Powder Production Methods Research Articles

Multiphysics modeling of thermocapillary force driven pore elimination from liquid metal droplets for manufacturing pore-free powders for additive manufacturing

Gas atomization (GA) is a widely adopted method for metal powder production, involving the atomization of molten metal using pressurized gases. Despite its prevalence in additive manufacturing (AM), GA-produced powders often contain pores that can transfer to the as-built parts to deteriorate part quality. Here, we report an approach to achieve pore-free gas-atomized metal powders by inducing a reversed thermal gradient through rapid heating. The resultant thermocapillary force drives the pores out of the molten metal droplets. We demonstrate the feasibility of utilizing rapid heating to eliminate pores from droplets of different metal alloys, using high-fidelity simulation. Furthermore, we derive an analytical model to estimate the critical thermal gradient needed for pore-free powder production.

Evaluating Ti-6Al-4V for Laser Direct Energy Deposition: Insights from Powder Metallurgy Techniques

Laser Direct Energy Deposition (LDED) is a highly precise additive manufacturing technique that enables the creation and repair of complex metal components by melting and depositing metal powders. This study comprehensively evaluates Ti-6Al4V alloy within the LDED framework, highlighting its performance relative to other metals such as stainless steel, Inconel, and aluminum alloys. Ti-6Al-4V, a titanium-based alloy known for its exceptional strength-to-weight ratio, fatigue resistance, and corrosion resistance, is scrutinized for its advantages and limitations in the LDED process. The research includes a detailed comparison of mechanical properties, thermal behavior, and cost-effectiveness of Ti-6Al-4V against other common LDED metals. Additionally, the study explores the impact of powder metallurgy techniques on the deposition quality and performance of Ti-6Al-4V, focusing on aspects such as powder production methods, particle size distribution, and alloying effects. Real-world applications and case studies from industries including aerospace, automotive, and medical engineering are examined to illustrate the practical advantages of Ti-6Al-4V. The paper concludes by identifying key challenges and opportunities associated with Ti-6Al-4V in LDED and offering recommendations for future research and practical applications. This comprehensive evaluation aims to enhance understanding of Ti-6Al-4V's role in LDED and guide its optimized use in advanced manufacturing contexts

Powder Manufacturing Techniques: A Review

The growing need for advanced materials has placed a significant emphasis on the production of top-tier metal powders. To fulfill this demand, several established powder production methods have emerged, aimed at delivering high-purity metal powders. This review paper explores the various techniques used in the production of metal powders, addressing their importance in meeting the evolving requirements of modern manufacturing. Keywords: Atomization, Ball Milling, Melt Spinning, Electro-decomposition.

Comparison of ultrasonic and other atomization methods in metal powder production

The results showed that the UA powder has a finer average particle size with a narrower statistical distribution of particles than those made by the GA method. Because the UA powder has a higher sphericity and lower porosity, Generally, UA offers better-quality powders in terms of properties such as higher tap density, better flowability and low oxygen content.Ultrasonic atomization (UA) with melting raw material by an electric arc. Characterisation of the powders: particle size distribution (PSD), density, and flowability were carried out. Other parameters, such as microstructure, deviation in the chemical composition and powder surface morphology, were also investigated.The results showed that the UA powder has a finer average particle size with a narrower statistical distribution of particles than those made by the GA method. Because the UA powder has a higher sphericity and lower porosity, Generally, UA offers better-quality powders in terms of properties such as higher tap density, better flowability and low oxygen content.As an example of semi-industrial scale application of the UA system, the Ti6Al4V and TiAl powders were produced after remelting the wire. The UA system is commercially available for processing any metallic material.The test campaign results showed that the Ti6Al4V powder produced by the ultrasonic atomisation has a similar or better quality as those available from large-scale gas atomisation plants.The new method of UA powder production was analysed in terms of key powder parameters. The properties of the titanium-based powder produced this way were analysed with a view to future applications.

Impact of variability of cotton gin trash on the properties of powders prepared from distinct mechanical approaches

Cotton gin trash (CGT), a large quantity by-product of cotton ginning process can differ in its contents among different seasons, cotton harvesting methods and ginning processes, due to its complex mixture. Finding a sustainable and constant powder fabrication method across different variety of CGT is important for practical application of CGT powder. However, the impact of variability of CGT and the powder preparation methods on the properties of CGT powder have not been addressed in the literature so far. In this study, achieving micro-sized powder from CGT was targeted and difference in the particle size and properties of the prepared powders were investigated in relation to their fractional content across different batches and drying techniques. This will facilitate choosing the right method to reach desired particle size and properties of CGT for a targeted application. Three different batches of CGT were collected from New South Wales, Australia, across three different years (2017, 2018, and 2022). The micro-sized CGT powders were then fabricated through mechanical milling and using two different methods: spray drying and ring grinding. A wide range of micro-sized particles (4.9–92.6 μm) was achievable from CGT by varying the milling time and drying method. Though the cotton fibre content affected particle size of the milled slurry, its impact was found minor when the milled slurry was converted into dried CGT powder. The powder morphology and chemical structure of CGT powder from different batches were not significantly different though the crystallinity index was found higher for the samples with higher amount of cotton fibres. The thermal stability of powders was mainly affected by milling time, drying technique, and fibre content though the impact was minimal. The moisture absorption of the CGT powder was found higher for ring ground powders, which was further improved by lower cotton content. Overall, this study provides an applicable and sustainable powder production method which could be used to optimise milling times, and drying techniques across different CGT sources to obtain required particle size for utilisation of CGT, such as composite reinforcement. • Reporting a sustainable and constant cotton gin trash (CGT) powder fabrication method. • A wide range of micro-sized CGT particles (4.9–92.6 μm) was produced. • Drying method was found more impactful on CGT powder size rather than CGT variability.

Development of Powdered Mixed Green Tea and Okra Beverage Product by Spray Drying

Thai herbal juices tend to lose nutrients during heat processing. Spray-drying has been one of the most well-known methods of powder production, which involves the transformation of liquid material into dried particles. The study performed the suitable conditions of spray drying for green tea and okra powder qualities. Maltodextrin as a carrier at concentrations of 10, 20, and 30 percent were added to mixed green tea and okra powder. Three inlet and fixed outlet temperatures of 150, 160, 170 and 75C, respectively, were also analysed. Physicochemical properties such as colour, moisture, water activity, pH, yield percentage total phenolic and antioxidant inhibition percentage (DPPH, FRAP and ABTS assay) were assessed, while sensory tests were also performed. The inlet temperature of 150C, maltodextrin 10% showed the highest values of the three assays in terms of antioxidant inhibition percentage (DPPH, ABTS (VEAC), (TEAC) and FRAP assays) and total phenolic compound were 0.235%, 0.974 mM/g, 0.696 mM/g, 0.962 mM Fe+2 /g and 0.235 ppm, respectively. A sensory test of each product’s overall acceptability was performed by 30 untrained panelists using the ranking test. The results revealed that the inlet temperature of 150C, maltodextrin 30% was the most accepted (the highest yield percentage), while the inlet temperature of 170C, maltodextrin 30% was the least accepted. The information obtained describes the most exceptional advantages of the spray-drying method for the production of food particles. Further, the potential of this technique and more advanced equipment to develop processes and industrial-scale processes is essential to the bench-to-bedside translation of innovative instant powdered herbal Thai beverage products.

A Comparative Study on Laser Powder Bed Fusion of Differently Atomized 316L Stainless Steel.

The significant growth of Additive Manufacturing (AM), visible over the last ten years, has driven an increase in demand for small gradation metallic powders of a size lower than 100 µm. Until now, most affordable powders for AM have been produced using gas atomization. Recently, a new, alternative method of powder production based on ultrasonic atomization with melting by electric arc has appeared. This paper summarizes the preliminary research results of AM samples made of two AISI 316L steel powder batches, one of which was obtained during Ultrasonic Atomization (UA) and the other during Plasma Arc Gas Atomization (PAGA). The comparison starts from powder particle statistical distribution, chemical composition analysis, density, and flowability measurements. After powder analysis, test samples were produced using AM to observe the differences in microstructure, porosity, and hardness. Finally, the test campaign covered an analysis of mechanical properties, including tensile testing with Digital Image Correlation (DIC) and Charpy’s impact tests. A comparative study of parts made of ultrasonic and gas atomization powders confirms the likelihood that both methods can deliver material of similar properties.

Bioactive and Physicochemical Properties of Exotic Fruit Seed Powders: Mango (Mangefiera indica L.) and Rambutan (Nephelium lappaceum L.) Obtained by Various Drying Methods

Exotic fruits, which are becoming more and more popular in European countries, contain seeds, which are an unused and useless byproduct of fruit processing. Research conducted in recent years suggests that these unused waste products can be a source of nutrients and bioactive compounds in much more concentrated amounts than those found in the flesh of the fruit. Research on the physicochemical properties and the content of bioactive compounds in fruit seeds may allow the assessment of the possibility and purposefulness of their wider application in the production of functional food. Therefore, the aim of this study was to determine the physicochemical and bioactive properties of exotic, tropical fruit seed powders, such as mango (Mangefiera indica L.) and rambutan (Nephelium lappaceum L.) seeds, obtained by convective drying (CD) and sublimation drying (FD). In the tested powders, the water-holding capacity and water solubility were determined, the color was measured using the ‘electronic eye’ instrumental method, the taste profile was determined using the ‘electronic tongue’, and the content of selected bioactive compounds—such as tannins (titration method), total polyphenols and antioxidant activity was also determined using the spectrophotometric method. It was found that the studied powders were characterized by low water-holding capacity (1.2–1.6 g/1 g of powder), low solubility in water (9.5–17.4%), neutral color and varied taste profile, depending on the origin of the tested powder. Rambutan seed powders were characterized by a more bitter taste with a higher umami-flavor intensity compared to mango seed powders, which showed a more intense acidic and sweet taste. The conducted research shows that the applied methods of powder production, i.e., drying (to similar aw values) by convection vs. sublimation, had a much greater impact on changes in the content of bioactive compounds than on the tested physicochemical parameters. The freeze-dried seed powders were characterized by a higher content of polyphenolic compounds and a higher antioxidant activity than convection-dried seed powders. Considering the high content of polyphenols and high antioxidant activity, the studied powders may find applications in the production of dietary supplements and in the design of functional foods. Due to the low water solubility index, mango and rambutan powders can be used in the design of products where particle sensitivity is indicated. The use of the investigated exotic fruit seed powders, i.e., mango and rambutan, may not only be beneficial for nutritional reasons, but also may contribute to the reduction of post-production waste, in line with the recently widespread “zero waste” trend.

Additive manufacturing of aluminum metal matrix composites: Mechanical alloying of composite powders and single track consolidation with laser powder bed fusion

The thermomechanical properties of particle-reinforced metal matrix composites (MMCs) are attractive for many structural applications, but fabrication of MMC parts with conventional methods is difficult, costly, and typically limited to simple geometries. Additively manufacturing particulate MMCs with laser powder bed fusion (LPBF) would be an ideal method, but the laser consolidation of these materials has been largely unsuccessful in matching the properties of conventionally produced MMCs. The challenges include spreading the heterogeneous powder, distributing small ceramic particles, and forming a strong bond between the metal and the ceramic. Here, by mechanically alloying AlSi10Mg and TiB 2 , we manufacture highly-reinforced aluminum composite powders with morphology and composition tailored for LPBF process conditions. We show that this powder flows and packs similarly to gas atomized aluminum powder and can be consolidated into smooth, continuous tracks. Moreover, the method of feedstock powder production is scalable and commercially viable. Our results demonstrate conditions under which MMCs with high ceramic loading can be produced by additive manufacturing, potentially opening up many new applications for these high-performance materials.

Aspects of the Powder in Metal Additive Manufacturing: A Review

The most widely used metal additive manufacturing processes utilize powder that is spread or fed onto a building platform. Although there are reviews of the literature on some aspects of the powder, many aspects have been under-reviewed or unreviewed. The present work is a review of the literature on these aspects. Articles published in the open literature through the end of February 2022 were collected by consulting highly regarded relevant bibliographic databases, such as Google Scholar and Science Direct. The aspects reviewed were emerging methods of powder production, methods used to improve the quality of a powder after production by a well-established method, influence of variables of well-established powder production methods on powder properties, influence of powder production method on powder properties, and influence of powder reuse on properties of powders of a wide collection of alloys. One key finding was that with regard to powder reuse, the only consistent finding is that it leads to increase in the oxygen content of the powder. Another key finding was that the literature on the aspects of the literature reviewed herein contains many shortcomings and gaps, which suggest potential areas for future research, such as techniques for optimization of process variables for a given combination of metal powder and powder production method and development of methods for production of powders of new/emerging metallic materials.

Characterization and differentiation of aluminum powders used in improvised explosive devices. Part 2: Micromorphometric method refinement and preliminary statistical analysis.

Aluminum (Al) powder is commonly encountered in improvised explosive devices (IEDs) as a metallic fuel due to its availability and low cost. Although available commercially in powder form, amateur bomb-makers also produce their own Al powder via simple methods found online. In order to provide investigative leads and forensic intelligence, it is important to evaluate not only the composition of homemade devices, but also to distinguish between the various forms of Al powder they contain. To achieve this goal, a method using automated microscopy in combination with statistical techniques has been demonstrated to have the potential to provide source discrimination and investigative leads in source attribution of Al powders in IEDs. The present research refined this method and investigated 59 industrially and amateurly produced Al powder sources with seven subsamples per source using two traditional linear discriminant analyses (LDA), one with a standard data split for training and testing, and another using leave-one-out cross-validation. Averaging the classification accuracies for the two LDA-based analyses, LDA has the ability to correctly classify 59.26%, 83.35%, and 80.69% of the samples based on their powder source, type, and production method, respectively. This classification accuracy represents a 3407%, 317%, and 61.38% increase in accuracy from random class assignment, respectively. Further, in most instances of incorrect data attribution to a particular source, the subsample has been misidentified with another sample of the same powder type or production method.

Advanced Functional Metal-Ceramic and Ceramic Coatings Deposited by Low-Pressure Cold Spraying: A Review

Based on the recent analysis of various databases, cold spray (CS), the newest method among thermal spraying technologies, has received the unabated attention of hundreds of researchers continuously since its invention in the 1980s. The significance of CS lies in the low process temperature, which usually ensures compressive residual stresses and allows for the formation of coatings on a thermally sensitive substrate. This paper concerns the low-pressure cold spray (LPCS) variant employed for forming metal matrix composites (MMCs) with high ceramic contents and all-ceramic coatings. At the very beginning, the influence of LPCS process parameters on deposition efficiency (DE) is analysed. In the next part, the most useful feedstock powder preparation techniques for LCPS are presented. Due to the combination of bottom-up powder production methods (e.g., sol-gel (SG)) with LCPS, the metal matrix that works as a binder for ceramic particles in MMC coatings can be removed, resulting in all-ceramic coatings. Furthermore, with optimization of spraying parameters, it is possible to predict and control phase transformation in the feedstock material. Further in the paper, differences in the bonding mechanism of metal–ceramic mixtures and ceramic particles are presented. The properties and applications of various MMC and ceramic coatings are also discussed. Finally, the exemplary direction of CS development is suggested.

Design and Production of a New FeCoNiCrAlCu High-Entropy Alloy: Influence of Powder Production Method on Sintering.

The structure of FeCoNiCrAl1.8Cu0.5 high-entropy alloys (HEA) obtained by two different routes has been studied. The selection of the composition has followed the Hume–Rothery approach in terms of number of itinerant electrons (e/a) and average atomic radius to control the formation of specific phases. The alloys were obtained either from a mixture of elemental powders or from gas-atomised powders, being consolidated in both cases by uniaxial pressing and vacuum sintering at temperatures of 1200 °C and 1300 °C. The characterization performed in the sintered samples from both types of powder includes scanning electron microscopy, X-ray diffraction, differential thermal analysis, and density measurements. It was found that the powder production techniques give similar phases content. However, the sintering at 1300 °C destroys the achieved phase stability of the samples. The phases identified by all techniques and confirmed by Thermo-Calc calculations are the following: a major Co-Ni-Al-rich (P1) BCC phase, which stays stable after 1300 °C sintering and homogenising TT treatments; a complex Cr-Fe-rich (P2) B2 type phase, which transforms into a sigma phase after the 1300 °C sintering and homogenising TT treatments; and a very minor Al-Cu-rich (P3) FCC phase, which also transforms into Domain II and Domain III phases during the heating at 1300 °C and homogenising TT treatments.

Novel Cold Crucible Ultrasonic Atomization Powder Production Method for 3D Printing.

A new powder production method has been developed to speed up the search for novel alloys for additive manufacturing. The technique involves an ultrasonically agitated cold crucible installed at the top of a 20 kHz ultrasonic sonotrode. The material is melted with an electric arc and undergoes pulverization with standing wave vibrations. Several different alloys in various forms, including noble and metallic glass alloys, were chosen to test the process. The atomized particles showed exceptional sphericity, while powder output suitable for additive manufacturing reached up to 60%. The AMZ4 metallic glass powder remained amorphous below the 50 μm fraction, while tungsten addition led to crystallization in each fraction. Minor contamination and high Mn and Zn evaporation, especially in the finest particles, was observed in atomized powders. The innovative ultrasonic atomization method appears as a promising tool for material scientists to develop powders with tailored chemical composition, size and structure.

Synthesis of TiH2 powder from ilmenite using MgH2 under H2 atmosphere

The present study introduces a novel method for synthesis titanium hydride (TiH2) powder at low-temperature from ilmenite for powder metallurgy. The ilmenite converted to titanium tetrachloride (TiCl4) gas through the chlorination process. Next, TiCl4 reacted with magnesium hydride at different times and temperatures to produce TiH2 under a hydrogen atmosphere. The phase and morphology analysis of the obtained powders were studied using X-Ray Diffraction and Scanning Electron Microscopy techniques. The results indicated that the increase of reaction time and temperature enhanced the formation of TiH2 powder, which is a promising method for low-cost titanium hydride powder production.

Powder production of from low-alloy steel by flame atomization

The advantages of plasma atomization technology in comparison with other methods of powder production for additive technologies are shown in this paper. Investigations of powders obtained by plasma atomization from welding wire sv-08G2S (similar to ER70S-6) with a diameter of 0.8 mm have been carried out. The size of the powders, their shape, chemical composition, microstructure and microhardness have been investigated.

Powder based additive manufacturing for biomedical application of titanium and its alloys: a review.

Powder based additive manufacturing (AM) technology of Ti and its alloys has received great attention in biomedical applications owing to its advantages such as customized fabrication, potential to be cost-, time-, and resource-saving. The performance of additive manufactured implants or scaffolds strongly depends on various kinds of AM technique and the quality of Ti and its alloy powders. This paper has specifically covered the process of commonly used powder-based AM technique and the powder production of Ti and its alloy. The selected techniques include laser-based powder bed fusion of metals (PBF-LB/M), electron beam powder bed fusion of metals (PBF-EB/M), and directed energy deposition utilized in the production of the biomaterials are discussed as well as the powder fed system of binder jetting. Moreover, titanium based powder production methods such as gas atomization, plasma atomization, and plasma rotating electrode process are also discussed.

Cryogenic mechanical alloying of aluminum matrix composites for powder bed fusion additive manufacturing

Cryogenic mechanical alloying (cryomilling) was employed to fabricate aluminum matrix composite powder feedstock for additive manufacturing. The high energy milling of the powder system induces a homogenous distribution of reinforcement particles in the matrix powder by recurrent fracture and cold welding. In this study, aluminum matrix composite feedstock were produced via different cryomilling techniques at varying compositions, powder charges, and milling times. As-milled powders were characterized for particle size distribution, morphology, and homogeneity. Resultant powder demonstrated varying characteristics correlated to milling parameters. Powder metallurgy samples were also fabricated to understand as-sintered reinforcement distribution and the resultant strengthening. This research provides an indication of cryomilling capabilities to become an effective method for custom alloy powder production for powder bed fusion additive manufacturing.

Conductive hydro drying as an alternative method for egg white powder production

The study aimed to evaluate the conductive hydro drying (CHD) process of egg white. The physical and functional properties of egg white dried in a batch type CHD at three different temperatures (40, 45 and 50 °C) were compared with spray-dried (SD) and freeze-dried (FD) egg white. Various physical and chemical characteristics were analyzed for the egg white powders. Moisture content (3–4%) and water activity (0.22–0.54) were found to be less in CHD powders than other techniques. In the case of powder characteristics, CHD drying showed superior results with good flowability and solubility (78–84%). Degradation of fluorescence intensity was observed in SD egg white. SEM analysis of egg powder showed a flaky structure of CHD samples and spherical and porous structure in SD and FD flakes. CHD method demonstrated better results in gel formation, color value, the hardness of gel, and emulsion properties of the egg. Owing to foam formation and stability, CHD and FD egg white showed positive effects exhibited more excellent stability and foam formation than spray drying. No significant changes were observed in the functional properties of the egg white protein. The CHD process required lesser drying time to dehydrate egg white with added convenience in terms of simplicity dryer design. Overall, the results confirmed that the CHD method is an effective alternative method for drying egg white.

Study on thermodynamic equilibrium and character inheritance of cobalt carbonate decomposition

Presently, the main cobalt powder production method is the reduction of cobalt carbonate, and the decomposition process significantly influences the properties of the ensuing cobalt powder. Thus, the objective of this study was to investigate CoCO3 decomposition using thermodynamic simulations and calculations, as well as experiments. The results obtained led to the conclusion that in the absence of oxygen, CoCO3 primarily decomposes into CoO and CO2. However, in the presence of oxygen, it preferentially undergoes oxidation decomposition, generating Co3O4 and CO2, while the unreacted CoCO3 subsequently decomposed forming more CoO when O2 was exhausted. Additionally, Co3O4 decomposed to CoO and O2 at high temperatures. TG-DSC-MS analyses showed that the temperature at which CoCO3 decomposed into CoO was 332 °C. The analysis of the CoCO3 decomposition process performed in an inert atmosphere showed that the decomposition product, CoO was generated at temperatures above 300 °C. Furthermore, SEM results showed that the morphology of the CoO obtained depends on that of the raw material (CoCO3), and a higher temperature induced agglomeration; thus, increasing CoO size. Lower decomposition temperatures, higher gas flow rates, and lower heating rates resulted in a decrease in CoO particle size.