni alloy were credited with the elevated temperature and pressure applied during the HIP process, which significantly eliminated the porosity defects and made the microstructure more uniform. These findings highlight the importance of performing HIP to enhance the comprehensive properties of SLM Ti–Ni alloys, which can expand the application prospects of SLM Ti–Ni alloys in the biomedical field.

Microstructure of TiAl Capsules Processed by Electron Beam Powder Bed Fusion Followed by Post-Hot Isostatic Pressing.

The microstructures of intermetallic γ-titanium aluminide (TiAl) alloys are subjected to a certain degree of Al evaporation when processed by electron beam powder bed fusion (EB-PBF). The magnitude of the Al-loss is mainly correlated with the process parameters, and highly energetic parameters produce significant Al evaporation. The Al-loss leads to different microstructures, including the formation of inhomogeneous banded structures, thus negatively affecting its mechanical performance. For this reason, the current work deals with creating EB-PBFed TiAl capsules with the inner part produced using only the pre-heating step and melting parameters with low energetic parameters applying high beam speed from 5000 to 3000 mm/s. This approach is investigated to reduce the Al-loss and microstructure inhomogeneity after hot isostatic pressing (HIP). The results showed that the HIP treatment effectively densified the capsules obtaining a relative density of around 100%. After HIP, the capsules produced with the inner part melted at 3000 mm/s presented a lower area shrinkage (around 6.6%) compared to the capsules produced using only the pre-heating step in the core part (around 20.7%). The different magnitudes of shrinkage derived from different levels of residual porosity consolidated during the HIP process. The HIPed capsules exhibited the presence of previous particle boundaries (PPBs), covered by α2 phases. Notably, applying low energetic parameters to melt the core partially eliminates the particles' surface, thus reducing the PPBs formation. In this case, the capsules melted with low energetic parameters (3000 mm/s) exhibited α2 concentration of 3.5% and an average size of 13 µm compared to the capsules produced with the pre-heating step in the inner part with an α2 around 5.7% and an average size around 23 µm. Moreover, the Al-loss of the capsules was drastically limited, as determined by X-ray fluorescence (XRF) analysis. More in detail, the capsules produced with the pre-heating step reported an atomic percentage of Al of 48.75, while using low energetic melting parameters led to 48.36. This result was interesting, considering that the massive samples produced with standard parameters (so more energetic ones) revealed atomic Al percentage from 48.04 to 47.70. Finally, the recycled small particles showed a higher fraction of α2 phases with respect to the coarse particles, as determined by X-ray diffraction (XRD).