Alloy Powders Research Articles

Hot Isostatic Pressing of Additive Specimens, Grown from IN718 Alloy Powder Obtained by Gas Atomization

Hot Isostatic Pressing of Additive Specimens, Grown from IN718 Alloy Powder Obtained by Gas Atomization

Machine learning in additive manufacturing——NiTi alloy’s transformation behavior

The laser powder bed fused NiTi alloys (LPBF-NiTi) demonstrate shape memory functionality and superelasticity as a result of their distinctive phase transition characteristics. Nevertheless, achieving precise control and regulation of the phase transition temperature poses a challenge, influenced by factors like powder composition and process parameter. In this study, a feature screening strategy and machine learning (ML) method were employed to predict and regulate the phase transition temperature of LPBF-NiTi alloy, offering a more efficient and cost-effective alternative to traditional experimental methods of regulation and control. Specifically, accuracy analysis was performed on LPBF-NiTi phase transition datasets with varying compositions and process conditions utilizing generalized regression neural network (GRNN), and other methods. The findings indicate that the interpretable features extracted through the selection strategy outlined in this study when combined with the GRNN model, demonstrate a high level of prediction accuracy (R2 = 0.97). To investigate the accuracy of the model, this study utilized various process parameters to fabricate NiTi alloys with different compositions from Ni50.8Ti49.2 alloy powder. Using this model, the study identified a novel, larger window of optimal LPBF processing that allows for controllable complex phase transitions.

Microstructural evolution and high temperature hot corrosion behaviour of AlCoCrFeNiTi high-entropy alloy coatings

The fuels used contain undesirable impurities such as Na, V, K, S, and Mg in gas turbine engines. These impurities react with hot components under service conditions, leading to the deterioration of the thermal barrier coatings (TBCs) structure and the formation of hot corrosion damage. In this study, metallic powders containing CoNiCrAlY were deposited as bond coat on Inconel 718 superalloy material using high velocity oxygen fuel (HVOF) coating technique. High entropy alloy (HEA) powder containing AlCoCrFeNiTi was synthesized as coating material using mechanical alloying (MA) method. AlCoCrFeNiTi powders were produced using atmospheric plasma spray (APS) coating technique. The produced coating system was subjected to hot corrosion tests at 700 °C and 800 °C temperatures for different time periods in corrosive environment conditions containing Na2SO4 (sodium sulfate) and V2O5 (vanadium pentoxide). Hot corrosion behavior of the coating system was determined, damage formations and degradation processes were investigated in detail. As a result of the determination and synthesis of HEA powder materials, production of coatings, experimental studies and hot corrosion test studies under service conditions, it was seen that the Ti-containing AlCoCrFeNi HEA coating system has usable qualities without any damage such as cracking, buckling or spalling.

Surface chemistry characterization of AA2014 aluminum alloy powder through triboelectric charging

Traditional characterization techniques for powders primarily focus on bulk properties, often neglecting the critical role of surface chemistry variations that influence the performance in applications such as additive manufacturing. The method presented in this work addresses this gap by utilizing triboelectric charging concept to gain a comprehensive understanding of powder surface state under varying environmental conditions. In particular, the study investigates the detection of surface chemistry variations of AA2014 powder caused by an exposure to various relative humidity (RH) levels through a change in triboelectric charging behavior. The surface variations are analyzed in parallel with X-ray photoelectron spectroscopy (XPS). The findings reveal a direct correlation between elevated RH and increased hydroxide species content at the surface of the powder. The triboelectric charging experiments demonstrated a significant RH-dependent variations of charge accumulation, with higher humidity levels leading to reduced static charge buildup on the powder particles. The charge accumulation behavior in the powder was fitted with the compressed exponential relaxation model. The results showed that each surface chemical species exhibits a distinct correlation between charging rate and charge accumulation, confirming the method's effectivity to detect subtle variations in surface chemistry. The variations in the exponent of the fitted model were shown to be characteristics to the surface scale of the powder particles.

One-step synthesis of spherical Al3Ta alloy powder by electrolyzing solid Ta2O5 in molten fluorides

One-step synthesis of spherical Al3Ta alloy powder by electrolyzing solid Ta2O5 in molten fluorides

The influence of the granulometric composition of powders of steels and precision alloys and their melting modes by LPBF ON porosity

The results of the experimental study of powder materials of various brands and classes (stainless steel, precision soft and hard magnetic alloys) are presented, the influence of their parameters (particles, fracture, fluidity, bulk density) on the properties of finite additive samples is evaluated. The impact of melting parameters on the porosity of additive samples has been studied.

Comparative analysis of technological properties and microstructure of titanium powders of different classes of alloys

The results of a study of the technological properties of titanium powders of pseudo-α and pseudo-β alloys are presented. A comparative analysis of the characteristics of powder materials obtained by centrifugal spraying has been carried out. The results of the granulometric composition of the powders were obtained, and the calculation of the spatial packing of particles was applied within the framework of the hard sphere model for various fractional compositions. To compare the microstructure and mechanical properties, test samples from pseudo-α and pseudo-β titanium alloys were obtained using the hot isostatic pressing method according to selected modes.

Ремонт деталей авіаційних двигунів із жароміцних нікелевих сплавів із застосуванням адитивних плазмових технологій

In order to improve the maintainability of aircraft engine parts, the article examined the use of additive technologies in repairs. The article establishes that the use of additive technologies by the method of plasma surfacing in the repair of aircraft engine parts, such as turbine blades, sealing discs, NA parts, is very promising and will significantly increase the percentage of parts and assemblies restored after operation, which have a significant area of damage. Turbine blades are made of nickel heat-resistant alloys with a polycrystalline structure (ЖС6К-ВИ, ЖС6У-ВИ), or from alloys with directional crystallization (ЖС32-ВИ, ЖС26-ВИ). After operating for more than 6 thousand hours, in addition to the operational wear of the ends and side walls of the shroud flanges, thermal fatigue cracks up to 6 mm deep are observed on the blades received for repair. The technology of argon-arc surfacing and the surfacing materials existing for this process do not provide the heat-resistant properties of the restored surface necessary for the operation of the blades. The solution to the problem was achieved through the use of a compressed arc source with precision adjustment of the welding current and mechanization of the supply of filler material (powder), which would make it possible to surfacing with a limited penetration depth and, accordingly, mixing the deposited material with the base metal. The developed technology made it possible to restore damaged sections of blades after operation (shroud flanges, labyrinth scallops, z-shaped profiles and airfoil ends) on heat-resistant alloys using filler material equal to the strength of the base metal. For this process, powders of nickel and cobalt alloys with a fraction of +63...-160 microns are used, obtained by atomization with a jet of inert gas (argon). The main powders used are ЖС32-ВИ, ЖС6К-ВИ, В3К, Stellite 12, Stellite 6, ХТН61. Disc material – ЭП742-ИД. Working medium, air, oil and combustion products. The maximum heating temperature of labyrinth scallops is up to 680 ºC at a maximum medium pressure of up to 1.47 MPa. The maximum peripheral speed of the scallop end is 251 m/s. Material of seal mating parts ЭИ435 (cell δ = 0,1 mm). When developing the technology, the successful experience of restoring labyrinthine scallops of turbine blades was taken into account. The restoration of the labyrinthine ridges of the disk was carried out using a compressed arc source with precision control of the welding current and a robotic installation, which included a robot for moving the plasma torch and a manipulator for rotating the disk. This made it possible to carry out surfacing with a limited penetration depth and obtain a uniformly directed bead over the entire diameter of the disk. Testing of the restored disk in order to verify its performance was carried out as part of a run-in aircraft engine. To do this, after the next assembly of the run-in engine, the disk was installed in the MPT rotor. The test was carried out in 5 cycles, the duration of each cycle was 15 hours. No wear of the labyrinth ridges or cracks was detected. The functionality of the restored disk has been confirmed. NA parts are made of heat-resistant, low-aging, high-chromium nickel-based alloy ЭП648-ВИ. They operate in hot engine conditions at temperatures up to 900'C. As a result of operation, both end surfaces and flat surfaces in the tract area are subject to wear. To restore parts of the NA, the technology of additive growth by the method of microplasma powder surfacing was used. To confirm the operability of restored parts, a set of studies of samples grown using the same repair technology was conducted. At the same time, it was established that the chemical composition of the deposited metal corresponds to the requirements of the technical conditions-» the microstructure of the deposited metal after heat treatment corresponds to the normal heat-treated state of the alloy ЭП648-ВИ (ХН50ВМТЮБ-ВИ), the level of mechanical properties of the grown alloy with subsequent serial heat treatment (aging at 700ºC, exposure -16 hours) is not lower than the forging level used in serial production of the part.

Preparation and excellent mechanical properties of nanocrystalline GW103K Mg alloy by HDDR technology

Grain size of GW103K Mg alloy powder were markedly refined to about 45 nm from 20 μm by an optimized hydrogenation-disproportionation-desorption-recombination (HDDR) process. By changing temperature, hydrogen pressure and time, the optimum hydrogenation conditions are explored by orthogonal design. Then the complete dehydrogenation process was determined by using single factor control variables. Furtherly, the HDDRed powder was spark plasma sintering (SPS) sintered and hot extruded to prepare GW103K alloy bulk. XRD, OM, scanning electron microscopy (SEM), and transmission electron microscope (TEM) were used to analyze the phase transformation and microstructure evolution, based on which the grain refining mechanism during the HDDR were discussed. The optimum HDDR parameters for preparing nanocrystalline Mg alloy powders are hydriding at 550 °C under 5 MPa hydrogen pressure for 24 h and dehydriding at 550 °C for 8 h in vacuum. The nanocrystalline GW103 alloy presents a notable dimensional stability and the grain size of the alloy bulk is 43 nm after SPS and hot extrusion. As a result, the nanocrystalline GW103K specimens exhibit excellent mechanical properties compared to the coarse-grained counterparts. Especially, the nanocrystalline GW103K alloy has a tensile elongation of 21.1% which is much more than those of the as-cast and as-extrusion alloys.

Optimization of Laser Cladding Process Parameters and Analysis of Organizational Properties of Mixer Liners.

Aiming to address the wear and replacement inconvenience of concrete mixer liners, this study utilizes a laser cladding system to clad Fe60 alloy powder on the liner. It investigates the influence of different process parameters on the forming quality of the Fe60 alloy powder cladding layer. The optimal process parameters were obtained by weighted comprehensive evaluation, and single-layer multi-pass cladding experiments were carried out under the optimal process parameters to investigate the effects of a 30%, 40%, and 50% lap rate on the surface flatness and forming quality of the cladding layer. Using a metallographic microscope, a scanning electron microscope analysis of the macro morphology and microstructure of the cladding layer was conducted, a DPT-5 penetration flaw detector was used to observe the cracks on the surface of the multi-channel cladding, a microhardness tester and friction and wear experimental machine were used for the hardness of the cladding layer, and an abrasive wear resistance test was conducted. The results show that under the process parameters of a laser power of 900 W, powder feeding speed of 7 g/min, scanning speed of 600 mm/min, and 50% lap rate, the average microhardness of the fused cladding layer reaches 742 HV, which is 1.8 times higher than that of the liner plate, and the coefficient of friction is 0.57, which improves the liner plate's wear resistance performance and service life.

Microstructure, hardness and wear resistance of plasma-sprayed and electron beam remelted Ni-Cr-Re coatings on Inconel 625

This paper presents research on the microstructure as well as mechanical properties of electron remelting of air plasma spraying (ASP) layers made of Ni-Cr-Re alloy with varying amounts of rhenium on Inconel 625. Initially, Ni-20 %Cr powder alloys with 10, 20 and 30 % (by weight) rhenium content were prepared and applied to the Inconel by ASP. Then, the air plasma sprayed coatings were remelted by electron beam under different parameters. The remelting by electron beam improved the density and smoothness of the ASP coatings. The remelted coatings were characterized by a dendritic microstructure. Wear tests revealed that the sprayed and electron-remelted coatings had a lower weight loss for higher Re content and that the hardness the remelted coating increased with increasing Re content.

Microstructural Evolution and High‐Temperature Tensile Properties of 15Cr‐Reduced Activation Ferritic Steel Processed by Hot Powder Forging of Mechanically Alloyed Powders

Reduced activation ferritic steels are being explored as possible cladding tube materials for nuclear reactors because of their low activation and excellent irradiation resistance. In the current investigation, reduced activation ferritic steel (Fe–15Cr–2W) is processed by mechanical alloying of elemental powders followed by hot powder forging. Mechanical alloying is carried out in a Simoloyer attritor mill (Zoz GmbH), after which the powders are placed in a mild steel can and forged at 1200 °C in H2 atmosphere. X‐ray diffraction and transmission electron microscopy (TEM) investigation reveal that 10 h of mechanical alloying is required to achieve complete dissolution of Cr and W in the Fe matrix powder. The relative density and hardness distribution of the forged slab is evaluated in longitudinal as well as transverse direction to optimize the powder forging operation. Electron backscatter diffraction analysis showed dynamic recrystallization to take place during the course of hot powder forging. Tensile tests are performed at room temperature as well as at elevated temperatures (600 and 700 °C). The yield strength and ultimate tensile strength at room temperature as well as at elevated temperatures are found to be higher than those reported in literature for reduced activation ferritic steels consolidated by other techniques.

Review of Laser Powder Bed Fusion’s Microstructure and Mechanical Characteristics for Al-Ce Alloys

As a new alloy manufacturing method that can break through the limitations of molds to manufacture fine parts, laser powder bed fusion has recently become a common process for producing aluminum alloys. In the fields of aerospace or automotive, aluminum alloys with both good printability and good mechanical performance in high-temperature conditions are greatly demanded, and the Al-Ce alloy is one of the alloys with significant potential. Therefore, systematic research on the additive manufacturing of Al-Ce alloys is still being explored. Herein, we review the recent progress and current status of laser powder bed fusion-produced Al-Ce alloys, giving our opinions on the development of this alloy system. Element composition, alloy powders, laser powder bed fusion parameters, microstructures, and mechanical properties at room temperature and high temperatures are summarized. The choice of alloying strategies is crucial for a specific mechanical improvement of the Al-Ce alloys. Finally, the details of the Al-Ce alloys manufactured via laser powder bed fusion are presented.

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.

Ti-Ta-Cu Biocompatible Alloy System Development via Selective Laser Melting for Prosthetic Applications

This study investigated the development of Ti-Ta-Cu alloys via selective laser melting (SLM) for potential prosthetic applications. Ti-Ta-Cu alloys with 10, 15, and 20 wt.% Ta were fabricated using in situ alloying of elemental powders. We examined the effects of Ta content and SLM processing parameters on microstructure, phase composition, mechanical properties, and corrosion resistance. X-ray diffraction analysis revealed an increase in β-phase content with increasing Ta concentration. Microstructural analysis showed a dendritic structure in Ta-rich areas, with remelting strategies improving chemical homogeneity and Ta dissolution. The Ti-20Ta-5Cu alloy exhibited the best balance of strength and ductility, with an ultimate tensile strength of 1011 MPa and elongation of 5.7%. All compositions demonstrated lower elastic moduli (103–109 GPa) compared to traditional titanium alloys. Microhardness values were highest for Ti-15Ta-5Cu, ranging from 359 to 410 HV0.5 depending on SLM parameters. Corrosion testing in Hank’s solution showed improved pitting resistance for Ti-15Ta-5Cu and Ti-20Ta-5Cu compared to Ti-10Ta-5Cu. The study demonstrates the feasibility of producing Ti-Ta-Cu alloys with tailored properties via SLM, offering potential for customized prosthetic applications with improved biomechanical compatibility and functionality.

Mechanical energy absorption capacity of the porous Ti-6Al-4V alloy under quasi-static and dynamic compression

Porous materials are very efficient in absorbing mechanical energy in different applications. In the present study, porous materials based on the Ti-6(wt.%)Al-4V alloy were manufactured with the use of two different powder metallurgy methods: i) blended elemental powder approach using titanium hydride (TiH2) as well as V-Al master alloy powders and ii) using hydrogenated Ti-6-4 pre-alloyed powder. The powder compacts were sintered with additions of ammonium bicarbonate as a pore-holding removable agent. The emission of hydrogen from hydrogenated powders on vacuum sintering and the resulting shrinkage of powder particles permitted the control of the sintering process and creation of anticipated porous structures. Mechanical characteristics were evaluated under quasi-static and dynamic compressive loading conditions. Dynamic compression tests were performed using the direct impact Hopkinson pressure bar technique. All investigations aimed at characterizing the mechanical energy-absorbing ability of the obtained porous structures. The anticipated strength, plasticity, and energy-absorbing characteristics of porous Ti-6-4 material were evaluated, and the possibilities of their application were also discussed. Based on the obtained results, it was found that porous Ti-6-4 material produced with a blended elemental powder approach showed more promising energy absorption properties in comparison with pre-alloyed powder.

Fabrication of Oxide Dispersion Strengthened Copper Alloy Powders by Atmosphere-Controlled Gas Atomization

Fabrication of Oxide Dispersion Strengthened Copper Alloy Powders by Atmosphere-Controlled Gas Atomization

Transient Liquid Phase Bonding of ZGH451 Superalloy Fabricated by Directed Energy Deposition

ZGH451, a directionally solidified Ni‐based superalloy designed for additive manufacturing, has garnered significant attention in the realm of next‐generation turbine blades. Welding the ZGH451 superalloy is crucial for promoting its practical application. In this study, transient liquid phase (TLP) bonding is applied to weld ZGH451 superalloy produced through directed energy deposition. A Ni‐based interlayer alloy powder is developed and prepared via thermodynamic calculation, with the interlayer subsequently characterized using differential thermal analysis. TLP bonding is conducted at 1200 °C for 4 h. The influence of the preset gap on the joint microstructure and mechanical properties is examined. The microstructure of the TLP bonding joints comprises athermally solidified zones (ASZ), isothermally solidified zones, and diffusion‐affected zones. The ASZ width significantly increases with the growing preset gap. A preset gap not exceeding 100 μm enables complete isothermal solidification of the joints. Particularly, joints with a preset gap ranging from 0 to 30 μm demonstrate optimal reliability, exhibiting a tensile strength of up to 1375 MPa at room temperature, which is 12% higher than the room temperature strength of the base metal (BM), and a tensile strength of 983 MPa at 760 °C, surpassing 86% of the BM's strength at the same temperature.

Development of Cost-Effective Sn-Free Al-Bi-Fe Alloys for Efficient Onboard Hydrogen Production through Al–Water Reaction

Leveraging the liquid-phase immiscibility effect and phase diagram calculations, a sequence of alloy powders with varying Fe content was designed and fabricated utilizing the gas atomization method. Microstructural characterizations, employing SEM, EDS, and XRD analyses, revealed the successful formation of an incomplete shell on the surfaces of Al-Bi-Fe powders, obviating the need for Sn doping. This study systematically investigated the microstructure, hydrolysis performance, and hydrolysis process of these alloys in deionized water. Notably, Al-10Bi-7Fe exhibited the highest hydrogen production, reaching 961.0 NmL/g, while Al-10Bi-10Fe demonstrated the peak conversion rate at 92.99%. The hydrolysis activation energy of each Al-Bi-Fe alloy powder was calculated using the Arrhenius equation, indicating that a reduction in activation energy was achieved through Fe doping.

Synthesis and Characterization of Ti-13Ta-6Sn Foams Produced Using Mechanical Alloying, the Space Holder Method and Plasma-Assisted Sintering

Highly porous titanium foams are great candidates for replacing bone structures with a low elastic modulus owing to their ability to avoid the stress shielding effect. However, the production of highly porous foams (>70 vol.%) with well-distributed, stable, and predictable porous architectures using powder compaction and space holders is challenging. In this study, pure titanium powder and mechanically alloyed Ti-13Ta-6Sn were mixed with 50, 70, and 80 vol.% KCl powders as a space holder, cold-compacted, and sintered in a plasma-assisted sintering reactor to produce highly porous foams. The space holder was completely removed using heat and plasma species collisions prior to sintering. A Ti-13Ta-6Sn alloy powder with α, β, and metastable FCC-γ phases was synthesized. The characteristics of the alloyed powder, mixing step, and the resulting sintered samples were compared to those of CP-Ti. After sintering, the alloy exhibited α and β phases and a reduced elastic modulus. Foams with an elastic modulus in the range of the cortical and trabecular bones were obtained. The results showed the effects of the space holder volume fractions on the volume fraction, size, distribution, interconnectivity, and shape of the pores. The Ti-13Ta-6Sn foams exhibited a uniform open-celled porous architecture, lower elastic modulus, higher yield strength, and higher passivation resistance than CP-Ti. Ti-13Ta-6Sn exhibited a nontoxic effect for the mouse fibroblast cell line.