Copper/diamond composites have been proposed as thermal management materials for high performance electronic devices. However, their thermal conductivity (TC) is limited by the weak interfacial bond between the copper and the diamond, due to their poor chemical affinity. To enhance the TC, tungsten (W) was explored as an effective element, reacting with diamond to form a tungsten carbide interface between copper and diamond. This study involved fabricating copper/55vol%W-coated diamond composites via hot forging at temperatures of 800 °C, 950 °C, and 1050 °C. Additionally, annealing of W-coated diamond particles at these temperatures was also conducted to investigate the tungsten carbide interface formation mechanisms on diamond surfaces. The results of the hot-forged composites revealed that the TC of these composites initially increased with rising temperature but then decreased, correlating with distinct phase compositions and interface morphology formed at different hot-forging temperature. Analysis of the annealed W-coated diamond particles found that the reaction temperature for tungstencarbon to form tungsten carbide was above 950 °C, and inner stress at the interface could also contribute to the formation of tungsten carbide during the hot-forging process. Consequently, the optimal interface primarily composed of WC phase with a minor W₂C phase was obtained in 950 °C hot-forged copper/55vol%W-coated diamond composite, and the resultant composite had the highest TC of 432 W/mK. This study offers valuable insights into tungsten carbide interface formation at varying temperatures in copper/W-coated diamond composites, aiding in the selection of the fabrication parameters for future studies.

To modify the surface of practical Mg alloy M1A, M1A laminated compacts were produced by laminating 20vol% Al₂O₃ particle-dispersed Mg mechanical milling (MM) powder (20vol% powder), which has higher hardness than practical Mg alloys, on both surfaces of M1A discs and then spark plasma sintering (SPS) treatment. The results of micro-Vickers hardness tests and wear tests of the M1A laminated compacts showed that the surface coating layer (20vol% layer) had higher hardness, lubricity and wear resistance than the M1A surface, and from optical microscopy lateral observations of the M1A laminated compacts broken by a three-point bending test, the 20vol% layer / M1A interface was found to be highly adherent. Elemental analysis by SEM-EDS and X-ray diffraction results identified the precipitates at the interface as Mn-Al intermetallic compounds. The relationship between the sintering time and the interfacial adhesion suggests that the interfacial adhesion is influenced by the amount of Al diffusion from the 20vol% layer to the M1A disc rather than the formation of Mn-Al intermetallic compounds at the interface.

Aluminum (Al)/carbon composites are considered to be promising thermal management materials in the application field of electronic packaging. In this work, highly densed Al/graphite, Al/carbon fibers (CFs), and Al/graphite/CFs composites were successfully prepared by a hot extrusion process. Besides, small amounts of Al-Si alloy addition and Ni-coating were applied to improve the interfacial bonding between Al matrix and carbon in the composites. The microstructure, thermal conductivity (TC), and coefficient of thermal expansion (CTE) of the hot-extruded Al/carbon composites were investigated. The results showed that hot extrusion can lead to deformation of graphite and align the graphite and CFs along the extrusion direction. Al-Si alloy addition and Ni-coating can effectively improve the Al/carbon interfacial bonding, thus decreasing the interfacial thermal resistance. The Al/graphite composites showed relatively high TC and CTE values, while the Al/CFs composites exhibited relatively low TC and CTE values. In contrast, the Al/graphite/CFs hybrid composites presented an excellent balance between TC and CTE.

Improving sustainability and competitiveness of PM structural parts requires a great deal of focus and efforts. This work shows considerations and solutions based on scientific analysis and estimations¹⁾. Priorities for reduction of energy consumption are sintering, compaction, heat treatment and finish machining. Mainly used in PM alloy systems and base powders (Fe-Cu-C or diffusion-alloyed Fe-Ni-Cu-Mo) require changes in terms of energy consumption, carbon neutrality, material resources and recycling. Availability of fossil free energy, hydrogen, biogas and development of CCS/CCU (Carbon Capture Storage and Utilization) differs in Europe and Japan or from country to country. Various solutions in this work are expected to encourage PM structural parts making industry to shift from theory to practice in order to remain competitive.

Powder metallurgy (PM) manufacturing is known for its cost-effectiveness and ability to produce intricate components, but the sintering process faces challenges due to non-standardized component positioning. This research establishes a framework for sintering automation, focusing on optimizing product positioning within limited space to enhance sintering results. It addresses the Multidimensional Knapsack Problem (MKP) during pre-sintering positioning (see Fig. 1), considering factors like carriers, material properties, process requirements, quality standards, and equipment limitations. The study formulates a visual positioning strategy for pre-sintering, aiding strategic product placement decisions. These patterns and coordinates support machine vision-assisted robotic arms, advancing Intelligent Manufacturing. The findings offer practical solutions for sustainable development and automation in PM manufacturing, effectively addressing real-world production challenges.

A lean Cr-alloy with 0.85wt.% Cr and 0.15wt.% Mo was recently introduced as a Cu-free sustainable alternative PM material. It is always necessary to ensure sufficient hardenability for a selected component and heat treatment process, and with leaner alloys more precautions are necessary. Low-pressure carburising (LPC) combined with gas quenching is preferred for carburising Cr materials, as it avoids oxidation and provides better control over case depth. However, the nature of the gas quenching process requires more alloying to achieve better hardenability compared to oil quenching. In this study to investigate the influence of alloying element on the hardenability, both Ni and graphite were varied between 0 and 2 wt.% and 0.25-0.45 wt.%, respectively for the lean Cr samples. LPC was performed after sintering, and the mechanical performance and hardenability were evaluated. In addition, using simulations, geometry aspects necessary to fulfil the hardenability requirement for high performances were explored to be able to optimise the alloying content for a given application.

Powder metallurgy is an alternative to produce microstructures of materials able to reduce friction and wear of mechanical systems, consequently, improving its efficiency and mitigating CO₂ emissions. In this work, self-lubricating composites were produced using a Fe-based matrix (Fe+0.5Si+4Ni+0.5Mo+0.2Mn) and solid lubricants (1h-BN+6.5graphite) dispersed through the bulk. Thermodynamics aspects were considered to avoid the diffusion of solid lubricants during the sintering and kept them as solid lubricant reservoirs. The samples were characterised in terms of microstructure and mechanical properties. Additionally, its tribological behaviour was analysed in dry and oillubricated conditions (ball-on-cylinder tribopair). Wear marks were analysed to identify the formation of tribolayers and the interaction of composite with the oil and atmosphere. The results indicate a material with outstanding mechanical properties (276.1±50.55 MPa UTS, 770±65 HV_0.05) able to reduce friction and wear due to the formation of tribolayers in both conditions.

The use of recyclable, non-toxic and non-critical alloying elements has become increasingly important in the last years. In particular, the volatile prices of Ni and Cu, and the increasing demand for these elements from the electromobility sector can eventually boost the prices, eliminating the price-competitiveness advantage of PM-steels. This work shows the newest advances in the investigation of PM-steels produced from more sustainable base powder alternatives (such as Astaloy CrS), combined with Fe-Mn-Si-based masteralloys (i.e. a hybrid-alloy approach). Chemical analysis, CCT diagrams and mechanical properties are presented for steels with different hybrid compositions, sintered and heat-treated under different conditions. The results show how, by properly adapting the starting materials and sintering conditions, and by combination with sinter hardening treatments, the use of more sustainable alloy compositions could be extended to additional PM application areas.

Cost-efficient manufacturing of high-performance components requires mix solutions with high apparent density (AD) and good fillability. This is especially critical for taller and more complex-shaped components, where powder solutions with higher AD and consistent die filling are crucial. Traditionally, metal-stearate lubricants have been used to obtain high AD. However, these lubricants provide not only high AD but also often leave stains on sintered parts and residues in the sintering furnace. Höganäs’ new bonded mix solution, Starmix Nova, is developed to offer high AD and excellent filling performance without using metal stearates.This study is based on laboratory experiments and compaction trials in production environments. Compared to a standard Premix with amide wax, Starmix Nova mixes achieve 0.3 g/cm³ higher AD, equivalent to a Premix containing Zn stearate, while exhibiting faster flow and better lubrication. In production trials, Starmix Nova mixes have shown improved component-weight consistency and increased productivity

In this study, the effects of tempering on the mechanical properties and microstructure of chromium-containing low-alloy steel following sintering were investigated. Tempering is typically employed to reduce brittleness and relieve residual stresses in sintered steels when quenching process is applied. Depending on the amount of graphite added, products manufactured from chromium-containing low-alloy steel powder (Fe -3% Cr -0.5% Mo) may require subsequent tempering after sintering to promote the formation of a martensitic microstructure.

The production process aimed at achieving a martensitic structure involved both traditional belt furnace sintering with the addition of copper powder and sinterhardening without copper addition. The atmosphere and temperature during tempering were varied to evaluate their effects.

When the tempering temperature was below 600 K, no significant oxidation was observed, even when tempering was conducted in air. Furthermore, when copper was added to the chromium-containing material through traditional sintering, the material exhibited higher impact energy after tempering compared to the sinterhardened chromium-containing material without copper addition.

At a tempering temperature of approximately 500 K, the tensile strength and impact energy reached approximately 1200 MPa and 25 J, respectively. The impact energy value was comparable to that of as-sintered 4% Ni sintered material, which is renowned for its high toughness.

To reduce the cost of powder metallurgy (PM) components, approaches such as increasing densities to enhance mechanical properties or using lower cost alloying elements to improve the cost performance ratio have been used.

Nickel, copper, and molybdenum have been the most common alloys used in PM. Nickel and copper are very efficient alloying elements, offering a good balance between properties and ease of utilization. However, PM is competing for nickel powders with the ever-growing battery market leading to price increases. Additionally, copper has been on the list of elements to replace for sustainability issues. Moreover, molybdenum is a very costly alloying element.

Ferrochromium is a lower cost alloy and is typically used in the prealloyed state, reducing possible segregation, and improving part-to-part stability. This paper will compare the performance of a low alloy chromium grade compared to common grades.

The high temperature deformation behavior of SUS316L austenitic stainless steel with a homogeneous and a harmonic structure (HS) was investigated by a compression test. The HS is a heterostructure having a coarse grain structure (Core) embedded in a fine grain network structure (Shell). In the tensile test at room temperature, the HS materials exhibit high strength with high ductility due to the hetero- deformation-induced (HDI) strengthening, i.e., enhanced strain hardening. However, the high temperature deformation behavior of HS and homogeneous specimens is not clear, especially under different strain rates. In the present study, the high temperature deformation behavior of the HS and homogeneous structure SUS316L stainless steel specimens was investigated from the activation energy point of view of the high temperature deformation. As a result, the activation energy mainly depends on the grain size of the specimens under high temperature deformation.

While Mn, Cr, and Si are widely used in ingot metallurgy, their use in the powder metallurgy (PM) industry is limited by their high affinity with O. In recent years, the use of these alloying elements in the form of master alloys (MA) has aroused interest due to their potential to substitute critical and widely used elements such as Cu or Ni for pressed and sintered automotive components. These alloying elements are aimed at providing sinterability and competitive mechanical properties to low-alloyed sintered steels. The MA route enables the effective introduction of these alloying elements during sintering while reducing their oxidation. This work studies the effect of C, Cr and Si content of three Mn-based master alloys on the as-sintered microstructure and mechanical properties of low-alloyed steels. The link between volume of liquid phase formed at sintering conditions and materials properties has been analysed.

WC-Co cemented carbides (alloys) sometimes exhibit shape distortion during sintering which cannot be explained by the inhomogeneity of the green density or the effect of self-weight. We investigated the shape distortion of WC-Co alloys during sintering focusing on the liquid phase migration (LPM) and the temperature gradients that arise within the sintered compact. In order to accurately capture the phenomenon, ground round bars were reheated under various conditions, and the distribution of Co content and diameter along the longitudinal direction was investigated in detail. As a result, we found that during cooling after sintering, an inevitable temperature gradient is generated in the round bars, and the LPM occurs from the high temperature region to the low temperature region, resulting in the shape distortion. The faster the cooling rate, the larger the distortion. It was also found that the liquid phase migrates from the Co liquid phase region toward the Co solid-liquid coexistence region. We have concluded that the LPM towards the solid-liquid coexistence region is caused by the migration pressure occurring in the region, which we have named Π_SL. Π_SL should be generated because F_WC/Co(S) derived from γ_WC/Co(S) and γ_Co(L)/Co(S) is higher than F_WC/Co(L) derived from γ_WC/Co(L).

WC-Co cemented carbides alloyed with Ru are relevant for the hardmetal industry in spite of their high cost. These alloys are used in applications requiring very demanding thermal properties and good performance in aggressive and abrasive media. For some applications, it is difficult to find an alternative material that could offer a similar performance. Ru containing binders (based on Co, Ni, CoNi and CoNiCr) are analyzed in this work considering carbon contents covering the whole carbon window, and using an equivalent WC-binder Ru-free alloy for comparison. The addition of Ru modifies significantly the chemical composition of the binder which can have important consequences in aspects such as phase formation and grain growth, and also in the final material properties.

The relation between transvers rupture strength, σ_m, and defect size, 2a, on the fracture origin on ultrafine-grained WC–10Co cemented carbides sintered in vacuum and hot isostatic pressed (HIPed) with the pressure of 1 and 100 MPa were investigated. The values of σ_m and 2a were obtained broadly by measuring for a lot of specimens as sintered and HIPed states. A clear correlation was provided on relations between σ_m and 2a on two type plots of σ_m vs (2a)^-1/2 and σ_m^-1 vs (2a)^1/2 and the relations were affected by WC grain size of the cemented carbides. Limiting strength on the plots of σ_m vs (2a)^-1/2 were confirmed clearly. The limiting strength seemed to be affected by not only mean WC grain size of specimen but also carbon content. It is suggested that limiting strength is affected by matrix strength.

WC-Co ultrafine cemented carbides added with Ti(C,N) particles of different sizes were fabricated by liquid-phase sintering. The microstructures of these alloys were investigated and compared with those of other carbides. Fine Ti(C,N) addition inhibited the growth of WC grains to almost the same level as Cr₃C₂ addition. The mechanism underlying the grain growth inhibition by Ti(C,N) particles was the pinning effect (Zener) of the second-phase particles, which was different from the reported mechanism of VC and Cr₃C₂ addition. Adding Cr₃C₂ to this alloy resulted in an extremely high strength with an average of 4.7 GPa and a maximum of 5.1 GPa, the world’s highest level. When applied to a cutting tool, these materials demonstrated excellent cutting life. Moreover, novel applications can be expected to take advantage of these properties.

The bending strength of ultrafine-grained cemented carbides exceeds that of normal-grained cemented carbides. This was thought to be due to the smaller size of defects within the ultrafine-grained cemented carbides. However, this had not been verified because the specimens broke up into numerous smaller pieces during bending tests. In addition, previous studies on the bending strength of normal-grained cemented carbides reported that there is limiting strength which is a region of not increasing bending strength by reducing the defect size. Therefore, in this study, with the aim of clarifying the cause, we conducted tensile test, in which many small pieces are expected to be unlikely to be generated, and additional tests such as bending test. The ratio of bending strength to tensile strength was comparable between the normal- and ultrafine-grained cemented carbides. The number of fragments produced at fracture was also similar between the normal- and ultrafine-grained cemented carbides when they had similar strength. These results indicated that there was no clear difference in the fracture phenomena of these two cemented carbides. It was clear that the tensile strength of both the normal- and ultrafine-grained cemented carbides increased as the size of the defects decreased and the limiting strength did not emerge. This finding encourages further strength enhancement of ultrafine-grained cemented carbides by controlling defects.

Cemented carbides of fine-grained WC-Co combined with VC has high hardness and strength for cutting tool. VC is known as a grain growth inhibitor; however, its effect on the microscopic mechanical properties, especially the WC-WC bonding strength, remains unclear. In this study, we investigated the WC-WC interfacial structure and the strength of WC-Co, WC-Ni and WC-VC-Co. Microcantilevers, including the WC-WC interface, were fabricated using mechanical polishing and focused ion beam (FIB) methods. Bending tests were performed using the nanoindentation technique to determine the WC-WC interfacial bonding strength. The results showed that the WC-VC-Co have lower strength than WC-Co. Transmission electron microscopy (TEM) observations indicated the segregation of V on the WC surface. The V-based thin layer reduces the strength between the WC grains, resulting in poor mechanical properties that induce WC-particle dropout. Hence, appropriately controlling the amount and size of VC is crucial for achieving good mechanical properties.

The economic and environmental considerations are increasingly compelling the hardmetal industry to reduce or even eliminate the use of traditional binder metals, such as nickel and cobalt. Fe-based alloys and steels have emerged as the most promising candidates for developing entirely Ni/Co-free hardmetals. While pure Fe is less effective as a binder phase, the austenitic FeMn and ferritic FeCr alloys show potential as competitive alternatives to standard well-established binders. This work examines the performance of alternative cemented carbides under abrasive-erosive wear conditions and compares them with conventional WC-Co hardmetals. Materials with different properties and microstructures are tested in high velocity erosive and impact-abrasion conditions. The focus is on the resulting wear rate and corresponding wear mechanisms. The findings suggest that, at comparable hardness levels, hardmetals with Fe-based binders can match or even exceed the wear resistance of traditional hardmetal compositions.

In the laser powder bed fusion (L-PBF) method, Ar gas flows to remove fumes and quenches the specimen surface during solidification. This rapid cooling induces solidification segregation and solidification cracking. Preheating, which relieves rapid cooling and decreases residual stress would be important. In the powder bed fusion EBM, preheating is commonly used to prevent smoke and charging. However, in the L-PBF method, using preheating is not always common. This work aims to clarify the thermal behavior during the L-PBF process using preheated base plate temperatures (200°C and 600°C) for the IN718 superalloy using COMSOL simulation and experiment. The creep properties and microstructure of IN718 were found to be influenced by the preheating temperature. The specimen preheated at 600°C exhibited longer creep life and elongation than the specimen preheated at 200°C because of a lower amount of Nb segregation in the specimen preheated at 600°C during the L-PBF process.

This study investigates the influence of build height variation and heat treatment on the microstructure evolution and tensile properties of IN718 alloy produced by Direct Energy Deposition (DED). Microstructural evolution and tensile properties were evaluated at room temperature and 650°C for samples taken from three build heights: 5 mm (bottom region), 21 mm (middle region), and 45 mm (top region) from the substrate. The microstructural observation indicate that the bottom and middle samples exhibit a higher fraction of γ′/γ″ phases and fine Laves/δ phases in the as-built condition due to in-situ heat treatment from repeated thermal cycles, leading to enhanced strength compared to the top sample, which primarily contains coarse Laves phases. Post-heat treatment (HSTA) leads to dissolution of the fine Laves/δ phases in the matrix, promoting recrystallization in the bottom sample and resulting in reduced tensile strength at both room temperature and 650°C compared to the top and middle samples. The tensile fracture mechanism of IN718 alloy involves fracture and debonding of the Laves phase, highlighting the inhomogeneous microstructures and corresponding mechanical property differences along the build direction. These findings emphasize the need for further research on post-heat treatment processes to optimize material performance.

Additive manufacturing (AM) technology has been experiencing high growth in recent years to produce a variety of metals and alloys. In such additive manufacturing, the storage condition of the powder affects the flowability of the powder and the microstructure and mechanical properties after the additive manufacturing process. In this study, in order to determine the difference depending on the humidity of the powder, STS 316L powder was dried at 60°C for 24 hours and then immediately subjected to the DED process. In addition, STS 316L powder was heat treated for 24 hours at 5%, 35%, 50% and 70% RH, respectively, and then DED. The process was carried out and classified into four conditions. Powder phase composition and morphology classified according to each condition were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM). The moisture content of the powder was also measured, and flowability was evaluated using Avalanche Energy and Cohesion-T values. The microstructure of the bulk material produced through the DED process was investigated through scanning electron microscopy (SEM).

In the powder bed fusion (PBF) type additive manufacturing (AM), understanding the relationship between the quality of the powder bed and the powder spreading process is crucial to avoiding defect formation. In this study, we investigated the powder-raking behavior during the multiple-layer fabrication process by discrete element method (DEM) and computational thermal-fluid dynamics (CtFD) simulations. The integrated PBF process simulation revealed that the gap height between the powder spreading blade and the build platform increases nonlinearly with the number of stacking layers, and accordingly, the powder-covered area ratio increases in the formed powder beds and affects the melt pool shapes. The powder raking behavior and melting and solidification behavior are related to each other, and both the powder raking and the irradiation conditions need to be optimized to obtain a high-quality part in the PBF process.

Al alloys possess excellent physical and mechanical properties, such as high strength and ductility. Recent research has actively applied additive manufacturing (AM) techniques using Al alloy powder for lightweight design to improve machine efficiency. However, the inherent physical properties of manufactured Al alloys by AM, including porosity, lack of fusion, and cracking, pose challenges in achieving defect-low additive manufacturing of high-strength Al alloys. The Al alloy powder characteristics, such as thermal conductivity and reflectance, impact the formation of defects of As-built Al alloy, like porosity and cracks, during the AM process. Controlling powder properties is therefore essential for preventing these flaws. In this study, the reflectivity, flowability, and particle size distribution of Al alloy powder produced by gas atomization were all comprehensively assessed. The microstructure and mechanical properties of the As-built Directed Energy Deposited Al alloy are subsequently analysed concerning the powder characteristics.

As one of the additive manufacturing processes, metal binder jetting enables the resource-efficient production of highly complex metal components and is more cost-effective for small batch sizes compared to metal injection molding. At the end of the metal binder jetting process chain, the components are sintered as well, whereby they are subject to a shrinkage of up to 20 %. To effectively address this issue, a precise understanding of the friction between the component and the setter plate is indispensable. This knowledge is important for gaining insights into the phenomenon and, notably, for refining the simulation of the sintering process. Therefore, this paper aims to contribute by introducing a custom-made setup for high-temperature tribometry of metal binder jetting components and presenting measurements of the coefficients of friction at room temperature as well as 1100 °C between samples printed in 17-4 PH and aluminum oxide plates of different porosity, roughness and states of use.

AM technology, in which metal or ceramic powders are laminated at high density and sintered and densified by powder metallurgy technology to form the final product, is attracting renewed attention in place of conventional Additive Manufacturing(AM) technology. In particular, inexpensive printers are available for the MEX (Material EXtrusion) using the FFF(Fused Filament Fabrication) method, and low-cost metal 3D printing can be easily realized by using the FFF equipment, and fabricate specimens using a filament made of metal powder and resin compounds. On the other hand, metallic materials with high porosity have been attracting in recent years. These materials are expected to have both light weight and strength, thermal insulation and sound absorption properties, and excellent impact force absorption properties. In this report, we investigate the fabrication process of porous materials using metal AM by the FFF method. In particular, we will attempt to fabricate stainless steel products with Kelvin’s_tetrakaidecahedron lattice structure by FFF method fabrication process and investigate the possibility of this process.

By oxidation-reduction treated to roughen its surface of W, combined with the infiltration method, to enhance bonding with W-10Cu. The effects of the oxidation temperature on the interfacial microstructure, mechanical property and thermal shock performance of W/W-10Cu joints were investigated. The results demonstrate that oxidation treatment notably enhances the microstructural quality and increases the contact area between W and W-10Cu, thereby strengthening the mechanical interlocking force. At an oxidation temperature of 900 °C, the joints achieve a maximum shear strength of 295.3 MPa. Moreover, the oxidation process effectively mitigates the expansion of cracks following thermal shock. Despite a general reduction in shear strength post thermal shock, joints treated with oxidation at 900 °C showed the least decline, maintaining a strength of 240.7 MPa. These findings substantiate the critical role of oxidation treatment in enhancing the performance of W/W-10Cu joints.

Mechanical metamaterials exhibit unique and novel mechanical properties through the rational design of their microstructures. Here, we strategically employ porous lattice structure designs to optimize mechanical properties along the loading direction, aiming to develop high-performance mechanical metamaterials. This study utilizes advanced nanoparticle jetting (NPJ) technology to fabricate porous zirconia ceramics with a micrometer to centimeter-scale lattice structures. By integrating modeling, NPJ 3D printing, and meticulous post-processing adjustments, we systematically produced porous zirconia with lattice structures exhibiting porosities of 60%, 70%, and 80%. Remarkably, the resulting compressive lattice structure demonstrates an exceptional specific strength of 426.94 MPa/(g/cm³). This research introduces an innovative approach to the design and fabrication of porous ceramics and demonstrates unprecedented controllability, providing valuable insights into the development of advanced lightweight, high-strength ceramic materials suitable for a range of engineering applications.

The press-and-sinter (PS) process often uses coarse powders, leading to low-density compacts and poor mechanical properties for 17-4PH. To improve these properties, fine 17-4PH powders, usually used in metal injection molding (MIM) process, were considered. However, fine powders pose challenges in the PS process due to their high friction, which leads to difficulties in molding. In this study, we used granulated 17-4PH MIM powders with excellent flowability for the PS process. We examined the effect of sintering temperature on the sintered density and mechanical properties of 17-4PH compacts. Results show that temperatures above 1260°C introduce the δ phase, enhancing diffusion rate, pore spheroidization, and grain refinement. Sintering at 1320°C in a H₂ atmosphere yielded parts with the highest density (7.4 g/cm³) and optimal mechanical properties. In contrast, temperatures above 1360°C caused uneven alloy distribution and grain coarsening, reducing performance. Our results show that the HPM process achieves mechanical properties comparable to those of MIM parts, while offering lower costs and shorter manufacturing times. This gives PM products a competitive edge in commercial applications.

Iron(III) oxyhydroxides such as goethite (α-FeOOH) and lepidocrocite (γ-FeOOH) can be prepared via the oxidation of iron salts such as iron(II) chloride (FeCl₂), iron(II) sulfate (FeSO₄) and iron(III) nitrate [Fe(NO₃)₃] in solution based on adjusting the pH using sodium hydroxide (NaOH). Lepidocrocite can act as a precursor for the generation of maghemite (γ-Fe₂O₃), which exhibits unique magnetic, electrical and pharmacological properties and thus has attracted significant attention. The present study prepared lepidocrocite, goethite and the spinel structure iron oxides maghemite and magnetite (Fe₃O₄) without controlling the pH of the reaction solution. Specifically, both lepidocrocite and goethite were precipitated by oxidizing iron(II) chloride in solutions containing calcite (CaCO₃) under air. The extent to which goethite was produced increased with increases in the calcite concentration. Spinel structure iron oxide particles with 50 nm in size were also obtained by oxidation of the same solutions under N₂.

In this paper, the effects of two manufacturing techniques on the microstructure and mechanical properties of Ni-based superalloy disks ware examined. The study focuses on FGH4097 superalloy, the bars were powdered using SS-PRER^® technology and subsequently canned for processing via hot isostatic pressing (HIP) and HIP + isothermal forging methods. After each processing stage, the components underwent standard heat treatment (HT) as well as HT with solution at bellow γ′-solvus temperature.The tensile, creep, and stress rupture properties were evaluated to provide an understanding of the alloys′ structural behaviour following each processing step. The grain was refined resulting in room temperature tensile strength exceeded 1620 MPa. Interestingly, the creep strain of only 0.05% for 100h of creep at 700°C/500 MPa.

Gadolinium has a neutron absorption capacity approximately 67 times higher than boron. However, because of its poor solubility in the Fe-Cr matrix, Gd tends to form brittle intermetallic phases, which significantly reduces ductility and corrosion resistance. To retrieve this problem, Gd2O3 employed as functional phase, because oxides are extremely stable and effectively inhibit the formation of undesirable phases. Furthermore, uniformly distributed oxide particles can play a role as strengthening phase and this is one of the promising methods to enhance mechanical properties at elevated temperatures. In this study, fine Gd2O3-dispersed stainless steels were fabricated by mechanical alloying, hot isotactic pressing processes. Thin sheets were successfully fabricated with cold rolling and intermediate heat treatment. And then, microstructures and tensile properties were systematically investigated. Experimental results suggest the potentiality of ODS stainless steels for neutron-absorbing structural materials with favourable neutron absorption capacity, mechanical properties and corrosion resistance.

Boron carbide materials exhibit excellent mechanical properties such as high hardness and wear resistance. However, boron carbides are difficult to sinter, especially in boron-rich regions, because of the low self-diffusion coefficient caused by the strong covalent bonding of boron. To improve the sinterability of boron carbides,we disscussed the sintering conditions. we applied Reaction Boronizing Sintering (RBS), using an eutectic reaction between boron and 3d transition metals to the synthesis and SPS consolidation and promote the densification of boron carbide base materials. Boron carbide materials were prepared by powder metallurgy using the spark plasma sintering method from amorphous boron powder, carbon powder, and metal powders, such as Co and Ni. The Densification of the boron carbide materials was promoted by the metal addition, while the microstructure of the spark-sintered samples was largely different.

Transition metal diborides with an AlB₂-type structure exhibit excellent mechanical properties, wear resistance, and high temperature stability. For example, TiB₂ has excellent mechanical and wear resistance properties. However, the preparation of pure, dense, sintered transition metal diborides is difficult, as high temperatures, high pressure, and sintering aids are required in the sintering process. In this study, we applied spark plasma sintering (SPS), a powder metallurgy technique that enables rapid sintering via Joule heat generated by an electric current. We fabricated (Ti, M)B₂ diboride solid solutions (M = V, Mo, W, etc.) by means of SPS. The X-ray diffraction results verified the AlB₂-type structure of the prepared (Ti, M)B₂ solid solutions.

As the industrial and scientific communities embrace sustainable manufacturing and resource-efficient consumption, replacing traditional cobalt and nickel-based binders, along with tungsten carbide-based hardmetals, becomes essential. This study examines the impact of sintering temperature on the microstructural evolution and phase transformations of “green”, high-chromium content, iron-bonded Titanium Carbonitride (Ti(C,N)-FeCr) cermets. Comprising 70wt.% Ti(C,N), Fe, and 26 binder wt.% Cr, the cermet was sintered in a vacuum furnace. A clear connection was established between the microstructural evolution, mechanical properties, and wetting behavior of the cermet. Scanning electron microscopy (SEM) and optical microscopy (OM) revealed improvements in grain shapes, binder distribution, and dihedral angles with increasing sintering temperature. However, mechanical properties peaked at an optimal temperature of 1550°C. X-ray diffraction (XRD) confirmed the formation of M7C3 carbides, Ti(C,N), and FeCr phases, validating the phase diagram calculations. Enhanced wettability of FeCr bonded Ti(C,N) cermet was also demonstrated.

The compression rheological behavior of Mo-12Si-8.5B alloy reinforced by layered Mo₂TiAlC₂ phase is studied at temperatures ranging from 1200℃ to 1400℃ and strain rates ranging from 0.01s^-1 to 0.0001s^-1. The trend of flow stress and microstructure evolution was investigated. The results show that the Mo₂TiAlC₂ strengthens the Mo-12Si-8.5B alloy mainly by particle strengthening and grain boundary strengthening at high temperatures, with the increase of Mo₂TiAlC₂ content, the peak stress of alloy improved by 43.8% at most. With the increase of test temperature or the decrease of strain rate, the peak stress of alloys decreases significantly. The microstructural observations reveal that the deformation of Mo-12Si-8.5B-Mo₂TiAlC₂ alloy at high temperatures is mainly provided by the plastic deformation of the soft α-Mo phase and grain boundary sliding. As the temperature rises to 1300℃-1400℃, the intermetallic phase gradually participates in the deforming, however, it contributes less to the total deformation, while dynamic recovery and recrystallization greatly reduce dislocations, and the deformed α-Mo grains are re-equiaxed. The Mo₂TiAlC₂ particles can inhibit dynamic recrystallization grain growth to some extent.

FeB-Ni hard materials demonstrate high hardness, excellent wear resistance and cost-effectiveness, establishing them as promising candidates for novel hard materials. To enhance its application as cutting materials, it is crucial to further improve its hardness and fracture toughness. In this study, the performance of FeB-10Ni hard materials were enhanced through the addition of Al. The alterations in the microstructure and phase composition of the sintered compacts with varying Al contents were analyzed. Additionally, the hardness, fracture toughness and density of the sintered compacts were evaluated. FeB-10Ni-Al hard materials were prepared by ball milling and spark plasma sintering (SPS). The powder compositions exhibit Al contents varying from 1 to 10 vol.%. The results showed that FeB-10Ni-Al hard materials with different Al contents were successfully synthesized under the following conditions: ball milling for 21.6 ks, sintering at 1373 K, holding for 0.9 ks, and applying a pressure of 50 MPa. With the Al contents increased, newly NiAl phase emerged in the sintered compacts, significantly enhancing both hardness and fracture toughness. In general, compared with FeB-10Ni hard materials, the hardness and fracture toughness of FeB-10Ni-4Al increased by approximately 33% and 64% respectively, while its relative density improved by about 3%.

Ti₃SiC₂-based composites prepared with elemental powders exhibit advantages such as thermodynamic stability and high bonding strength. In ternary systems, thermodynamic data, including the phase equilibrium relationships of the system, provide essential information for determining the reaction mechanisms and final products. The equilibrium phase diagram of the Ti-Si-C ternary system and the existing thermodynamic data estimated unknown thermodynamic properties and calculated the chemical potential of each component. The composite was prepared by spark plasma sintering (SPS) of Ti, Si, and C elemental powders through in-situ reaction at 1573 K. Based on the microstructural observation and XRD results of the composite, the phase formation mechanism and reaction path of the in-situ reaction of three elemental powders in the Ti-Si-C system were analyzed.

TiB₂ is challenging to sinter to high density due to its low self-diffusion coefficient and high melting point. Typically, metals are used as a binder phase to lower the sintering temperature. In previous research, metal-TiB₂ composites were prepared using the SPS sintering method at temperatures exceeding 1500°C. In this study, TiB₂ powders of 3μm (denoted as S-TiB₂) and 63μm (denoted as L-TiB₂) were utilized. The powders were mixed in proportions where L-TiB₂ constituted 0%, 25%, 50%, 75%, and 100% of the total TiB₂ mass. TiB₂-10Ni composites were then prepared by the SPS sintering method at 1100°C under a pressure of 50 MPa. At this temperature, TiB₂ grains did not grow, and the composites contained only TiB₂ and Ni phases. where the hardness of the composites with 25% of L-TiB₂ can reach 2122 HV, while the relative density of the composites with 50% of L-TiB₂ exhibited a hardness of 1904 HV, while the composite with 50% L-TiB₂ achieved a relative density of 99.6%. Observations indicated that the composites with 25% and 50% L-TiB₂ had smaller Ni-rich areas. The L-TiB₂ particles adsorbed a portion of the Ni, inhibiting its aggregation, which in turn improved the density and hardness of the composites.

By performing a dilatometer experiment, measured shrinkage can be used to determine the adjustable parameters in a constitutive model for sintering. While the dilatometer machine is excellent at collecting data, its conditions differ from those in an industrial sintering oven. Therefore, the constitutive model must be robust and in the present study, different sintering time cycles have been used to optimize the adjustable parameters in the model. Investigations on initial density has also been performed to better understand the sintering process. Before sintering of particles begins, during the debinding process, densification can be detected, which is dependent on the initial density. The constitutive model for sintering was improved to include this phenomenon by adding particle rearrangement based on the theoretical packing of spheres.

Effects of WC grain size, Co content and Cr₃C₂ addition of WC-Co based cemented carbides on tensile fatigue property were investigated because tensile repetitive stress often causes fracture of impact punches. To determine loads of repetitive stress for measuring fatigue property, tensile strength of each cemented carbide was measured. Fatigue property was evaluated by number of times of repetitive stress until fatigue fracture of the cemented carbides for several repetitive stress at each grade of cemented carbide. The specimens were broken into two in a small number of times for high repetitive stress. The specimens were not broken until numbers of times of 10⁷ by decreasing the repetitive stress to 30-50 % of the tensile strength. Fining grain size of WC, optimized Co content and adopting Cr₃C₂ increased number of times for a same repetitive stress.

Mo₂NiB₂-Ni cermets have been sintered using “Reaction Boronising Sintering (RBS)” proposed by K. Takagi. In RBS, the generation of an inhomogeneous microstructure of the boride phase occurs. In this study, the calcination and mechanical milling processes were introduced into the sintering process of Mo₂NiB₂-Ni cermets to separate the phase formation and densification and refine the microstructure. According to SEM observations, the porosity and grain size was reduced after calcination. It was also found that cermets with higher transverse rupture strength (TRS) and hardness were obtained. In addition, changes in the sintering process resulted in lower optimum sintering temperatures for obtaining these properties.

Mo₂NiB₂-Ni cermets, one of the boride-base cermet, have been investigated as an alternative material to WC cemented carbides. By adding Cr and V to the Mo₂NiB₂-Ni cermet, the crystal structure of the Mo₂NiB₂ is changed from orthorhombic type to tetragonal type, and mechanical properties show enhancement. However, details of structure deformation and the mechanical properties of Mo₂NiB₂ phases still need to be discovered. In this study, we performed a nano indentation measurement to investigate the hardness of the Mo₂NiB₂ phases. Cr and V doped complex boride base cermets with tetragonal structure-type and non-doped Mo₂NiB₂-Ni cermet with orthorhombic type structure were sintered using Reaction Boronising Sintering method proposed K. Takagi. According to the nano-indentation measurement, the hardness of the tetragonal phase exhibited 25 - 28 GPa, while that of the orthorhombic phase showed 20 - 23 GPa.

Bluish glass was successfully prepared by mixing oxides and carbon as a reductant into the starting materials, whereas the addition of only α-Fe₂O₃ into the glass raw materials provided greenish glass. The chemical state of the iron ions in the glass was likely modified from Fe³⁺ to Fe²⁺ by the reducing atmosphere caused by carbon during the heating process. Mössbauer spectra and spectrophotometric measurements indicated that the bluish glass contained a high proportion of Fe²⁺ (67.4%) and mainly absorbed visible light with wavelengths longer than 500 nm.

Traditionally, Japanese Bizen stoneware is produced by firing shaped green clay in a firewood kiln at approximately 1200 °C using red pine as fuel. In some cases, an ocher coloration known as goma appears on the finished product due to reactions between the clay and firewood ash. This work shows that goma results from the formation of augite [(Ca,Mg,Fe)₂Si₂O₆], plagioclase [(Ca,Na) (Si,Al)₄O₈] and glassy phases. Bizen ceramicware exhibiting goma was fabricated by heating a mixture of Bizen clay with an artificial ash based on the analysis of red pine ash and produced using chemical reagents. An ocher coloration appeared on the sample surface after heating a 70:30 (on a mass basis) mixture of clay with this artificial ash at 1220 °C for 5 h followed by annealing at 1100 °C for 2 h in an electric furnace.

There have been urgent needs to develop advanced technologies for sustainable energy systems due to the rapid development of global society. Evaporation-driven energy generation system is emerging renewable energy technology motivated from the natural phenomenon in the plants’ stomata i.e., water evaporation from root to leaf. This research has attempted to develop novel evaporation-driven energy harvesting device based on the electrospun nanofiber with carbon black powders. Notably, carbon block powder plays important roles to increase the hydrophilic properties, higher level of porosity as well as conductivity of the generation device. These characteristics could finally support to accelerate the generation output as well as the vapor permeability of the elecrtospun nanofiber mat. The result of this research highlighted that applying carbon black powders to the electrospun nanofiber mat (20.0×40.0×0.9 mm³) brought the maximum voltage and current of ~ 0.21 V and ~ 0.12 mA, respectively.

Gas atomization of recycled Inconel 713LC (IN713LC) casting scrap was studied to produce feedstock powders for laser additive manufacturing. Nickel-based alloy powders and the laser metal deposition (LMD) process are used to remanufacture IN713LC castings to repair casting defects and improve the yield of castings. The material characteristics of nickel-based alloy powder and the microstructure of LMD castings were investigated. The effect of aging treatment on the microstructure and hardness of the repaired area is also discussed. The experimental results show that IN713LC alloy powders of 50~120 μm are suitable for LMD coating at 500-700W laser power. The fine microstructure of LMD layer is a mixed structure with both columnar and equiaxed grains. There is a good interface between the LMD layer and the casting substrate, no voids or cracks were observed. After aging treatment, fine γ’ precipitates are precipitated in the austenite matrix of the LMD layer, so its microhardness can be increased to more than 387 Hv.

Mo-Ni-Ti alloy sputtering target samples were prepared using Mo powder and Ni-Ti alloy powder as raw materials by hot isostatic pressing. Density, phase composition, microstructure and element distribution of Mo-Ni-Ti sputtered target samples were measured by OM, SEM and EDS. The experimental results show that hot isostatic pressing can prepare large-sized Mo alloy target at lower temperature, and the obtained samples have finer grains, higher density and more uniform element distribution than that of non-pressure sintering. In this work, Mo-Ni-Ti sputtering targets (Purity>99.95%, density>99.5%, particle size<100 μm, component deviation<0.5 wt%) were obtained by hot isostatic pressing.

Hot Isostatic Pressing has been used to consolidate components for the power generation industry for many years, and with the renaissance of nuclear fission and fusion interest, HIP (HOT ISOSTATIC PRESSING) will play a significant role. This presentation will focus on powder metallurgy-based production of critical components in the power generation sector. Latest developments in the development of World record HIP equipment will also be discussed.Keywords: Hot Isostatic Pressing, Heat Treatment, Powder Metallurgy, Near Net Shape, Energy Sector