Metal Powder Research Articles

Ti6Al4V Implants with Dense-Trabecular Bilayer Morphology for Bone Ingrowth: Synergy of Green Net Shaping and Sacrificial Templating.

Stress shielding in dental and orthopedic implants is a long-standing hurdle, and trabecular porous architecture to improve bone ingrowth is deemed to be a potential solution. Fabricating Ti6Al4V components with dense-porous bilayer structures is complicated with limited lab-scale and commercial success. Here, a green dough-forming technique with metal powders is successfully explored to develop heterogeneous structures with a monolith-like dense-porous interface. The porous region achieved 70% porosity with a 25 MPa compressive strength comparable to human cancellous bone. Due to its simplicity and versatility, this process is a promising solution for developing and mass-manufacturing customized designs for bone-related implants with improved bone ingrowth and osseointegration.

High-speed formation of pure copper layers via multibeam laser metal deposition with blue lasers

To realize a carbon-neutral society, it is necessary to shift from gasoline-powered vehicles to electric vehicles. Electric vehicles use copper components such as coil motors and batteries for which copper joining technology is important. Additive manufacturing is one of the most essential technologies for the next generation of manufacturing. Therefore, the technology for forming pure copper layer on a pure copper substrate is important. Laser metal deposition (LMD) is one of the additive manufacturing technologies. A blue diode laser is expected to be effective in shaping pure copper parts because light absorptance of pure copper at blue light is higher than that of near-infrared light. Thus, a multibeam LMD system with the blue diode laser in which metal powder was supplied perpendicular to the processing point and multiple lasers were irradiated from the surroundings was developed for additively manufactured pure copper. In our previous study, we succeeded in forming a pure copper layer on a pure copper substrate at a speed of 1.5 mm/s with blue diode lasers. However, an increase in processing speed was necessary for industrial application. It is considered that the improvement of energy density at the processing point and the control of heat input to the powder and the substrate by lasers are essential to improve the processing speed. Therefore, in this study, we designed an optical system with ten times higher energy density and calculated the heat input to the powder to form a pure copper layer at a speed of 10 mm/s or faster.

Empirical estimation of metal powder bed fusion technological improvement rate

AbstractThis study empirically estimates the technological improvement rate (TIR) of metal powder bed fusion (PBF) technology, widely used in aerospace, automotive, and medical industries. PBF's continuous long-term adoption growth is driven by its ability to enhance manufacturing efficiency in terms of time and raw material use, as well as its capability to produce high-quality, high-strength, complex-shaped parts. Measuring the technological development of PBF is crucial as itis enlarging its application domain and is increasingly considered a viable alternative to traditional manufacturing technologies across a broader range of applications. We resorted to the literature to collect information and assess which technical parameters are most relevant to measure the capabilities of PBF. With those, we established an ideal functional performance metric (FPM) capable of comprehensively assessing PBF's technological performance improvement. Considering all available data sources and PBF machines ever made commercially available, a data set of technical parameters was constructed. This was followed by a data curation process focusing on data availability and reliability. The resultant practical FPM was used to estimate the TIR of PBF technology. By employing regression analysis, we estimate a yearly improvement of 26.8%. This empirical rate comes as a more accurate and reliable substitute to the previously indirectly estimated patent-derived rate of 33.3%. Our findings underscore PBF's capability of keeping pace with its growing significance and wider industrial applications. The results of this study provide a key metric for those in the industry and research, confirming the rapid performance growth and establishing a standard for future industrial uses.

Electro-discharge deposition of zinc powder on 316L stainless steel: Synthesis, deposition rate, and characterization

This study investigated the potential of powder-mixed electrical discharge machining (PM-EDM) to deposit metallic powder, specifically zinc powder, on 316L stainless steel (316L SS). This study aimed to evaluate the effect of zinc (Zn) deposition on 316L SS for oil and gas application. Minitab 19 software was employed to design the experiments using screening DOE option and to analyse and model the results through screening response optimiser from Minitab 19 software. Surface morphology, microstructure and coating thickness were examined through field-emission scanning electron microscopy (FESEM) and scanning electron microscope (SEM). The results suggested an improvement in the coating thickness with an increase in powder concentration and discharge current. An average coating thickness of 91.47 μm was achieved in samples fabricated at 20 g/L powder concentration. X-ray diffraction analysis revealed the formation of hard carbides, such as Cr3C2 and TiC, on the PM-EDMed 316L SS surface. Further characterisation through energy-dispersive X-ray spectroscopy confirmed the deposition of both the tool electrode and Zn powder particles. The adhesion test confirmed that all specimens failed under 100% adhesive failure. The hydrophobicity analysis confirmed that the coated surfaces are hydrophobic. Significant improvement has been established for microhardness, wear resistance and corrosion performance. Screening results revealed that discharge current, pulse-on time, and powder concentration were the most significant parameters. The average predicted errors of 2.055%, 6.782%, and 2.396% for material deposition rate, tool wear rate, and surface roughness were achieved, respectively. These affirmed the excellent reproducibility of the model developed. This study presents a methodology for the formation of carbide- and oxide-based coatings specifically for oil and gas applications (flanges and connectors).

Life cycle assessment of metal powder production: a Bayesian stochastic Kriging model-based autonomous estimation

Metal powder contributes to the environmental burdens of additive manufacturing (AM) substantially. Current life cycle assessments (LCAs) of metal powders present considerable variations of lifecycle environmental inventory due to process divergence, spatial heterogeneity, or temporal fluctuation. Most importantly, the amounts of LCA studies on metal powder are limited and primarily confined to partial material types. To this end, based on the data surveyed from a metal powder supplier, this study conducted an LCA of titanium and nickel alloy produced by electrode-inducted and vacuum-inducted melting gas atomization, respectively. Given that energy consumption dominates the environmental burden of powder production and is influenced by metal materials’ physical properties, we proposed a Bayesian stochastic Kriging model to estimate the energy consumption during the gas atomization process. This model considered the inherent uncertainties of training data and adaptively updated the parameters of interest when new environmental data on gas atomization were available. With the predicted energy use information of specific powder, the corresponding lifecycle environmental impacts can be further autonomously estimated in conjunction with the other surveyed powder production stages. Results indicated the environmental impact of titanium alloy powder is slightly higher than that of nickel alloy powder and their lifecycle carbon emissions are around 20 kg CO2 equivalency. The proposed Bayesian stochastic Kriging model showed more accurate predictions of energy consumption compared with conventional Kriging and stochastic Kriging models. This study enables data imputation of energy consumption during gas atomization given the physical properties and producing technique of powder materials.

Characterizing the as-built surface topography of Inconel 718 specimens as a function of laser powder bed fusion process parameters

Purpose The ability to use laser powder bed fusion (LPBF) to print parts with tailored surface topography could reduce the need for costly post-processing. However, characterizing the as-built surface topography as a function of process parameters is crucial to establishing linkages between process parameters and surface topography and is currently not well understood. The purpose of this study is to measure the effect of different LPBF process parameters on the as-built surface topography of Inconel 718 parts. Design/methodology/approach Inconel 718 truncheon specimens with different process parameters, including single- and double contour laser pass, laser power, laser scan speed, build orientation and characterize their as-built surface topography using deterministic and areal surface topography parameters are printed. The effect of both individual process parameters, as well as their interactions, on the as-built surface topography are evaluated and linked to the underlying physics, informed by surface topography data. Findings Deterministic surface topography parameters are more suitable than areal surface topography parameters to characterize the distinct features of the as-built surfaces that result from LPBF. The as-built surface topography is strongly dependent on the built orientation and is dominated by the staircase effect for shallow orientations and partially fused metal powder particles for steep orientations. Laser power and laser scan speed have a combined effect on the as-built surface topography, even when maintaining constant laser energy density. Originality/value This work addresses two knowledge gaps. (i) It introduces deterministic instead of areal surface topography parameters to unambiguously characterize the as-built LPBF surfaces. (ii) It provides a methodical study of the as-built surface topography as a function of individual LPBF process parameters and their interaction effects.

Effect of Laser Powder Bed Fusion Parameters on the Evolution of Melt Pool, Densification, Microstructure, and Hardness in 420 Stainless Steel Parts

Laser powder bed fusion (LPBF) involves depositing, melting, and solidifying metal powder particles layer by layer to create 3D components. In this study, a deep fundamental understanding on how process parameters—laser power, scan speed, and hatch spacing—affect the melt pool, densification, microstructure, hardness, and thermal behavior of 420 stainless steel (420SS) parts produced by such technology is provided. The conducted investigation considers five levels of laser power and hatch spacing, and four scan speeds. Optimal single tracks, based on geometry and profile, are achieved with laser powers between 40 and 80 W and a scan speed of 10 mm s−1. In the multitrack analysis, it is indicated that a dense, smooth surface is obtained with a hatch spacing of 250 μm, corresponding to an overlapping rate of ≈30%. The 420SS samples show high densification (≈99%) and low surface roughness (≈3.62 μm). The microstructure consisted of martensite laths and retained austenite. The hardness and thermal conductivity of the samples are measured at 540 HV and 15.3 W m−1 K−1, respectively. In this study, the understanding of the process–structure–property relationships in LPBF of 420SS is expanded.

A hybrid mesoscale-continuum approach to understand and predict melting kinetics of Al powders during laser processing

Abstract Laser interaction with metallic powders during additive manufacturing (AM) leads to fast heating and cooling rates that can affect the quality of the final products due to the formation of defects. One of the first steps towards predicting microstructures generated during AM, therefore, requires an accurate understanding of the laser energy deposition mechanisms that determine the melting kinetics at the level of individual powders. The critical challenge, however, is the availability of computational methods that can model the laser energy absorption, heat transfer, and the related microstructure evolution in individual metal powders at the length and time scales of AM. This manuscript demonstrates the capability of a novel scale-bridging methodology that combines the mesoscale quasi-coarse-grained dynamics (QCGD) simulations with a continuum two-temperature model (TTM) to account for the atomistic mechanisms of laser energy deposition and microstructure evolution and predict the kinetics of melting of individual powders at the experimental time and length scales. The scale-bridging capability of the hybrid QCGD-TTM simulations is demonstrated here by investigating the laser-induced microstructure evolution in aluminum powders with various sizes ranging from 200 nm to 20 µm. The analysis of the evolution of temperature, pressure, phase fraction, and melt fronts suggests the melting mechanism is heterogeneous due to the interaction with a laser, and the melting time is observed to decrease exponentially as the laser intensity increases. The solid-liquid interface velocity can be quantified to identify correlations with interface temperatures, and the predicted values satisfy the theoretically reported limits of crystal stability of metals against homogeneous melting. In addition, the pre-melting is found at the grain boundaries of 20 µm polycrystalline aluminum powder, while a minute contribution to melting is observed. This manuscript demonstrates the capability of the QCGD-TTM method to capture laser-powder interaction and allow the investigation of the kinetics of laser melting.

Optical Particle Tracking in the Pneumatic Conveying of Metal Powders through a Thin Capillary Pipe

Optical Particle Tracking in the Pneumatic Conveying of Metal Powders through a Thin Capillary Pipe

RESEARCH ABOUT M300 MARAGING STEEL METALLIC POWDER FOR USE IN SLM 3D PRINTING

A growing number of steel components are being fabricated by 3D metal printing. Using metallic powder as the material fed into the laser is selective laser melting (SLM), one of the most popular and precise techniques. The main focus of this article is the investigation that Renishaw conducted on the powder that was supplied. The powder is made using the gas atomization method, and the powder obtained from the SLM process is then examined. The powder's morphology is analysed using scanning electron microscopy (SEM). The particles were seen to have a spherical shape, with a notable number of satellites attached to their surface. The particle size distribution (PSD) was examined and ranged from 15 to 90 µm. In addition, the porosity exhibited a range of values between 0.03% and 0.12%, with an average value of 0.07%. Additionally, the surface wettability was tested, and it was seen to display a wetting behavior (under 90◦) which provided surface energy up to 46.21 mJ.m−2.

Numerical Simulation of Gas Atomization and Powder Flowability for Metallic Additive Manufacturing

The quality of metal powder is essential in additive manufacturing (AM). The defects and mechanical properties of alloy parts manufactured through AM are significantly influenced by the particle size, sphericity, and flowability of the metal powder. Gas atomization (GA) technology is a widely used method for producing metal powders due to its high efficiency and cost-effectiveness. In this work, a multi-phase numerical model is developed to compute the alloy liquid breaking in the GA process by capturing the gas–liquid interface using the Coupled Level Set and Volume-of-Fluid (CLSVOF) method and the realizable k-ε turbulence model. A GA experiment is carried out, and a statistical comparison between the particle-size distributions obtained from the simulation and GA experiment shows that the relative errors of the cumulative frequency for the particle sizes sampled in two regions of the GA chamber are 5.28% and 5.39%, respectively. The mechanism of powder formation is discussed based on the numerical results. In addition, a discrete element model (DEM) is developed to compute the powder flowability by simulating a Hall flow experiment using the particle-size distribution obtained from the GA experiment. The relative error of the time that finishes the Hall flow in the simulation and experiment is obtained to be 1.9%.

High-Speed and High-Temperature Powder Metallurgy for Energy Efficiency and Environmental Protection

The article examines various approaches to creating industrial products from metal powders using powder metallurgy methods. The advantages of powder-metallurgical methods for the production of details in comparison with classical methods are cited. Innovative grinding bodies and grinding media are presented. Possibilities of adding micro and nano elements are considered. A high-speed and high-temperature technology for obtaining wear-resistant materials is described. Possibilities for the utilization of waste materials - glass and electronic boards - were discussed. Applications in industry, medicine, and agriculture are presented.

Mechanical and electrical properties of α-MoO3 belts under strain for flexible electronics applications

This study investigated a straightforward and cost-effective method for synthesizing α-MoO3 belts and evaluated their potential as substrates for flexible electronic devices. Transparent α-MoO3 belts, featuring millimeter-scale side lengths and micrometer-scale thicknesses, were produced through a one-step sintering process using metallic molybdenum powder. When affixed to stretchable substrates, the α-MoO3 belts demonstrated robust mechanical stability under continuous and sustained tensile strain in the longitudinal direction. The belts exhibited a transmittance exceeding 68 % in the visible and near-infrared light regions. The current between gold dots on belts fixed to a stretchable polydimethylsiloxane substrate increased with the application of tensile strain. Furthermore, a CoFe2O4 thin film deposited at elevated temperature onto an α-MoO3 belt exhibited significant magnetic anisotropy. These findings introduce a novel and efficient approach for fabricating highly crystalline thin films on stretchable and bendable substrates using α-MoO3 belts.

Grain-Boundary Engineering of Na3Bi/NaF Dual-Functional Heterogeneous Protective Layer for Highly Stable Sodium Metal Anodes

Sodium-metal batteries have been extensively recognized as a potential alternative to lithium-metal batteries. However, the huge volume expansion, inhomogeneous distribution of the electrical field, and sluggish Na+ diffusion at the electrolyte/electrode interface are insurmountable challenges to achieving high cycling performance and a long lifespan. In this work, a dual-functional heterogeneous protective layer consisting of Na3Bi/NaF was constructed on the surface of metallic sodium (abbr. BiF3/Na) by the spontaneous reduction reactions between metallic sodium and BiF3 powder at room temperature. Attributing to the in-situ formation of rich grain boundaries and the built-in electric field between the components, the charge transfer, Na+ diffusion rate as well as mechanical strength of the BiF3/Na anode were extensively improved. Consequently, the sodium metal anode with the Na3Bi/NaF dual-functional heterogeneous layer achieves an excellent cycling capability and long cycling lifespan of more than 2000 hours at a large current density of 2 mA cm-2 and an area capacity of 1 mAh cm-2. In addition, by further matching with the commercialized NaNi1/3Fe1/3Mn1/3O2 (NFM) cathode, the prepared BiF3/Na||NFM full cell exhibits high durability (68.8 mAh g-1 after 2000 cycles at 2 C). This work utilizing grain boundary engineering has provided a promising strategy for achieving dendrite-free sodium metal anodes and high-energy density sodium metal batteries.

Acoustic emission monitoring of a laser powder bed fusion process

Additive manufacturing (AM) metal parts offers opportunities for various industrial applications. From individual production of spare parts for unique mechanical components to prototyping of complex structures, the possibilities of production using the additive manufacturing process are manifold. One common AM technique is the Laser Powder Bed Fusion (PBF-LB/M) process, where a laser is used to selectively melt metal powder and create the parts layer wise as designed in a model. During manufacturing certain defects like pores, cracks and lack of fusion may be created in the built parts. As AM parts often have complex geometries, a postprocess non-destructive testing is difficult or even not possible. Thus, different optical monitoring techniques are applied to detect flaws during the build process with the aim to detect and repair defects right away during the manufacturing process. However, optical monitoring system require a clear view of the melt pool and quite expensive equipment. Acoustic monitoring by AE sensors attached to the built plate would be a cheaper alternative which also can be used without visual contact to the building chamber. This paper shows a first approach of an AE based process monitoring. The build plate of a PBF-LB/M machine therefore was adapted to hold four AE sensors that are then used to monitor the process. The build process itself creates AE signals caused by the melting and cooling and the mechanical application of powder. The formation of pores and cracks is expected to create additional acoustic emissions that will be distinct from the AE pattern from the printing process. This AE signals can be linked to the different layers of the printed part or in the long run to the laser position. Results from the first tests in a customized LPBF machine will be shown as well as the implementation of AE into the PBF-LB/M machine.

УТИЛИЗАЦИЯ МЕТАЛЛИЧЕСКОГО ПОРОШКА ВЫСОКОУГЛЕРОДИСТОГО ФЕРРОХРОМА МЕТОДОМ САМОРАСПРОСТРАНЯЮЩЕГОСЯ ВЫСОКОТЕМПЕРАТУРНОГО СИНТЕЗА (СВС)

This article discusses the methods of recycling high-carbon ferrochrome metal powder by self-propagating high-temperature synthesis. The article is devoted to the study of aspiration metal dusts formed during the production of ferroalloys. The article analyzes the composition of the source material, its physicochemical properties, and the impact on the testing process. The publication touches upon the relevance of this topic and the advantages of the self-propagating high-temperature synthesis method. Particular attention was paid to comparative analyses of this method from other traditional material processing processes. This article will help to consider the problem of environmental pollution and the impact of traditional metallurgical processes on the ecosystem. The authors also analyze in detail the physical properties of the original powder samples and their combustion temperature mode. The publication shows the process flow charts, laboratory devices, and the type of resulting material. This article provides a detailed analysis of the types of laboratory devices, their physical and mechanical properties. The publication provides a thorough and detailed chemical analysis of the resulting material. In the course of the study, the expected results were obtained, which are presented in the form of tables and a figure. The article consists of an introduction, main part, conclusion, conclusion and list of references.

Effect of powders recycling on microstructure evolution and wear mechanism of plasma sprayed Ni625-WC composite coating

The utilization rate of metal powders during the preparation of plasma-sprayed coatings is typically below 70 %, which has raised significant concerns regarding efficiency. The microstructure evolution and wear mechanism of plasma-sprayed Ni625-WC composite coatings with received powders (C-p1) and recovered powders (C-p2) were studied to investigate the feasibility of powder recycling. The results showed that the boundary layer at WC particles in C-p2 was 2.84 μm thicker than that in C-p1. Decarburized WC products were dispersed nucleation to form block M23C6 at the boundary of WC particles and within Inconel 625 matrix in C-p1. In contrast, the larger contact area of block M23C6 after initial heating promoted the nucleation and growth of acicular M23C6 in C-p2. In addition, the wear rate of C-p2 is 9.1 % lower than that of C-p1. Although the higher elastic modulus (E) of C-p1 caused the Inconel 625 matrix to adhere more strongly to WC particles, resulting in higher degree adhesive wear rather than exfoliations and less adhesion in C-p2, the presence of harder and more uniformly distributed acicular M23C6, and higher microhardness (H)/E ratio in C-p2, improved the wear resistance.

Effective reduction of iron impurities in recycled aluminium-silicon alloy type LM-6 through sedimentation and filtration with synthesized Mn, Cr and Zr transition metal powders

Abstract In secondary aluminium recycling, impurity reduction, especially of iron, is a significant challenge as it deteriorates the material quality in the aluminium melt. Recycled aluminium alloys are widely used in various industries, including automotive, marine, and structural engineering. Specifically, LM-6 aluminium alloy is commonly used in automotive engine parts and transmission cases. This research focused on reducing the excessive iron content in LM-6 alloy scrap. Elements like manganese (Mn), chromium (Cr) and zirconium (Zr) were added to the melt in form of synthesized powders to form intermetallic compounds. These powders will also act as grain refiners, neutralizers and reducing the detrimental effects on the alloys. The powders were synthesized using the ball milling method with a ball to powder ratio of (5:1) to enhance mixing and amalgamation with the melt. The melt was held at an optimized temperature of 640 ± 10 °C to promote the formation of intermetallic sludge, encouraging the sedimentation of aluminium-iron (Al-Fe) intermetallic phases. XRD confirmed the formation of AlMn, AlCr, AlZr with other phases. After sedimentation, a glass fabric mesh with a pore size of 200 μm was used to effectively filter out β-iron during the filtration process. This technique reduced iron impurity in the melt by 50%–60%. As a result, the mechanical properties of the recycled aluminium improved significantly: hardness increased by 14%, and tensile strength increased by 36%. The wear and corrosion resistance of the material also improved due to the incorporation of the synthesized powders. SEM analysis revealed the plate-like formation of iron structures and confirmed the presence of the manganese, chromium, and zirconium powders in the metallographic analysis.

Microstructure analysis of SS316L using Selective Laser Melting

Abstract Additive manufacturing has emerged as a prominent and expanding domain in materials engineering, driven by a rising need for customized, highly accurate, and readily available production. Applying the selective laser melting (SLM) technique further is delayed by the layer-by-layer melting and solidification of the metal powder. The impeller constructions were extracted from a substrate, with the bending curvature as an indicator of the stress level. This research aims to analyze the quality of impeller components, surface roughness, and microstructural features of components made for the SS316L. The microstructure examinations show the part is free from the surface and internal defects are verified.

100 years of autoclaved aerated concrete

Autoclaved Aerated Concrete [AAC], a revolution in thermal insulation and energy-efficient construction, was invented by Dr Axel Eriksson in Sweden in 1923. He developed a process for curing a special mixture of lime, metal powder, and a substance containing silica. The resulting steam-cured concrete had good thermal insulation, relatively high strength, high fire resistance, and could be produced economically. Carl August Carlén, who ran a family business, was granted a license to produce AAC in 1928. After a successful introduction in Sweden, AAC production became international in 1937. The use of license systems allowed third companies to invest in AAC, leading to rapid international expansion. Germany and Poland became leading centres of expertise and allowed AAC to expand on a global scale. As we approach the era of regulatory measures to meet Europe’s climate change targets AAC plays a significant role. This article presents the history and development of autoclaved aerated concrete over the last 100 years. The most important issues concerning the standardization of the production and use of autoclaved aerated concrete are also discussed.