Hot Isostatic Pressing Research Articles

Optimization of Yb:CaF2 Transparent Ceramics by Air Pre-Sintering and Hot Isostatic Pressing

Yb:CaF2 transparent ceramics represent a promising laser gain medium for ultra-short lasers due to their characteristics: low phonon energy, relatively high thermal conductivity, negative thermo-optical coefficient, and low refractive index. Compared to single crystals, Yb:CaF2 ceramics offer superior mechanical properties, lower cost, and it is easier to obtain large-sized samples with proper shape and uniform Yb3+ doping at high concentrations. The combination of air pre-sintering and Hot Isostatic Pressing (HIP) emerges as a viable strategy for achieving high optical quality and fine-grained structure of ceramics at lower sintering temperatures. The properties of the powders used in ceramic fabrication critically influence both optical quality and laser performance of Yb:CaF2 ceramics. In this study, the 5 atomic percentage (at.%) Yb:CaF2 transparent ceramics were fabricated by air pre-sintering and hot isostatic pressing (HIP) using nano-powders synthesized through the co-precipitation method. The co-precipitated powders were optimized by studying air calcination temperature (from 350 to 550 °C). The influence of calcination temperature on the microstructure and laser performance of Yb:CaF2 ceramics was studied in detail. The 5 at.% Yb:CaF2 transparent ceramics air pre-sintered at 625 °C from powders air calcined at 400 °C and HIP post-treated at 600 °C exhibited the highest in-line transmittance of 91.5% at 1200 nm (3.0 mm thickness) and the best laser performance. Specifically, a maximum output power of 0.47 W with a maximum slope efficiency of 9.2% at 1029 nm under quasi-CW (QCW) pumping was measured.

Full Density Powder Metallurgical Cold Work Tool Steel through Nitrogen Sintering and Capsule-Free Hot Isostatic Pressing

Vanadis 4E (V4E) is a powder metallurgical cold work tool steel predominantly used in application with demand for wear resistance, high hardness, and toughness. It is of interest to have a processing route that enables full density starting from clean gas-atomized powder allowing component shaping capabilities. This study presents a process involving freeze granulation of powder to facilitate compaction by means of cold isostatic pressing, followed by sintering to allow for capsule-free hot isostatic pressing (HIP) and subsequent heat treatments of fully densified specimens. The sintering stage has been studied in particular, and it is shown how sintering in pure nitrogen at 1150 °C results in predominantly closed porosity, while sintering at 1200 °C gives near full density. Microstructural investigation shows that vanadium-rich carbonitride (MX) is formed as a result of the nitrogen uptake during sintering, with coarser appearance for the higher temperature. Nearly complete densification, approximately 7.80 ± 0.01 g/cm3, was achieved after sintering at 1200 °C, and after sintering at 1150 °C, followed by capsule-free HIP, hardening, and tempering. Irrespective of processing once the MX is formed, the nitrogen is locked into this phase and the austenite is stabilised, which means any tempering tends to result in a mixture of austenite and tempered martensite, the former being predominate during the sequential tempering, whereas martensite formation during cooling from austenitization temperatures becomes limited.

Defect recrystallization in subtransus hot isostatic pressing of electron beam powder bed fusion Ti-6Al-4V

Post-build hot isostatic pressing (HIP) is a widely used method to close as-built defects (gas or lack-of-fusion porosity) in additively manufactured (AM) metal parts. Pore closure during this process often creates clusters of equiaxed grains, in contrast to coarse and directional as-built microstructures widely seen in AM metals. Understanding the mechanisms behind the formation of such microstructures is desirable for controlling anisotropy and improving mechanical properties of AM parts. Prior work has attributed defect-induced equiaxed grains to recrystallization during the HIP process; however the specifics of this recrystallization process have not been explored. This work systematically analyzes the grain structure, orientation, and misorientations of electron beam powder bed fusion (PBF-EB) Ti-6Al-4V to identify the mechanisms by which clusters of equiaxed grains can form during HIP of as-built microstructures. A combination of two mechanisms, dynamic recovery (DRV) and continuous dynamic recrystallization (CDRX), explains the phenomena. Evidence for both these processes is found in small rotations in crystallographic orientation, localized strains around prior pore defects, and specific misorientation distributions. Only subtransus HIP of Ti-6Al-4V was explored in this work. However, the mechanisms presented here are thought to contribute to recrystallization in other HIP processes whether for super-transus Ti-6Al-4V, β-Ti alloys, other alloy systems, or non PBF-EB build processes. These results build upon prior efforts to identify specific mechanisms by which refined microstructures can be achieved in as-HIPed AM metals, improving microstructural control and providing another pathway for microstructural tailoring via AM of metals.

Microstructure and mechanical properties of hybrid hexagonal BN nanotube and nanoplatelet reinforced AZ91 Mg matrix composites

In this research, we report fabrication of AZ91 (Mg–Al–Mn–Zn) matrix composites reinforced with a hybrid of hexagonal boron nitride nanoplatelets (BNNP) and nanotubes (BNNT) using spark plasma sintering (SPS) and hot isostatic pressing (HIP). The resultant composites present dense microstructure featured by the refined α-Mg grains decorated with eutectic along the α-Mg grain boundaries, and trace amounts of in-situ interfacial-reaction products such as Mg3N2 and MgB2 are observed to serve as chemical anchors for stronger interface. More importantly, the AZ91 composites reinforced with a hybrid of 0.4 wt% BNNPs-0.1 wt% BNNTs displays ∼209 MPa of compressive yield strength, ∼329 MPa of ultimate compressive strength and ∼19.4% of elongation, achieving satisfactory balance of strength and ductility when compared to the AZ91 composite reinforced with sole BNNPs. This improvement can be attributed to the unique three-dimensional hybrid structure, where BNNPs maintain their high specific surface area, and the de-bundled BNNTs extend like tentacles, further contributing to their interfacial adhesion with the matrix. This research is expected to pave the way for the development of Mg-based composites with an optimal balance of strength and ductility.

Mechanical and Fatigue Properties of Ti-6Al-4V Alloy Fabricated Using Binder Jetting Process and Subjected to Hot Isostatic Pressing.

Binder jetting 3D printing is an additive manufacturing technique based on the creation of a part through the selective bonding of powder with an adhesive, followed by a sintering process at high temperature to densify the material and produce parts with acceptable properties. Due to the high initial porosity in the material after sintering, which is typically around 5%, post-sintering treatments are often required to increase the material density and enhance the mechanical and fatigue properties of the final component. This paper focuses on the study of the benefits of hot isostatic pressing (HIP) after sintering on the mechanical and fatigue properties of a binder jetting Ti-6Al-4V alloy. Two different HIP processes were considered in this study: one at 920 °C/100 MPa for 4 h, and a second at a higher pressure but lower temperature (HIP-HPLT) at 850 °C/200 MPa for 2 h. The effects of the HIP on the densification, microstructure, mechanical behavior, and fatigue properties were investigated. The results show that the HIP-HPLT process produced a significant increase in the mechanical and fatigue properties of the material compared with the as-sintered parts and even with the conventional HIP process. However, the fatigue and fracture micromechanisms suggest that the oxygen content, which resulted from the decomposition of the binder during the sintering process, played a critical role in the final mechanical properties. Oxygen could reduce the ductility and fatigue life, which deviated from the behavior observed in other additive manufacturing techniques, such as powder bed fusion (PBF).

Advances in Nickel-Containing High-Entropy Alloys: From Fundamentals to Additive Manufacturing.

High-entropy alloys (HEAs) are recognized as a class of advanced materials with outstanding mechanical properties and corrosion resistance. Among these, nickel-based HEAs stand out for their impressive strength, ductility, and oxidation resistance. This review delves into the latest advancements in nickel-containing HEAs, covering their fundamental principles, alloy design strategies, and additive manufacturing techniques. We start by introducing HEAs and their unique properties, emphasizing the crucial role of nickel. This review examines the complex relationships between alloy composition, valence electron concentration (VEC), and the resulting crystal structures. This provides insights into design principles for achieving desired microstructures and mechanical properties. Additive manufacturing (AM) techniques like selective laser melting (SLM), electron beam melting (EBM), and laser metal deposition (LMD) are highlighted as powerful methods for fabricating intricate HEA components. The review addresses the challenges of AM processes, such as porosity, fusion defects, and anisotropic mechanical properties, and discusses strategies to mitigate these issues through process optimization and improved powder quality. The mechanical behavior of AM-processed nickel-based HEAs is thoroughly analyzed, focusing on compressive strength, hardness, and ductility. This review underscores the importance of microstructural features, including grain size, phase composition, and deformation mechanisms, in determining the mechanical performance of these alloys. Additionally, the influence of post-processing techniques, such as heat treatment and hot isostatic pressing (HIP) on enhancing mechanical properties is explored. This review also examines the oxidation behavior of nickel-containing HEAs, particularly the formation of protective oxide scales and their dependence on aluminum content. The interplay between composition, VEC, and oxidation resistance is discussed, offering valuable insights for designing corrosion resistant HEAs. Finally, this review outlines the potential applications of nickel-based HEAs in industries such as aerospace, automotive, and energy, and identifies future research directions to address challenges and fully realize the potential of these advanced materials.

Effect of the cooling behavior on phase transformation and mechanical property of RAFM steel

The phase transition behavior of RAFM steel during Hot Isostatic Pressing (HIP) diffusion bonding process would extensively impact the service performance of blanket component in the future fusion reactor. In this paper, the influence of cooling behavior on phase transformation and mechanical property of RAFM steel was studied using a combination of Electron Backscatter Diffraction (EBSD) and a thermal dilatometer. The results show that as the cooling rate decreases after austenitizing, the phase category transitions from a single-phase of martensite to the dual-phase of martensite and ferrite, along with an increase in the rate of ferrite, minor martensite packets and high-angle grain boundaries (HAGB). As the cooling rate decreases, the initial temperature for martensite transformation significantly increases, and the transformation driving force slowdown. Moreover, specimens processed with HIP cooling show lower strength, higher elongation, and a greater standard deviation of hardness compared to air cooling. These differences can be attributed to the formation of ferrite and the diffusion of carbon atoms within martensite. The research findings reveal the phase transition and microstructural evolution of martensite under varying cooling conditions, providing a reference for the controlling the cooling process after HIP bonding of blanket steel components in the future fusion reactor.

Development and manufacturing of beryllium-armoring ITER enhanced heat flux FW toward series production in China

ITER’s enhanced heat flux (EHF) first wall (FW) provides thermal shielding to the other components behind it and limits its plasma boundary, consequently bearing high surface heat loads up to 4.7 MW m−2. China developed the EHF FW technologies in steady stages by making small mock-ups, semi-prototypes and a full-scale prototype (FSP), working toward series production at the Southwestern Institute of Physics. All the key technologies for bimetallic diffusion bonding, welding and assembly have been fully qualified. The Be armor tile size effects on thermal-fatigue performance have been evaluated using a pulsed high heat flux test with an EMS-400 electron beam facility. It was found that both the Be/CuCrZr bonding and its thermal-fatigue life are highly dependent on the tile size, and 12 × 12 mm2 Be tiles are acceptable for the required performance, either as individual tiles or in castellation by cutting larger ones. Small-scale mock-ups with such Be tiles survived 16 000 thermal cycles at 4.7 MW m−2, while EHF FW fingers with 16 × 16 mm2 Be tiles demonstrated unstable performance. In contrast, only BE tiles larger than 24 × 12 mm2 showed reliable diffusion bonding with the CuCrZr heat sink by hot isostatic pressing and consequently should be castellated into smaller ones. The manufacturing of the FSP finger goes through complex thermal cycles, using CuCrZr alloys in age-strengthening plus cold-rolling states, enabling it to maintain its tensile strength to the level of 285 MPa and its mean grain size less than 100 µm. The pipe welding for finger pairing and its assembly with the central beam are demonstrated, including enabling welding to be carried out twice for repair in a narrow space. The FSP showed good finger alignment, dimensional control and reliable vacuum tightness without any blockage of cooling channels.

High-temperature microstructure evolution and thermal stability of SiCf/Ti60 composites

The microstructure evolution and thermal stability of continuous SiC fiber-reinforced Ti60 (SiCf/Ti60) composites at elevated temperatures have not been reported. The objective of this study was to conduct thermal exposure experiments of SiCf/Ti60 composites at 400 °C / 100 h, 600 °C / 100 h, and 800 °C / 100 h. The aim was to compare the interfacial and matrix microstructures under hot isostatic pressure (HIP) conditions and to assess their thermal stability. The results show that SiCf/Ti60 composites have excellent long-term thermal stability at 600 °C thermal exposure, short-term thermal stability at 800 °C thermal exposure and the thickness of the reaction layer (RL) increases to ∼1.27 μm. From HIP to 800 °C thermal exposure, RL changes from fine-grained TiC ║ discontinuous silicides ║ coarse-grained TiC to fine-grained TiC ║ near-continuous silicides ║ medium-grained TiC ║ coarse-grained TiC. Large-sized β-Ti and S2 silicides precipitated in the matrix at 800 ℃ thermal exposure, where β-Ti and α-Ti followed the Burgers orientation relationship (BOR), and the S2 exhibited a multitude of orientation relationships with both β-Ti and α-Ti. Furthermore, it was demonstrated that thermal exposure resulted in a reduction in the dislocation density of the matrix. In particular, thermal exposure at 800 °C led to a decrease in the dislocation density of the matrix by ∼47 %. This observation provided a novel approach for the reduction of crystal defects in the matrix and the enhancement of the properties of SiCf/Ti composites.

Improving the fatigue life of laser powder bed fusion Scalmalloy® by friction stir processing

A major concern about parts produced by laser powder bed fusion (L-PBF) are intrinsic defects or porosities that are difficult to overcome by simply optimizing the process parameters. As these defects and porosities play a crucial role in the mechanical behaviour, especially in fatigue, additive manufactured parts are often subjected to thermo-mechanical post-treatments. To this end, this work proves Friction Stir Processing (FSP) to be an effective post-treatment to drastically reduce the porosity level. FSP leads to an improvement of 60 % of the technical fatigue strength and by two orders of magnitude of the fatigue life of L-PBF Scalmalloy® specimens. The fatigue performances obtained on FSPed and heat-treated specimens are equivalent or even better than the best fatigue life reported in the literature, whatever their L-PBF conditions and post-treatments, while avoiding Hot Isostatic Pressing. However, FSP reduces the beneficial effect of the conventional strengthening heat-treatment applied to L-PBF Scalmalloy®, lowering the high tensile strength for which the alloy is normally reputed. Advanced characterisation by X-ray microtomography and Transmission Electron Microscopy allows us to reach a better understanding of the involved phenomena: drastic reduction of the biggest defects and heterogeneous nucleation of Sc- and Zr-rich precipitates on grain boundaries and dislocations.

Formation mechanism of TiC twin during densification of SiCf/Ti2AlNb composites

SiCf/Ti2AlNb composites were fabricated using the magnetron sputtering precursor wires method in conjunction with the hot isostatic pressing (HIP) technique. The morphology, elemental distribution, and structural characteristics of the interfacial reaction layer (RL) were examined through scanning electron microscopy (SEM), transmission electron microscopy (TEM), and wavelength dispersive spectroscopy (WDS). The results showed that the interface between SiC fibers and Ti2AlNb reacted to form TiC and α2. Due to the interdiffusion of elements at the interface, a small amount of Al atoms existed in the TiC layer. These Al atoms reduced the stacking fault energy (SFE) of TiC, which is beneficial for the formation and stability of Σ3{111} twin boundaries.

Microstructure and properties of hot isostatic pressed/laser remelted Fe3Al/Cr3C2 composites

The effects of Cr3C2 content on the microstructure, hardness and wear resistance of Fe3Al/Cr3C2 composites by hot isostatic pressing and laser remelting were studied. The results showed that, the carbides in the hot isostatic pressed (HIPed) Fe3Al/Cr3C2 composites are in large block or irregular shape, while the in situ formed carbides in the laser remelted (LRed) Fe3Al/Cr3C2 composites are small and dispersed. With the increase of Cr3C2 content, the microhardness of HIPed and LRed Fe3Al/Cr3C2 composites gradually increased, and the microhardness of LRed Fe3Al/Cr3C2 composites is higher than that of HIPed ones. With the increase of Cr3C2 content, the wear resistance of HIPed Fe3Al/Cr3C2 composites increased gradually, while the wear resistance of LRed Fe3Al/Cr3C2 composites first increases and then decreases, and the best wear resistance is obtained when the volume fraction of Cr3C2 is 18%.

Solution temperature influence on CRSS of the secondary γ′ phase in nickel-based superalloy FGH4096

Nickel-based superalloy components are capable of being manufactured by direct hot isostatic pressing (HIP) process with near-net shape and nearly 100 % raw materials utilization. However, they cannot be applied directly, due to the poor mechanical properties of HIPed components. Fortunately, heat treatment can improve the properties via regulating the microstructure. Therefore, the effects of varied solution temperatures on the tensile properties of FGH4096 nickel-based superalloy disk at room and high temperatures were studied. The results revealed that the disk after sub-solution treatment (1130 °C) has higher tensile properties (room temperature yield strength: 1194 MPa, elongation: 15.5 %; high temperature yield strength: 1075 MPa, elongation: 10.5 %). The antiphase boundary (APB) shear stress, Orowan bypass stress, stacking faults (SF) shear stress, and micro-twins (MT) shear stress affected by the size and distribution of the secondary γ′ phase were calculated. The results show that the main strengthening mechanism at room temperature is APB shear, and the APB shear stress of solution treatment at 1190 °C is the highest. The high temperature strengthening mechanism is due to SF shear and MT strengthening effects. The difference in SF shear stress between various solution temperatures is minimal. 1190 °C has a higher MT strengthening effect than 1090 °C. This is consistent with the actual result that the tensile properties at 1190 °C are superior to those at 1090 °C. The conclusion is that the combination of high strength reflected by several critical resolved shear stresses and considerable plasticity reflected by the MT strengthening effect can lead to a comprehensive improvement in alloy tensile properties.

Effect of hot isostatic pressing on microstructure and properties of cooled hot dip aluminum coating in magnetic field

The effect of hot isostatic pressing (HIP) on the microstructure and properties of hot dip aluminum coating cooled in a magnetic field was investigated in this study. In order to improve the microstructure and properties of magnetic dip aluminum coating, hot isostatic pressing technology was used for post-treatment. Initially, a traditional aluminum-impregnated coating was prepared on the surface of titanium alloy TA15, an alternating electromagnetic field was applied during the forming and solidification process of the coating. Finally, the coating was treated with hot isostatic pressing technology. Analyzed three different coatings of the microstructure and element distribution, and tested the microhardness of the coatings at various positions. The test results revealed that the TA15 titanium alloy hot-dip aluminum coatings obtained through the three different processes exhibited a gradient structure. Compared with the traditional hot-dipped aluminum air-cooled coating, when an appropriate intensity of alternating electromagnetic field was applied during the coating solidification process, the outer coating structure was enhanced, the number of holes was reduced, the microstructure density increased, and the number of cracks significantly decreased. The defects of the 800 °C hot isostatic magnetic cold and hot dip aluminum coating were repaired under high temperature and pressure, resulting in a uniform and fine microstructure. The comprehensive properties of the magnetic cold and hot dip aluminum coating on the surface of the titanium alloy were effectively enhanced through hot isostatic pressing.

Superior uniform deformation ability of intragranular nano TiB reinforced Ti-6.5Al–2Zr–Mo–V fabricated by hot isostatic pressing

In order to improve the uniform deformation ability of titanium matrix composites, the intragranular nano-TiB whiskers (TiBnw) reinforced Ti-6.5Al–2Zr–1Mo–1V (TA15) composite was designed and fabricated by hot isostatic pressing (HIP) at the temperature of 1000 °C. The TiBnw was successfully planted into the pre-alloyed powders before HIP. The composite sintered for 6h (HIP-6h) realized a complete densification process benefiting from a high sintering pressure of 150 MPa. While the 2h sintering process (HIP-2h) was insufficient to densify. The HIP-6h exhibited an unparalleled uniform elongation of 9.5 %, which was superior to the survey TA15 matrix titanium composites. The excellent uniform deformation ability was demonstrated to be associated with the equiaxed structure and the blocking and multiplication effect on dislocations from the intragranular TiBnw.

High strength and fatigue performance achieved for L-PBF processed hybrid particle reinforced Al-Cu-Mg composite

This study highlights the successful manufacturing of a crack-free, dense, hybrid ex-situ/in-situ particle reinforced (Ti + B4C)/Al-Cu-Mg composite, fabricated by laser powder bed fusion and exhibiting exceptional mechanical performance. In its as-built (AB) state, the composite displays a unique microstructure characterized by equiaxed grains with an average grain size of 1.0 ± 0.3 μm, notable interdendritic microsegregation of Cu, Mg, Mn, and Fe, randomly distributed ex-situ added Ti and B4C particles featuring a surface interaction layer with the metal matrix, and in-situ formed reinforcing particles, such as TiB2 and TiC. After subjecting the material to hot isostatic pressing (HIP) and subsequent aging treatment, dissolution of interdendritically segregated elements occurs, and precipitation of Al2Cu, Al12Mg17, and Al-Fe-Cu-Mn phases is observed. Significantly enhanced fatigue performance is recorded, reaching to 107 cycles at 250 MPa in AB and 330 MPa in HIP state, marking a 32 % improvement. The current study highlights the intricate relationship between the different microstructural features in AB and HIPed state, leading to fracture during tensile and fatigue loading conditions.

New processing routes for Zr-based ODS ferritic steels

In this work, Zr addition is proposed to refine the nanoparticle dispersion in an ODS RAF steel of composition Fe-14Cr-2W-0.3Zr-0.24Y (wt.%). Three batches of material are obtained using pre-alloyed atomized powder, where yttrium is directly introduced in the melt, and manufactured through three different processing routes. First route is based on the newly developed STARS route that aims to avoid subsequent mechanical alloying. The second route explores the impact of mechanical alloying in pre-oxidized powders. The third route uses mechanically alloyed powders without the pre-oxidation process. The ODS-powders were individually consolidated by hot isostatic pressing and later hot rolled. The obtained materials were characterized by small-angle neutron scattering (SANS) and X-ray absorption spectroscopy (XAS) techniques. SANS and XAS analysis point out the absence of oxide nanoparticles in the material based on the STAR route. SANS analysis confirms that the mechanically alloyed materials do exhibit the presence of nanoparticles. These are identified as Zr-O-rich nanoprecipitates by XAS and the calculated A-ratio by SANS is linked with the phase Y2Zr2O7. Their radii are in the range of 3–3.6 nm. XAS results show that mechanical alloying minimizes the initial differences regarding the oxidation state between the ODS powders with and without pre-oxidation.

Effect of hot isostatic pressing on stress-rupture crack growth of a single-crystal nickel-based superalloy

The solution-treated second-generation single crystal (SX) superalloys underwent hot isostatic pressing (HIP) at 1316 °C and 105 MPa for varying durations. This study investigates the effect of HIP on micropores and stress-rupture behavior under conditions of 980 °C and 250 MPa. The results illustrate that the application of HIP treatment significantly reduces the porosity and volume of micropores, thereby increasing the rupture life of the alloys. With the disappearance of micropores, the crack initiation site shifts from the micropores to the γ/γʹ interface, resulting in reduced crack dimensions and decelerated propagation. Consequently, the smaller size of cracks in HIPed specimens slow down fracture. Nonetheless, the crack propagation pattern remains consistent: cracks expand perpendicular to the stress axis, connecting with cracks at other heights via secondary cracks along the <112> direction.

Enhancing mechanical properties and density of WC-Co with pressureless sintering via shell structure binder jetting additive manufacturing

The binder jetting (BJT) additive manufacturing (AM) process is suitable for producing complex WC-Co cemented carbide parts. To achieve near-full-density in the final parts, the hot isostatic pressing (HIP) sintering process is typically employed to enhance densification. However, HIP sintering requires high equipment specifications and is relatively more costly compared to conventional pressureless sintering. To improve the density of WC-Co parts printed by BJT AM under the pressureless sintering environment, the shell structure printing method was used in this study. The shell structure printing only jets binder to the model's outer profile, creating a shell that encapsulates the central powder, mitigates binder pyrolysis and residual effects on particle densification, and enhances post-sintering density. In this work, the effect of shell thickness, binder type, and printing layer thickness on the density and mechanical properties of the WC-12Co parts under pressureless sintering conditions were investigated. The results show that the density and mechanical properties of the WC-12Co parts significantly improved with the decreasing shell thickness. Specifically, the WC-12Co printed using shell structure achieves a relative density of over 98% and a transverse rupture strength (TRS) of 1954 MPa after pressureless sintering, a result comparable to BJT printed samples treated with HIP sintering. Moreover, the results indicate using a binder with lower residual carbon content and smaller printing layer thickness has a more positive effect on improving density and mechanical strength when employing the shell structure printing method. Microstructure morphology and phase analysis results indicate that the shell structure printing method does not affect the growth of WC grains in the shell and center regions, nor does it influence its phase composition. The shell structure printing method offers a new approach to the manufacturing of near-full-dense WC-Co materials using the BJT process.

Effect of boron on the microstructure and performance of HIP-prepared high boron steels

High boron steels containing 2 wt% and 3.3 wt% boron were fabricated using hot isostatic pressing (HIP). The enhanced shielding performance of the steel with higher boron content was quantitatively evaluated through Monte Carlo simulations using software Fluka. The steels were studied with XRD and the phase ratio were calculated using Rietveld refinement method. The microstructure of the materials was investigated using electron backscatter diffraction (EBSD). Comprehensive thermal property measurements, complemented by Hamilton thermal conductivity model analysis, were conducted on high boron steels. The results revealed that the decreased overall thermal conductivity in these materials is primarily attributed to two factors: the increased volume fraction of the boride phase and the enhanced interconnectivity among boride particles. These findings provide crucial insights into the thermal behavior of high boron steels. Room temperature tensile tests indicate that high boron content can cause the fracture mode of the material to transition from ductile to brittle. This study provides a detailed analysis of the effects of boron content on various properties of high boron steels, which can serve as shielding materials in fusion reactors. Advances were proposed for optimizing the thermal performance of high boron steels in this study.