The objective of this experimental investigation is to identify the effect of powder characteristics and printing parameters on the green density of BJT part. The study conducted has evaluated the powders with INDO-MIM engineered Particle size distribution (PSD) (D100: -60 microns), Standard AM powder PSD (D100: -25 microns) with varying particle size distributions with varied layer thickness and binder saturation. The tailor-made PSD shows a significant increase in flowability. The results show that by optimizing the particle size distribution increases the green density and helps to increase the layer thickness up to 80μm. In Standard AM powder the green density was found decreasing with increasing layer thickness, A high layer thickness led to delamination on the surface after spreading a new layer on a printed layer. In tailor made powder layer thickness increased double compared to standard AM powder with good printability and without defects. The tailor-made powder sintering shrinkage is reduced 10-11 % with ~ 99% sintered density, good mechanical properties, good dimensional consistency with high productivity.

Metal binder jet (BJT) 3D printing is suitable for fabricating metal parts in small to medium quantities and many varieties in a short period. Fine powders for metal injection molding (MIM) are used for binder jet 3D printers. In this study, powder characteristics for binder jet 3D printing are focused while comparing it to metal injection molding process. The effect of powder loading in the green compacts on debinding and sintering behavior is investigated. The green densities of the specimen fabricated by several processes were changed by powder loading, and it is clarified that the sintered density was determined by green density.

This study aims at presenting the current status of the IN718 development using Binder Jetting at Safran and the challenges associated with its industrialization for aeronautic applications.Printing tests done on several laboratory/production machines, with powders from different suppliers and with various particle size distributions will be used to exemplify the impact of such parameters on the part quality at each stage, from printing to sintering. A study of part density, sintering, reproducibility has been performed as well. Based on these findings, a map of influent parameters will be shared to elucidate the path towards industrialization and certification of parts in the aeronautic field. Perspectives will be given regarding the common framework to be developed for the Binder Jetting to become the cost efficient and high material quality process.

Powder in sinter-based metal binder jetting is not fused but only bonded, which in principle ensures full reusability of the unbonded powder. This increases both resource and cost efficiency. In order to explore this potential, this study investigates the effect of powder recycling with regard to handling and thermal influences. For this purpose, a gas atomized Ti-6Al-4V powder is used as a reference powder. It is shown that recycling the Ti-6Al-4V powder four times leads to a minor change in the particle size distribution and an improvement in flow properties. No differences in the average green part densities could be determined, but an increase in their range (from 1 to up to 7 %). Furthermore, it is demonstrated that the thermal influence due to curing and conditioning (temperatures ≤ 200°C) after printing does not lead to a significant increase in oxygen or nitrogen even after 15 repetitions.

Metal binder jetting (MBJ) offers great opportunities for fabricating high-strength titanium alloys for aerospace, medicine, and industrial applications. In this work, we studied the effect of particle size and surface energy on the dynamics of binder spreading and imbibition in Ti6Al4V powder beds by employing high-speed camera imaging and the Wilhelmy method. It is shown that binder imbibition in the titanium powder bed is significantly changed with the particle size due to geometrical-medicated wettability, capillary forces, and the surface oxide layers. Moreover, it is demonstrated that atmospheric pressure plasma processing of the powder particles can be used to modify the surface energy of particles, enhancing wettability. X-ray photoelectron spectroscopy shows that plasma treatment in nitrogen changes the type of surface oxide, thus improving the imbibition rate by an order of magnitude and the saturation rate by about 30%. The equilibrium saturation is also increased by about 15% Our results introduce a new strategy to enhance the processability of titanium powder for MBJ.

Binder Jetting (BJT) of gears is a multi-stage additive manufacturing (AM) process that generates part geometry by depositing a liquid binder in a powder bed layerwise. The BJT process produces green compacts of gears that are sintered by secondary heat treatment processes. The impact of various process parameters on the reproducible manufacturing of gears has not been systematically investigated. The selection of process parameters, such as printing speed and binder volume, is often an iterative process based on the knowledge of both the user and machine manufacturer. Previous studies have primarily focused on binder application phenomena and do not provide validation for the mentioned process parameters for gear manufacturing. This report presents a systematic method for validating the printing speed and binder quantity in terms of reliability, productivity, and economy for manufacturing BJT gears. The knowledge gained allows for the determination of optimal process parameters based on experimental data.

Due to near netshape production, additive manufactured gears have a high potential to optimize cost and resource efficiency. Decreasing product lifecycles as well as increasing individualization of components demand high flexibility of manufacturing processes. The additive manufacturing process Binder Jetting (BJT) is intended to enable the production of individualized gears in small batch sizes. The gears meet all requirements regarding quality, strength, acoustics and cost-effectiveness. This report initially classifies the tooth bending strength results of 17-4PH BJT gears in comparison to conventionally cut gears. In addition, rotary bending specimens are manufactured (additively and conventionally) in order to derive a possible analogy of the bending stress to the nominal tooth root stress. The specimens may provide an economical alternative for the process design of BJT gears. A full SN-curve is derived for both, gears and rotary bending specimens. The knowledge gained significantly optimizes the process design for BJT gears.

Metal binder jetting (MBJ) may enable customized mass production over other additive manufacturing technologies because of its unprecedented build rate and supportlessness unlike laser powder bed fusion. This technology is analogous to metal injection molding (MIM) except for a green-part-making process. It has advantages of creating more complex functional geometries with the help of lattices in components over MIM. In general, lattices in green parts are successfully build-up. Structural integrity problems may arise during sintering by experiencing unexpected distortion while shrinking and deforming. Here, we studied several lattices for load-bearing applications with the considerations of depowdering efficiency and sinter deformation. Consequently, we analyzed sinter-deformation characteristics for several lattice designs with simulations and experiments, and optimized their designs by measuring geometric and dimensional tolerances. We anticipate that this study will contribute to creating design guidelines for MBJ.

Binder jetting (BJT), an additive manufacturing process, injects a binder into the powder bed to build up the green body. The green body undergoes sintering to obtain a dense product. However, the shrinkage during sintering makes it difficult to achieve a high dimensional accuracy. Pressure-less melt infiltration (PMI) is an alternative process that fills the pores of a preform with a metal melt spontaneously infiltrating by the capillary force. It becomes important to clarify how molten metal infiltrates and how defects form. This study investigates the mechanism of defect forming inside PMIed Mg/Ti composites by controlling the structure of Ti powder preforms. Different-sized (20-2300 m) Ti powders were pressed under various pressures (76-153 MPa) to fabricate preforms with various structures. It was found that gravity and gas pressure were key resistant forces for the capillary infiltration.

This work emphasizes the evaluation of Binder Jet 3D Printed (BJT) M2 Tool Steel against the Wrought M2, Powder Metallurgy (PM) M2 and Laser Powder Bed Fusion (LPBF) Maraging Steel 13Ni400 for Mould Application.

3D printed mold with conformal cooled (CC) channels is one of the solutions to enhance part quality and productivity and to minimize manufacturing cost compared to the molds with conventional cooling channels. LBPF process is used to manufacture CC molds using maraging steel family alloys. The limitation in hardness (52 – 56 HRC) of maraging steels demands new material with high hardness (> 60 HRC) to improve life of the CC molds. High speed steels (HSS) are the alternative options, but LBPF technology is not well suited for high-carbon alloys. BJT is capable of handling high-carbon alloys, additionally, it offers equiaxed grains with isotropic properties and no supports required during BJT printing. M2 High-Speed Steel is known for well-balanced red hardness, wear resistance, and toughness. It is used in tempered condition with a hardness range of 58-65 HRC.

The standard M2 chemistry is not good enough for high hardness (> 60 HRC) and wear resistance which is essential for long tool life. Availability of customized metal powders for high-performance through BJT is possible. M2 metal powder properties optimization (chemical composition, particle size, and shape) is done to achieve a better performance in the BJT process.

The study shows that on friction properties, BJT M2 & Maraging steel 13Ni400 properties are almost same. But in wear resistance, BJT M2 exhibits superior properties compared to Maraging steel 13Ni400, Wrought M2 and PM M2 steels.

Improved hardness from modified chemistry and fine grain size due to optimized sintering process helped in achieving high wear resistance properties in BJT M2 material. Thus, BJT AM process is capable of handling high-carbon alloys without any concerns.

The Particle size, shape and chemistry played important role in improving the performance of BJT components. High-performance conformal cooling molds resulted in superior product quality with improved productivity.

The ColdMetalFusion process is a sinter-based metal Additive Manufacturing technology which aims to enable part fabrication in production quantities. The individual process steps are identical to Metal Injection Molding (MIM): green part formation, debinding and sintering. In contrast to MIM however, the material is a powdery feedstock developed, which can be processed on standard plastic selective laser sintering (SLS) systems. As the process chain is similar to MIM, the mechanical properties are also fully comparable.Due to the high stability of the green parts, the surface can be post-processed in green part state before sintering. Standard processes like grinding, blasting and machining can be used, which saves time and cost. Surface roughness of Ra of 1 µm and below can be achieved by cost-efficient post-processing methods. As the formidable component is the polymer binder, the effectiveness, duration and wear are independent of the metal.

In this study, through electron-beam powder bed fusion additive manufacturing, we prepared Co–27Cr–6Mo (wt.%) alloys with different C concentrations up to the eutectic composition (~2.5 wt.%). The Rockwell hardness of the as-built alloy specimens increased linearly with an increase in the carbon concentration, reaching approximately 60 HRC at 2.5 wt.% C. The as-built 2.5C alloy contained a fine carbide network consisting of M₇C₃- and M₂₃C₆-type carbide phases. Increasing the carbon concentration not only increased the carbide fraction and changed the carbide phases but also altered the solidification behavior from cellular at low carbon concentrations to dendritic and finally to eutectic. Quantitative X-ray tomography revealed that carbon addition also affected the gas pore behavior in the melt pool, significantly reducing the porosity when a flat solid/liquid front existed upon solidification (i.e., planar and eutectic). The developed high-carbon alloys cannot be obtained through conventional metal processing; hence, this study opens new avenues for industrial applications of additive manufacturing.

The range of martensitic Cr steels that can currently be processed with PBF-LB/M is considerably limited. In order to expand and optimize the alloy portfolio of this alloy category, the qualification of a corrosion resistant martensitic Cr-steel with good processability for additive manufacturing is the focus of this study. The study covers the entire process chain from alloy development based on X50CrMoV15 steel, powder production via gas atomization, additive manufacturing using PBF-LB/M and microstructural investigations. Nitrogen is the key element in this concept as it can have a positive effect on strength, ductility and corrosion resistance and environmental footprint. In addition, N improves susceptibility to cold cracking in melt based additive manufacturing processes by reducing the M_S temperature.

C-bearing tool steels with optimum combination of strength, toughness, wear, and tempering resistance show limited weldability, and processability by laser-based additive manufacturing (AM) processing, such as laser powder bed fusion (L-PBF). Because of this, highly alloyed Co-containing ultrahigh-strength maraging steels with excellent weldability re-emerged as commercialized alternatives for the use in AM, years after their prime in 1970-90s. However, cobalt in maraging steel becomes an obstacle in driving the shift towards sustainability. Lower thermal conductivity, wear damage, and in some cases, inferior thermal fatigue behavior are among other limitations of maraging steels. We report on the use of cost, and time-efficient computational alloy design in developing customized alloy powders to overcome these obstacles in view of the application-specific requirements. Microstructure, properties, and performance of Co-free Fe-Ni maraging systems, Co-containing Fe-Ni-C martensite with improved wear resistance, and Co free C-bearing hot work tool steel tailored for enhanced processability by L-PBF are presented and discussed.

Selective laser melting (SLM) is the dominant additive manufacturing (AM) process of metallic materials to date. The objective of this study was to investigate the effects of heat treatment on the microstructure and tensile properties of SLM Dievar Cr-Mo-V alloyed hot work tool steel. The three-stage heat treatment used in this study was austenitization followed by two tempering processes. The microstructure was analyzed by scanning electron microscopy, X-ray diffractometry, electron backscatter diffraction, and energy dispersive spectrometry. The results showed that the hardness, yield strength (YS), ultimate tensile strength (UTS), and tensile elongation of the as-built steel were 505 HV, 1123 MPa, 1748 MPa, and 11.7 %, respectively. The hardness, YS, UTS, and tensile elongation of the heat-treated steel were respectively 471 HV, 1517 MPa, 1598 MPa, and 13.0 %. The heat treatment obviously increased the YS but decreased the hardness and UTS. The correlations among the heat treatment, microstructure, and tensile properties are discussed in this study.

The neutron irradiation-induced increase in ductile-to-brittle transition temperature (DBTT) restricts the operational life of nuclear power plants. This study explores the potential of additive manufacturing technology to address this challenge. Using powder bed fusion (PBF), we produced a sample of SA508 Gr.3, a reactor pressure vessel material, and compared its mechanical properties with a conventionally manufactured sample. The PBF-printed sample exhibited a remarkable 114% increase in yield strength and a 58.3% increase in ultimate tensile strength compared to the conventionally made sample. Furthermore, the DBTT of the PBF-printed sample decreased by over 50 K compared to its conventionally made counterpart. These findings highlight the significant improvements in mechanical strength and DBTT achievable through additive manufacturing, demonstrating its feasibility for manufacturing reactor pressure vessels. This approach holds promise for extending the operational life of nuclear power plants.

3D-fabrication conditions of high sphericity SUS630 water atomized powders by using the Laser-Powder-Bed-Fusion (L-PBF) have been studied. Water atomized powders were characterized by particle size distributions, particle circularities and dynamic shear stresses of fluidity as compared with those of gas atomized powders. High-density SUS630 L-PBF samples up to about 99.0 % could be formed by using the water atomized powders under almost same 3D-fabrication conditions of the gas atomized powders.

Gas-atomized powder is commonly used for Laser powder bed fusion (L-PBF) additive manufacturing (AM) because of its good flowability. On the other hand, water-atomized powder is inexpensive and has great potential for application to middle range AM products. In this study, SUS316L water-atomized powder was applied to L-PBF additive manufacturing. Firstly, the relationship between particle size distribution and powder flowability was experimentally clarified that required for L-PBF additive manufacturing. Additionally, Mechanical properties of AM products with water-atomized powder were shown to be at level of industrial materials through evaluation of AM test pieces. Finally, an extruder die plate was manufactured based on the evaluated mechanical properties. It was revealed that water-atomized powder is useful for practical L-PBF AM products.

Oxide Dispersion Strengthened (ODS) superalloys are high-temperature alloys with enhanced mechanical properties at elevated temperatures. This is achieved by precipitating thermally stable fine oxides (such as Y₂O₃, ThO₂) or carbides within the metal matrix¹⁾. These alloys are primarily used in the field of superalloys and recently, the principle has been applied to various metals, including aluminum and copper alloys.

The ODS superalloys are generally manufactured by methods such as Hot Isostatic Pressing (HIP) and Spark Plasma Sintering (SPS) after mechanical alloy. These alloys have high strength, making it difficult to process complex shapes, and research on AM technology is being conducted as an alternative manufacturing method. In this study, the experiment was conducted with a Laser Powder bed fusion process using metal powder materials.

In this research, the ODS Ni-superalloy powder similar to the composition of MA6000 was manufactured using a gas atomization process. A specimen of the produced ODS Ni-superalloy powder was prepared by an L-PBF process. We measured changes in densification behavior of specimens according to L-PBF process parameters and conducted residual stress measurements in order to identify issues arising during the processing steps. Additionally, we analyzed the powder and PBFed specimens of ODS Ni-Super alloy using optical microscopy, scanning electron microscopy, XRD, and LPS analysis.

The demand for composite materials with heightened mechanical strength at elevated temperatures has driven interest in their development. This study employs laser powder directed energy deposition (LPDED) to examine the mechanical properties of Inconel 718 composite powders with varying TiCp concentrations at both room and high temperatures. During LPDED, TiCp dissolves into the matrix, forming (Nb, Ti)Cp and altering solidification characteristics. (Nb, Ti)Cp not only prevents Laves phase formation during LPDED but also effectively inhibits grain growth in subsequent heat treatment. Additionally, dissolved carbon atoms impede dislocation mobility, significantly impacting mechanical properties. This investigation underscores the intricate transformations achievable through precise TiCp control in LPDED, offering valuable insights into the development of high-performance metal matrix composites for high-temperature applications.

Additive manufacturing (AM) technology, commonly known as 3D printing, has been recognized as a transformative method in industries as diverse as automotive, medical, defense, power generation, aerospace, shipbuilding, and heavy equipment. Evolving from prototyping to mass production, AM is now being utilized to manufacture complex and precise metal components that require intricate geometries. The current study systematically explores key L-PBF parameters, including laser power, scan speed, and layer thickness to understand their impact on the microstructure and mechanical behavior of the resulting nickel-based superalloy IN718components. Through a comprehensive analysis of the fabrication process, we aim to identify the optimal parameter set that ensures the desired mechanical properties, including tensile strength, hardness, and fatigue resistance.

Additionally, the study employs advanced characterization techniques such as microscopy and mechanical testing to assess the performance of the material under different conditions. The findings presented in this research provide valuable insights for enhancing the reliability and efficiency of L-PBF-produced IN718 components in aerospace, automotive, and other high-demand applications.

Pores in cast, compacted or AM built material that shrink during HIP, can regrow if they are filled with argon and are subjected to high temperature. To better understand this, we present a study on a set of capsules that contain a huge 2 cm³ cavity (which in terms of volume is 10⁹ bigger than a typical AM gas pore). These cavities were filled with argon by sealing them under 1 atm of 100% argon. Using HIP these cavities shrink to an approximate size of 0.01 cm³ resulting in a room temperature pressure of ~206 bars. Upon stepwise reheating the pressure increases, and for IN718 the cavity expands above 900 °C (pressure is here ~824 bar), while for 316L the cavity expands above 1000 °C (pressure is here ~895 bar). The temperature at which expansion occurs are not far from typical HIP conditions, which makes sense.

Low build speed is a challenge for wider industrial adoption of Powder Bed Fusion – Laser Beam (PBF-LB) as it is directly associated with higher production costs. The build speed can be efficiently increased by increasing processing parameters i.e. layer thickness, scan speed and hatch distance. However, higher build speeds come at the cost of increased porosity and surface roughness. This study investigates the impact of higher build speeds on pore characteristics by increasing layer thickness from 20 to 80 μm and hatch distance between 100 to 250 μm. Detailed pore characterization by light optical microscopy combined with image analysis and Synchrotron X-ray Computed Tomography (SXCT) on selected samples indicated that pore distribution and characteristics can be tailored by change in the process parameters. Highly anisotropic pore orientation and distribution could be achieved via control of hatch distance, scan speed and layer thickness, providing the possibility of engineered mechanical strength in certain orientation.

A new class of CoNi-based high entropy superalloy (CoNi-HESA) was developed for laser powder bed fusion (L-PBF) additive manufacturing, integrating high entropy alloy (HEA) thermodynamics. The alloy (Co-35Ni-8Al-4Ti-4V-2W-2Ta-9Cr) was methodically crafted using gas atomization. Employing L-PBF, a comprehensive Design of Experiment (DoE) approach studied the impact of processing parameters (laser power and scan speed), establishing a process window for >99.9% relative density. Advanced electron microscopy revealed a single-phase fcc solid solution, confirming thermodynamic predictions. In parallel, the CoNi-HESA, designed for demanding applications in energy, space, and nuclear sectors, showcased impressive tensile strength (>1GPa), ductility (≈30%), and sustained yield strength up to 800°C. The alloy's crack-resistant properties make it ideal for L-PBF, revolutionizing high strength and temperature component production. CALPHAD calculations based on the HEA database validated the alloy design strategies. This study converges HESA synthesis, L-PBF optimization, and alloy performance, offering a paradigm shift in advanced manufacturing.

High Entropy Alloys (HEAs), a novel class of materials diverging from conventional alloying concept of single principal element, show immense potential, especially in high-temperature applications. This study leverages Laser Powder Bed Fusion (PBF-LB/M) to manufacture a CoCrFeNi-based HEA alloyed with minor additions of Mo and Nb using commercial powders like Ni-base superalloys and 316L in a cost-effective approach. The as-printed compositions resulted in alloys with single-phase FCC upon printing. Tensile tests at 700°C, 800°C, and 900°C reveal enhanced strength compared to similar alloys in the literature, facilitated by Mo and Nb-rich precipitates. This work not only advances understanding of HEAs but also offers insights for future alloy design, highlighting the efficiency of PBF-LB/M in creating intricate components with complex compositions and improved mechanical properties for high-temperature applications with relative ease.

Laser powder bed fusion (LPBF) titanium alloys are known to have a strong crystallographic texture; however, this is limited to β-titanium alloys, while α-titanium alloys usually show an acicular microstructure resulting from martensitic transformation. In contrast, a strong <0001>//BD texture in CP-Ti was successfully formed by optimizing the LPBF conditions. In this study, we investigated the mechanism of such a strong texture formation through detailed microstructural analysis and experimental verification. It was clarified that <0001>//BD textured grains formed as a result of grain growth in the heat-affected zone around the melt pool. The acicular grains originated from martensitic transformation are integrated by lower grain, and formed columnar grain with <0001>//BD orientation. By optimizing the LPBF conditions based on this mechanism, specifically by increasing the holding time at high temperatures and the temperature of the grain growth area, a strong crystallographic texture was also promoted in case of Ti-9 wt% Al alloy.

A new process of laser gas atomization has been developed to obtain a spherical metal powder with a particle size of 30-100 μm using laser beams of conical geometry. A process for obtaining a spherical powder in a wide size range of 50 nm - 100 μm, in which a continuous near-surface optical discharge with a temperature of 20 kK is formed using conical laser beams in an inert gas flow, into which the material is introduced in the form of a wire or a powder flow has been designed . Particle condensation is strongly and rapidly quenched by the inert gas flow, resulting in high supersaturation. The efficiency of the proposed laser methods for producing powders is up to 0.5 kg/kWh at an electric power of 16 kW, while the existing, most efficient methods of plasma and gas spraying provide an efficiency of no better than 0.1-0.25 kg/h kW. The method can be used to obtain powders from various materials - metals, ceramics, plastics, suspensions. The new process of laser centrifugal atomization has been elaborated . Melting or evaporation of the end of a rotating hollow cylinder by a laser system ensures a highly efficient process for obtaining spherical powder in the nano and micro size range with productivity up to 500 kg/h at laser power 160 kW.

Biodegradable Zn-based composites reinforced with bioactive ceramics, featuring enhanced mechanical performance, moderate corrosion rates, significantly improved biocompatibility, and specific biological functionalities, are promising candidates for biomedical implant materials. However, achieving uniform dispersion of nano-scale ceramic particles within a metallic matrix and ensuring robust interfacial properties between the bioceramic and metallic matrix remain challenging. In this study, homogeneous dispersion of beta-tricalcium phosphate (β-TCP) reinforcement within the Zn matrix was achieved through hetero-agglomeration, using silver nanowires (AgNWs) as a bridging agent. Additionally, spark plasma sintering (SPS)-induced in situ alloying between Ag and Zn resulted in strong interfacial bonding between the β-TCP reinforcement and the AgZn₃ secondary phase in the β-TCP/Zn-Ag biocomposites. The Vickers hardness significantly increased from 48.2 HV for pure Zn to 70.0 HV for 1β-TCP/Zn-Ag biocomposites. Consequently, the biodegradable 1β-TCP/Zn-Ag composite, manufactured through the AgNWs-assisted hetero-agglomeration method and subsequent SPS and HE processes, could serve as a desirable orthopedic implant material. This work offers an innovative and creative approach for the development of advanced Zn matrix biocomposites.

This study explores a novel approach of metal powder production, aiming to drive the cost-effectiveness and quality of powders for sustainable advancement in metal additive manufacturing (AM). The SMS group has refined conventional powder production for AM requirements. Additionally, in collaboration with a partner, an innovative continuous powder production process has been developed, allowing for cost-effective, large-scale production of up to 4,000 tons annually. This continuous process significantly enhances capacity, reduces production costs, and offers economies of scale. The process involves two vacuum induction melting (VIM) furnaces continuously maintaining liquid melt, atomized successively through an exchangeable nozzle under vacuum conditions, ensuring high-quality metal powders comparable to traditional methods.

Gas atomized powder is used in many other 3D printing methods such as laser and binder jet methods, and has become a mainstream raw material worldwide. Epson Atmix manufactures the powder by water atomization, but there have been few studies on 3D printing using this raw material. Although water-atomized powder is inexpensive, its filling and flowability are lower than those of gas-atomized powder, and there is a problem with extensibility when the powder is spread on the surface. In order to improve the flowability and fillability required for the BJ method, we prepared our own conventional raw powder for MIM and spherical metal powder for 3D printers with improved its circularity, and investigated how the different powder shapes affect the printing characteristics such as green body density, sintered compact density and shrinkage rate.

As a result of the evaluation, the spherical powder was found to improve the relative density of the sintered compact by 0.5% and the shrinkage of the sintered compact by 4-8%.

We believe that the improved properties of the water-atomized powder will improve the quality of the final parts in the binder jet type 3D printer manufacturing while reducing the manufacturing cost of the parts.

Inert gas atomization is a suitable technique for producing highly spherical powders used in metal additive manufacturing and other powder metallurgy techniques. Research into environmental sustainability is leading to new considerations in metal powder quality, gas atomisation processes, and raw material selection. This work presents the properties and sustainability of some gas-atomised aluminium-based powders. This study compares the characteristics of final powders made from conventional or innovative aluminum-based alloys belonging to the 2.xxx and 4.xxx series, using secondary or scrap materials. The comparison is based on granulometry, morphology, microstructure, and chemical composition, including light elements such as O, N, H, C, and S.

Cu–Zn alloys have long been used as cast and expanded copper products because they are less expensive than other Cu-based materials and have excellent workability. However, Cu–Zn alloys are not as widely used in powder metallurgy as in casting because of the problem of Zn evaporation at high temperatures. In recent years, few fundamental studies on their sinterability have been reported. In this study, the effects of various sintering conditions on the sinterability of Cu–Zn alloy powders were investigated. As the amount of H₂ in the sintering atmosphere increased, the sintering behavior improved and weight loss due to Zn evaporation increased. The decrease in Zn content was particularly pronounced on the sample surface and in the Zn-rich phase. It was also suggested that the Zn partial pressure around the sample contributed to the sinterability and weight loss.

Six different commercial subsieve powders were used for examining the effects of particle characteristics on mean particle size and specific surface area. The measurements were carried out using the air permeability and laser light diffraction techniques. The experimental data indicate that both methods give similar results for spherical powders. The advantage of laser light systems over gas permeameters is the ability to provide additional information on the particle size distribution. Irregularly-shaped powders should be analysed by both techniques relying on gas permeametry for surface area measurements and on laser light diffraction for the estimation of mean particle size and size distribution. Application of scanning electron microscopy as a complementary technique was found helpful in interpretation of data through visualization of individual particles.

Flowability of powders is commonly evaluated using flow rate (ISO 4490, JIS Z2502, MPIF 3). However, in cases where the powder is not discharged from the Hall flowmeter, flow rate cannot be applied. Furthermore, the measured value of flow rate does not necessarily correspond to the flowability in the hopper or the fillability of die during the manufacturing process of sintered parts. The die filling test is a potential method for quantitatively evaluating the flowability of powders and is expected to be an alternative evaluation method to flow rate.

In this study, the die filling test was conducted for powders with different flowabilities and the relationship with other well-known flowability evaluation methods (flow rate, the angle of repose, shear cohesion, and angle of internal friction) was investigated.

As a result, it was found that flow rate, which is commonly used for powder metallurgy powders, has limited applicability and cannot be applied to powders that do not flow out. On the other hand, other methods were able to obtain at least measurement values and enable quantitative evaluation of flowability. When limited to powders for powder metallurgy, the die filling test can be considered as a useful evaluation method that simulates the component manufacturing process.

Water-atomized (WA) steel powders are inevitably oxidized due to the chemical reaction between molten metal and water vapor. Minimization of surface oxides is essential for forming strong metallic bonds during sintering. However, the efficiency of H₂-annealing is dependant on oxide chemistry, which is rarely made of pure/stoichiometric species. The objective here was to perform an in-depth characterization of the oxides found on WA steel particles to understand their behaviour during H₂-annealing. It investigates the relationship between the chemical composition of pre-alloyed steels(Cr, Mn, Mo, Si), the chemical composition of the surface oxides and their modification due to H₂-annealing. Particular attention is given to the impact of the difference between Si(wt.%) and Mn(wt.%) contents on powder oxidation. Characterization was performed using scanning and transmission electron microscopy coupled with energy dispersive X-ray spectroscopy. Characterization before and after annealing provided insights into the dynamics of oxides reduction according to powder chemistry.

This study investigates the crucial role of powder flowability in powder-bed-based additive manufacturing (AM), with a focus on the influence of particle size variations and nanoparticle coatings. In laser powder bed fusion (LPBF) processes, maintaining optimal flow is essential for ensuring high-quality parts and a stable process. The impact of fumed silica (SiO2) nanoparticle coatings on the initial flow behavior of standard gas-atomized 316L powder, as well as powders with modified size distributions (0-45 μm, 15-63 μm, 0-63 μm), was investigated. The results indicate that nanoparticle coatings improve flowability and bulk density, demonstrating economic potential for LPBF processing of coated powders. The powders that have been coated display a higher relative density and better mechanical properties, such as improved tensile strength, when compared to their uncoated counterparts.

From an economical perspective, the use of water atomization for the production of feedstock for laser powder-bed fusion represents an interesting alternative to plasma and gas atomization. However, water-atomized powders are characterized by lower flowability. In this regard, it was previously shown that post-processing water-atomized tool steel powders with a thermo-mechanical spheroidization treatment (TMST) could improve average particle sphericity, and thus, flow properties and apparent density. In this work, the dynamic rheological properties of water-atomized tool steel powder lots that were subjected to different TMST conditions were characterized using a rotating drum apparatus and a Hall flowmeter. Additionally, an unsupervised machine learning algorithm was employed to characterize the morphological features of each powder lot. This study not only determined optimal TMST conditions to maximize flowability, but also revealed valuable insights on the relative importance of particle morphology and surface properties in governing the rheological behavior of water-atomized powders.

In electron beam melting (EBM) metal 3D printing, accurate characterization of metal particles is important for efficient layering and understanding the potential for reuse of milled particles after processing. Factors such as “flowability” and “oxygen content” of metal particles affect particle properties such as shape, sphericity, particle size distribution, specific surface area, true density, and porosity. Currently, however, the combined evaluation of these factors is insufficient and lacks clear criteria for determining the reusability of metallic particles.

Therefore, the purpose of this study was to understand the morphology and determine the reusability of Ti-6Al-4V (Ti64) metal particles by evaluating their particle characteristics. Ti64 alloy particles produced by gas atomization were evaluated as virgin particles. In addition, metallic particles produced by simple spatula grinding of the sintered compact obtained as a byproduct of molding by EBM metal 3D printing at 700 ºC and 800 ºC were used as recycled particles for comparative evaluation.

As a result, particle shape could be evaluated by SEM images and dynamic image analysis, and it was found that some of the recycled particles were slightly increased due to sintering of satellite particles, but most of the recycled particles were not significantly different from virgin particles in terms of particle size, shape, and particle size distribution. By evaluating these results together with specific surface area and porosity using the Kr gas adsorption isotherm and He gas displacement method, similar results that can be interpolated were obtained, and the morphology of each Ti64 alloy was understood, providing insight into the possibility of recycling milled particles.

Laser Powder Bed Fusion (L-PBF) has recently attracted significant attention as a new method for fabricating three-dimensional metallic parts with complex structures. For energy saving and cost reduction, the reuse of feedstock powders has been recommended for L-PBF. However, it is reported that the powder surface is usually oxidized during L-PBF process. Even though the influence of oxygen content on the mechanical properties of L-PBF builds has been investigated by some researchers, the effect of surface oxidation on the powder flowability is still controversial. In order to control the oxygen content and the homogeneity of oxidized powders, a powder oxidation approach using a wet mixing process with aqueous hydrogen peroxide was developed in this study. By taking Ti-6Al-4V alloy powder as a model material, the relationship between powder oxidation and flowability was experimentally investigated. The Ti-6Al-4V powders were successfully oxidized via the wet mixing process without changing their morphology or particle size distribution. However, the oxidized powders had better flowability rather than the raw powders. As demonstrated by STEM-EDS mappings, the surface oxide layer of oxidized powder was continuous, and its thickness was increased by approximately 30 nm comparing with the raw powder. This result indicates that the improved flowability was mainly attributed to the decrease in van der Waals force caused by the increased surface roughness of the powders. This research offers the potential of utilizing the wet mixing process with aqueous hydrogen peroxide for adjusting oxygen contents of Ti alloy powders.

Super duplex stainless steels (SDSS) combine the advantages of ferritic and austenitic steels and reach an excellent combination of mechanical and corrosion properties. The paper focuses on the production of UNS S32760 (X2CrNiMoCuWN25-7-4, AISI F55, 1.4501) SDSS powders through Vacuum induction melting Inert Gas Atomization (VIGA) with different gas atmospheres, Argon or Nitrogen. The effect of the different gases used during the melting and the atomizing on the characteristics of the final powder was investigated, in terms of granulometry, morphology, microstructure, chemical composition (also taking into account light elements such as N, O, H, C, and S). Powders were then processed by means of Laser Powder Bed Fusion (L-PBF) and microstructural features and mechanical properties of produced components were analyzed in the as processed state and after thermal treatments, properly optimized to obtain a good balancing between the α ferrite/austenite phases.

Powder degradation during additive manufacturing poses a significant challenge to achieving optimal part quality and maximal powder feedstock utilization and hence sustainability of the process. Pure copper possesses high optical reflectivity and excellent thermal and electrical conductivity. Powder bed fusion - electron beam (PBF-EB) is a promising method for fabricating pure copper parts as it can melt materials regardless of their reflectivity and operates under vacuum preventing oxidation. This study investigates the influence of pure copper powder properties and reuse on the powder surface oxide chemistry and processability by PBF-EB. Changes in powder surface chemistry were studied by HRSEM and X-ray Photoelectron Spectroscopy in virgin and reused state. Results indicate that there is evident degradation in powder properties during reuse with increase in oxygen content, connected to increase in surface oxide layer as well as transformation of CuO into Cu₂O and formation of Cu(OH)₂ on top surface during handling.

The present work was carried out as part of the French CaracPow project which is dedicated to a better understanding of the characteristics of metal powders used in the PBF-LB process for the purpose of a better consistency in mechanical properties. In this investigation, the effects of variability between powder batches as well as long-term stability are determined in terms of chemical, physical, rheological and mechanical properties for the 316L stainless steel and for IN625 alloys. Measurements of powder size distribution (PSD), sphericity, presence of satellites, tapped density and flowability were made for different powder batches. A uniform spreading of powder layers and an improved repeatability over time for PBF-LB are key factors for build-to-build consistency. This work has been performed within the framework of the French Additive Factory Hub (AFH) bringing together several research institutes and industrial end-users.

Metal Injection Molding (MIM) process is a suitable process for fabricating small and complex shaped metal parts with high production volume. Carbon fiber (CF) has high thermal conductivity and mechanical properties, thus, Metal/Carbon composites would show great properties. Especially using MIM process to fabricate the composites, orientation of the fiber would be controlled during injection molding. Also, short fiber is easily and homogeneously dispersed in the metal powder during mixing process. In this study, Copper / CF composites were fabricated through the MIM process. The effects of carbon fiber contents and orientation on the mechanical properties were investigated.

In this study, powder injection molding method was employed to produce Cu-12Al-4Ni (wt%) shape memory alloys, and the microstructural evolution of the samples was studied. The binder system used in this investigation included paraffin wax (65 wt%), high density polyethylene (30 wt%) and stearic acid (5 wt%). Feedstocks containing 63 and 64 vol% powder mixtures were produced with the selected mixing parameters, then their rheological behavior was studied. After producing the green parts using the certain injection parameters, they were subjected to debinding and sintering processes to produce the final parts. Finally, the sintered parts were characterized for their microstructure by Scanning Electron Microscope (SEM).

Molybdenum (Mo) is one of the beta-phase stabilisers in titanium, garnering significant interest by modifying the properties of commercially pure Ti (CP-Ti) suitable for biomedical applications. Being a non-toxic alloying element with reasonable cost, Mo can enhance mechanical properties through solution strengthening. In this study, five amounts of Mo content (0, 5, 7.5, 10, 15 wt.%) were added to CP-Ti manufactured by the metal injection moulding (MIM) process. Three sintering temperatures of 1100, 1150 and 1250 C for 4 h were applied. The properties of the sintered specimens were evaluated through density, impurity contents, microstructure, tensile testing, and observation of the fracture surfaces. The results indicate that higher Mo contents lead to an increased amount of beta phase and higher tensile strength from 600 to 1100 MPa with 0 to 15 wt.% Mo. However, excessively high Mo content contributes to low ductility due to the formation of TiC precipitated at the grain boundaries. In this study, the 5 wt.% Mo addition specimen shows the most balanced mechanical properties.

In the present study, we investigated the effect of the sintering temperature on the physical properties of bi-material micro-components of hydroxyapatite (HA) and 3 mol% yttria-stabilized zirconia (3YSZ) fabricated utilizing a two-component micro-powder injection molding (2C-µPIM) technique. Firstly, HA and 3YSZ powders were individually mixed with binders to prepare the feedstocks. Following micro-injection molding of the HA and 3YSZ feedstocks into the dumbbell shape, the debinding procedure was carried out. The debound samples were sintered at temperatures ranging from 1200°C to 1400°C. According to field emission scanning electron microscopy (FESEM) analysis of the microstructures, sintering resulted in the formation of a bonding between two different types of ceramic in micro-sized HA/3YSZ components. The highest relative density of 98% was achieved after sintering. The sintered HA/3YSZ micro-parts demonstrated a linear shrinkage between 11% and 19% after the sintering process.

Binders for metal injection molding (MIM) are generally composed of various chemical materials. Mixing multiple materials in production of binders are required to control binder volatilization temperature, especially for thermal binders. Polyoxymethylene (POM) is a promising ingredient of binder that is used for catalytic debinding system due to the low residue formation. Furthermore, since the volatilization temperature of POM is lower than that of polyolefin resins, POM is also suitable for thermal debinding system. However, it is difficult to use POM as a component of thermal binders because of its poor miscibility of other materials and high reactivity with inorganic powders, respectively. In this work, we have developed a new binder, which includes high flow POM and can be used for thermal debinding system. We would like to discuss some of characteristics such as reduced odor in kneading process, fluidity of feedstock, and reduced voids in sintered body.

In metal injection molding (MIM), it is important to reduce flash and flow mark as much as possible for high quality and high productivity on each MIM green parts. The back flow that occurs in injection process and the ability of injection response affect flash and flow mark. In this study, the experiment using the spiral-flow tester and the medical clip mold are carried to compare V-LINE^® injection molding machine (V-LINE^®) that plasticizes with the single screw and fills with the plunger to In-line injection molding machine (In-line). The experiment using the spiral-flow tester shows that the flow length molded by V-LINE^® is longer than that one molded by In-line. And the experiment using the medical clip mold shows that V-LINE^® can reduce flash and flow mark more than In-line.

POM based feedstock was first invented by the BASF. This feedstock system has been around for over 25 years since 1996. In China, there were over 70% of MIM companies have accepted and widely adopted MIM product manufacturing since 2002. In the early years, stainless steel and iron-based metal alloy powders were only used for POM base feedstock. After the patent expired, more than 50 Chinese companies have researched and manufactured POM based feedstock materials. Based on Dr Q own research and experience, this feedstock has also been successfully applied to other metals including metal(include cobalt, nickel, tungsten, titanium, and aluminum) and alloys. Also expanded to include ceramic materials, alumina, zirconia, and ferrite oxide. POM based feedstock can be de-binding using oxalic acid catalysis, significantly reducing the environmental hazards of PIM industry. This report provides a comprehensive description of the current status of POM based feedstock development.

Metal Injection Molding (MIM) is characterized by its ability to accommodate complex shapes, achieve high density, offer a wide range of material choices, and facilitate mass production. Despite these advantages, there has been a recognized challenge in addressing the production of hollow parts. To meet market demands, we have embarked on the development of integrated three-dimensional hollow shapes that were previously unattainable. We have now successfully achieved mass production of hollow MIM parts. This paper introduces the hollow MIM process, along with its issues and countermeasures.