Gas Atomization Method Research Articles

Properties of Al0.5CoCrFeNi2Ti High-Entropy Alloy System: From Gas-Atomized Powders to Atmospheric Plasma-Sprayed Coatings

AbstractThe performance of the Al0.5CoCrFeNi2Ti HEA atmospheric plasma-sprayed coating was extended from characterizing the properties of its powder prepared via the gas atomization method. It was observed that the gas-atomized HEA powders possessed a solid solution BCC phase, while a major phase transformation to a FCC-L21 intermetallic phase occurred during the annealing process. The formation of the intermetallic phase resulted in an increase in average hardness from 6.28 to 7.64 GPa after annealing at 900 °C for 1 h. Afterward, HEA powders were applied in the atmospheric plasma spray technology. The phase constitution of Al0.5CoCrFeNi2Ti HEA coatings was investigated by varying powder size and applied current. It was observed that the smaller powder sizes prone to oxidation, whereas higher applied current facilitated the phase transformation from BCC to FCC phase. The nanoindentation test indicated distinct average microhardness values for the interlamellar oxide region, BCC unmelted particle and FCC phase lamellar region, which was measured at 12.35, 8.68 and 5.97 GPa, respectively. As a result, the adjustability of coating hardness was achieved by manipulating the relative phase ratio.

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.

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.

A Comparative Study of Machining Property in Inconel 718 Superalloy Grinding with Al2O3- and CBN/Fe-Based Spherical Magnetic Abrasives

A comparative analysis was studied on the finishing performance of spherical CBN/Fe-based magnetic abrasive particles (MAPs) and Al2O3/Fe-based magnetic abrasive particles (MAPs) prepared by the gas atomization method in the magnetic abrasive finishing (MAF) of the Inconel 718 superalloy. In the MAF, it was found that compared with Al2O3/Fe-based MAPs, CBN/Fe-based MAPs have a lower grinding temperature and generate less heat during the grinding of the Inconel 718 superalloy. The grinding pressure generated on the workpiece is relatively stable (Al2O3/Fe-based MAPs have a larger fluctuation range of grinding pressure on the workpiece surface during the grinding process). The surface roughness of the workpiece rapidly drops from Ra 0.57 μm to Ra 0.039 μm, and the material removal reaches 42 mg within 20 min. After finishing, the scratches on the surface of the workpiece basically disappear, the contour curve is relatively flat, and there is almost no adhesion on the surface of the workpiece. The mirror effect of the superalloy surface is good, and ultimately a better surface quality can be obtained.

High activity retention Al–Bi–Zn-base composite powder with mild hydrogen generation

Al–10Bi–7Zn and Al–10Bi–7Zn–1.5X (X: Cu, Fe, Ni, in wt.%) composite powders were designed and prepared through phase diagram calculation and gas atomization method. The effects of Cu, Fe, and Ni on the hydrolysis of Al–Bi–Zn-base composite powders for hydrogen production were investigated respectively. The composition and morphology of powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy disperse spectroscopy (EDS) analyses. Hydrolysis performance test results indicate that the additions of Cu, Fe, or Ni can modify the hydrogen production rate and enhance oxidation resistance in Al–10Bi–7Zn ternary alloy composite powder. In the quaternary composite powder system, Al–10Bi–7Zn–1.5Ni (wt.%) exhibits the best performance with the hydrogen generation yield of 75.3% (954.1 mL/g) within 500 min when reacting with distilled water at 60 °C and maintains a hydrogen yield of 57.9% (733.7 mL/g) within 1500 min after being stored (30 °C, relative humidity of 60%) for 7 d. In addition, the mechanism investigation suggested that the additions of Cu, Fe, or Ni in Al–Bi–Zn-base composite powders can stabilize the Al matrix to retain the high activity of powders resulting from inhibiting the cracking of composite powders in the air.

Ultra strong FCC structured Ni8Cr4Co4Fe6W2 high entropy alloys with high strength and ductility by laser powder bed fusion

The high entropy alloys (HEAs) are widely used in high temperature service environment (such as aviation engine blades) with bright application potential in additive manufacturing. Laser powder bed fusion (LPBF) is technology currently offers the best reproducibility and dimensional accuracy for part production. The unique atomic lattice structure of HEA makes its plastic deformation mechanism different from that of traditional dilution alloy, resulting in the strengthening effect of face-centered cubic high-entropy alloy different from that of traditional metal alloy materials. In this paper, Ni8Cr4Co4Fe6W2 was designed by means of composition control. Its spherical powders with uniform composition were successfully prepared by high temperature remelting spheroidization (PHTR) method, compared with gas atomization (GA) method. The strain rate sensitivity m values of GA-Selective Laser Melting and PHTR-Selective Laser Melting samples were 0.030 and 0.027, respectively. The hardness of Ni8Cr4Co4Fe6W2 high-entropy alloy showed a trend of continuous increase with the decrease of grain size, while the elastic modulus didn’t change much (PHTR-SLM is 193 Gpa and GA-SLM is 189 Gpa). The simulated value of the contact stress decreased by 23 % compared with the theoretical value. The contact radius increased with the increase of plastic deformation in addition to the reduction of contact pressure. The printing sample value of the elongation, yield strength (YS) and Ultimate Tensile Strength (UTS) on PHTR-SLM has increased by 39.6 %, 33.7 % and 25.9 %, respectively in additive manufacturing, compared to GA-SLM. The ability to produce refractory HEAs through PHTR method will make it possible to manufacture complex geometry shapes at a reasonable cost.

High strength and ductility on Ni6W2Cr4Fe8Ti1 high entropy alloys by selective laser melting

High entropy alloys (HEAs) have a good application potential in the preparation of high temperature service parts with complex shapes in additive manufacturing. Powder bed fusion (PBF) is a prominent type of additive manufacturing process that utilizes the thermal energy to bind powder materials together to build up plastic or metallic parts. However, the traditional gas atomization method (GA) often produce alloy powder (containing refractory element) with uneven composition, affecting the quality and performance of specimens. That is why innovative or opposite classical production powder methods are in demand for the PBF. It is worth noting that mechanical alloying technology overcomes the limitation of high temperature alloying of HEA containing refractory elements and realizes solid alloying of insoluble elements. In this paper, high entropy alloy Ni6W2Cr4Fe8Ti1 containing refractory elements is designed by means of composition control. Its spherical powders with uniform composition were successfully prepared by the new mechanical alloying - high temperature remelting spheroidization dual process (DP) method. The treated powder composition is evenly distributed with particle sizes ranging from 15 to 28 μm. And the spheroidization rate has exceeded 98.23% at 1943 K. The sample value of YS and UTS on Ni6W2Cr4Fe8Ti1 (DP-SLM) has increased by 35.7%, 45.5% and 27.3%, respectively in additive manufacturing, compared to GA-SLM. The ability to produce refractory HEA through DP method will make it possible to manufacture complex geometry shapes at a reasonable cost. It offers theoretical guidance to manufacture fine grain materials with high strength and ductility of new HEA components.

Study on Flowability Regulation of Vacuum Gas-Atomized Fe-Cr-Ni-W-B Spherical Powder.

High-quality Fe-Cr-Ni-W-B spherical powder is crucial for the powder metallurgy preparation of high-strength and tough Fe-Cr-Ni-W-B alloys. In this study, the controlled preparation of high-quality Fe-Cr-Ni-W-B spherical powder was achieved using the vacuum gas atomization method. The effects and mechanisms of atomization gas pressure, the melt nozzle inner diameter, and heat treatment temperature on the microstructure and flowability of Fe-Cr-Ni-W-B spherical powder were systematically investigated. By optimizing process parameters, spherical Fe-Cr-Ni-W-B powder with a sphericity of 95.1% and a flowability of 15.88 s/50 g was obtained, laying the foundation for the powder metallurgy preparation of high-strength and tough Fe-Cr-Ni-W-B alloys.

Enhancement effect of Li addition on nitriding reaction and combustion of Al-Li alloy in N2

For aluminum-based alloy particles, the addition of alloying element lithium (Li) with the properties of a high chemical activity and a low melting/boiling point can significantly improve the thermo-reactive properties of aluminum (Al) particles. To further reveal the combustion mechanism, this paper presents the nitriding reaction and combustion characteristics of Al-Li alloy in nitrogen (N2) through thermogravimetric analysis and differential scanning calorimetry (TG-DSC) analysis at a low heating rate and laser-induced ignition experiments at a high heating rate, considering the influences of two kinds of Li contents (1.0 wt% @ Al-1.0Li and 2.5 wt% @ Al-2.5Li) on these characteristics and making a comparison to the counterpart Al. Al-Li alloy powders as-prepared by gas atomization method showed the texture of the Li-rich eutectic phase compounds on the surface by scanning electron microscope (SEM) characterization. The TG-DSC results demonstrated that the thermal nitriding reaction of Al-Li alloy in N2 was significantly faster than that of pure Al. The nitriding reaction temperature decreased from 853 °C for pure Al to 245 °C for Al-2.5Li alloy with a reduction of 71 %. The final weight gain of Al-2.5Li alloy was almost three times higher than that of pure Al in N2. The SEM photograph of intermediate nitriding products revealed that the cracks and loose “island” structures in the Li-rich zone on the Al-Li surface were the key to preventing the formation of a “passivation effect” into Al and promoting N2 uptake during melting. In addition, Li also acts as a catalytic carrier and “oxygen absorber” to enhance the Al-N reaction. The combustion of single Al-Li alloy microparticles induced by laser showed two stages: preheating and rapid nitriding. Al-Li alloy particles were ignited more rapidly and showed typical gas-phase / surface combustion modes different from pure Al. According to these findings, the combustion mechanism was proposed to help guide the development of Al-based solid propellants containing Li and the synthesis of AlN/Al composites in nitrogen-rich environments.

Innovative Method for the Mass Preparation of α″-Fe16N2 Powders via Gas Atomization

The iron nitride materials, especially α″-Fe16N2, are considered one of the most promising candidates for future rare-earth-free magnets. However, the mass production of α″-Fe16N2 powders as a raw material for permanent magnets is still challenging. In this work, starting from iron lumps as a raw material, we have managed to prepare the α″-Fe16N2 powders via the gas atomization method, followed by subsequent nitriding in an ammonia–hydrogen gas mixture stream. The particle size was controlled by changing the gas atomization preparation conditions. X-ray diffractograms (XRD) analyses show that the prepared powders are composed of α″-Fe16N2 and α-Fe phases. The α″-Fe16N2 volume ratio increases with decreasing powder size and increasing nitriding time, reaching a maximum of 57% α″-Fe16N2 phase in powders with size below 32 ± 3 μm after 96 h nitridation. The saturation magnetization reaches the value of 237 emu/g and a reasonable coercivity value of 884 Oe. Compared to the saturation magnetization values of α-Fe powders, the α″-Fe16N2 powders prepared through our proposed approach show an increase of up to 10% in saturation and demonstrate the possibility of mass production of α″-Fe16N2 powders as precursors of permanent magnets without rare earths.

A thermodynamic approach for preparing oxide dispersion–strengthened Ti-6Al-4V powder by in situ gas atomization method

This study examined the feasibility of in situ fabrication of oxide dispersion–strengthened (ODS) Ti-6Al-4V (Ti64) powder through a gas atomization (GA) method. Thermodynamic calculations were performed to design the ODS Ti64 by deriving compositions of yttrium oxide (Y2O3), which is completely dissolved into the molten Ti64 and subsequently reprecipitated during cooling in the GA process. In addition, the changes in the equilibrium phase fractions based on varying the Y2O3 content and oxygen (O) concentration in the Ti64 matrix were investigated. From the thermodynamic calculations, an optimal composition for the ODS Ti64 alloy was determined, involving the addition of 1 wt% Y2O3 to Ti64 with an O concentration of 0.1 wt%. The alloy ingot was prepared via vacuum arc remelting, leading to the precipitation of coarse Y2O3 along grain boundaries because of a slow cooling rate. The ODS Ti64 powder was fabricated through an electrode induction melting GA method, and the resulting ODS Ti64 powder had spherical morphology, with uniformly distributed Y2O3 particles of several tens of nanometers in size. The hardness of a conventional Ti64 powder was 354 HV, significantly increasing to 485 HV in the ODS Ti64 powder due to the Y2O3 nanoparticles’ dispersion. This study introduces a novel methodology for fabricating high-quality ODS Ti64 powder by the in situ GA method.

The Influence of Preparation Parameters on the Morphology and Magnetic Properties of Fe-N Powders Obtained by the Gas Atomization Method

α″-Fe16N2 materials are of increasing interest for their applications in products such as rare earth-free permanent magnets. The lack of a method of mass production for powders as raw materials delays the preparation of such magnets. Through employing the gas atomization method, we managed to prepare α″-Fe16N2 powders whose morphology and magnetic properties were tailored by the preparation parameters. As a result of optimizing the preparation parameters (ejection temperature and pressure, ejection nozzle diameter, and atomization pressure), we managed to prepare powders with a size of about 30 μm and a content of 31% α″-Fe16N2 phase. The value of the saturation magnetization (234.8 emu/g), the reasonable coercivity value (970 Oe) presented by the prepared powders, and the opportunity of scaling up approaches based on the preparation of powders via gas atomization support the feasibility of preparing α″-Fe16N2 powders at an industrial level.

Densification behavior, mechanical and electrical properties of in-situ TiB2p/Cu composite powder via vacuum hot pressing

The spherical TiB2p/Cu composite powder was prepared first by in-situ reaction coupled with the gas atomization method, then the bulk TiB2p/Cu composites with diffusely distributed sub-micron TiB2p were prepared by vacuum hot pressing (VHP). The densification behavior of in-situ TiB2p/Cu composite powder compacts during sintering was investigated, indicating that the existence of TiB2p inhibits the densification. The ultimate tensile strength, conductivity and relative density of the sintered TiB2p/Cu composite are 400 MPa, 89.7% IACS and 99.7%, respectively, and the reasons for the high strength and conductivity of the composites were discussed. This work is expected to provide a technically viable solution for the preparation of high-performance TiB2p/Cu composite by VHP with in-situ composite powder.

In situ fabrication of spherical oxide dispersion strengthened Ti powder through gas atomization

Oxide dispersion strengthened (ODS) alloys exhibit excellent mechanical properties due to fine oxide dispersion, but they have great limitations due to utilizing powder fabrication via mechanical alloying. Therefore, this study examined the alloy composition and process that can fabricate ODS titanium (Ti) powder in situ through a gas atomization method. The composition and content of the oxide, which can dissolve in molten Ti during melting and precipitate inside powders during cooling in the gas atomization, were derived through thermodynamic calculations. The ODS Ti alloy composition of Ti + 1 wt% yttria (Y2O3) was derived, and the alloy was prepared as a powder through an electrode induction melting gas atomization (EIGA) method. First, rod-shaped ingots were prepared through vacuum arc remelting (VAR), and Y2O3 was coarsely precipitated along the grain boundaries due to the slow cooling rate. Then, the ODS Ti powder was fabricated by EIGA using the rod ingot and spherical powders could be continuously fabricated. The cross-section microstructure of the powder was observed, and the Y2O3 particles with several tens of nm were uniformly distributed inside the powder. These thermodynamic calculations and experiments confirmed that ODS Ti powder could be fabricated in situ using the gas atomization method.

Preparation and Microstructure of Multi-Component High Entropy Alloy Powders Fabricated by Gas Atomization Method

As an attractive high-entropy alloy, AlCrCoNiCu high-entropy alloy has excellent corrosion resistance, wear resistance, and anti-bacterial capabilities, and is considered to be a potential substitute material for marine and nuclear industry materials with great potential. One key to further optimizing the performance of high entropy alloy was to prepare high entropy alloy powder materials with uniform composition, good flow-ability, and stable performance. In this work, the AlCrCoNiCu high entropy alloy powder was prepared by the gas atomization method. The results indicated that the powder was spherical in shape, homogeneous in composition, and composed of a face-center cubic (FCC) phase. After adding Fe and Mn elements, FCC and body-center cubic (BCC) phases appeared and the particle size of the powder was mainly located at 10–50 μm. Furthermore, the larger the particle size was, the more obvious the surface roughness was. With the decreasing powder size, its shape became relatively regular, and the surface roughness decreased. This work provided an experimental and theoretical reference for preparing high-performance single-phase and multi-phase high entropy alloy spherical powders.

Preparation of In Situ Synthesis TiC/Ti6Al4V Composite Powder with Homogeneous Dispersion by Electrode Induction Gas Atomization Method

Preparation of In Situ Synthesis TiC/Ti6Al4V Composite Powder with Homogeneous Dispersion by Electrode Induction Gas Atomization Method

Effects of the Gas-Atomization Pressure and Annealing Temperature on the Microstructure and Performance of FeSiBCuNb Nanocrystalline Soft Magnetic Composites.

FeSiBCuNb powders prepared by the gas atomization method generally exhibit a wide particle size distribution and a high degree of sphericity. In addition, the correspondingly prepared nanocrystalline soft magnetic composites (NSMCs) perform good service stability. In this paper, effects of the gas-atomization pressure and annealing temperature on the microstructure and soft magnetic properties of FeSiBCuNb powders and NSMCs are investigated. The results show that the powders obtained by a higher gas-atomization pressure possess a larger amorphous ratio and a smaller average crystallite size, which contribute to the better soft magnetic performance of the NSMCs. After being annealed at 550 °C for 60 min, the NSMCs show a much better performance than those treated by the stress-relief annealing process under 300 °C, which indicates that the optimization of the soft magnetic properties resulting from the precipitation of the α-Fe(Si) nanocrystalline largely overwhelms the deterioration caused by the grain growth of the pre-existing crystals. In addition, the annealed NSMCs prepared by the powders with the gas-atomization pressure of 4 MPa show the best performance in this work, μe = 33.32 (f = 100 kHz), Hc = 73.08 A/m and Pcv = 33.242 mW/cm3 (f = 100 kHz, Bm = 20 mT, sine wave).

Influence of energy area densities on microstructure evolution and properties of laser direct energy deposited Ni-Co-Mn-Al-Y magnetic shape memory alloy

A novel Ni-Co-Mn-Al-Y magnetic shape memory alloy powder was prepared by the vacuum induction melting gas atomization method, and Ni-Co-Mn-Al-Y alloy samples were prepared by laser directed energy deposition (LDED) technique under different energy area densities and subsequent heat treatment. The effects of energy area densities and heat treatment on the grain size, microstructure, phase transformation, compressive strength, and elastocaloric response of the Ni-Co-Mn-Al-Y alloy samples prepared via LDED were clarified. The results showed that the characteristics of the prepared Ni-Co-Mn-Al-Y alloy powder met the requirements of LDED technology and the powder exhibited good laser printability. The microstructure of the samples before and after heat treatment was composed of martensite, austenite, and γ phase. The optimized energy area density sample of 150 J/mm 2 demonstrated a good comprehensive performance with a compressive strength of 1241 MPa and an adiabatic temperature change of –1.9 K. This work can provide a useful reference for preparing high-performance magnetic shape memory alloys by LDED. • A new Ni-Co-Mn-Al-Y alloy powder suitable for LDED was successfully prepared by the VIGA method. • The influence of energy area densities and heat treatment on the microstructure evolution of the prepared alloy was clarified. • The abnormal grain growth was related to the evolution of γ phase and subgrain boundaries during heat treatment. • The alloy with higher compressive strength and better adiabatic temperature change was successfully prepared.

Analysis of technological processes of production of spherical powders and granules of NiAl nickel monoaluminide for the needs of domestic engine building

The article is devoted to the study of the features of various methods for obtaining granules of nickel aluminide NiAl. The problems hindering the widespread use of nickel aluminide NiAl in modern aircraft and engine construction are analyzed. It has been revealed that the main problems hindering the widespread industrial use of nickel aluminide NiAl are practically zero plasticity of the material during pressure treatment and difficulties in machining parts made of this material. However, this problem can be solved with the use of pellet metallurgy technologies, when by sintering the granular material, an almost finished product is obtained that requires minimal amounts of subsequent machining. Within the framework of the conducted studies, the quality criteria of the obtained granules were determined, which include the sphericity of the granules, the stability of the obtained dimensions of the granular material, the absence of defects in the form of pores, the absence of satellites on the surface of the granules, the presence of a finely dispersed dendritic structure of the granule material. Several methods of obtaining granules of nickel aluminide NiAl have been investigated from the point of view of obtaining the highest quality raw materials, namely: the method of spraying the melted billet with a high-temperature inert gas flow (gas atomization method), the method of centrifugal spraying of the melted electrode (PREP method), the method of centrifugation of the melt using a perforated crucible. It is determined that the optimal way to obtain a high-quality granulate of NiAl material is the method of centrifugal spraying of the melted electrode. In the course of the conducted research, it was proved that the main parameter of the process of centrifugal spraying of the melted electrode, affecting the quality of the obtained granules, their diameter and the value of the dendritic parameter of the microstructure of the granules, is not so much the current strength I as the rotation speed of the melted electrode n. The optimal values of the electrode rotation speeds are determined, which are n ≈ 15000-16000 revolutions per minute at a current strength I ≈ 1000-1500 A. A technology for obtaining high-quality NiAl material granulate has been developed and tested, which includes operations for obtaining initial NiAl blanks by self-propagating high-temperature synthesis, subsequent remelting of semi-finished products, heat treatment, separation of granules and subsequent granulation by the PREP method.

Effect of Fe on the Hydrogen Production Properties of Al-Bi-Sn Composite Powders.

Fe additives may play an important role in the preparation of aluminum-based hydrolysis hydrogen powder, with high hydrogen yield, low cost, and good oxidation resistance. Therefore, it is necessary to ascertain the effect of Fe on the hydrogen production performance of Al-Bi-Sn composite powders. According to the calculated vertical cross-section of the Al-10Bi-7Sn-(0~6)Fe (wt.%) quasi-binary system, Al-10Bi-7Sn-xFe (x = 0, 0.5, 1.5, 3) wt.% composite powders for hydrogen production were prepared by the gas-atomization method. The results showed that the Al-10Bi-7Sn-1.5Fe (wt.%) powder exhibited an extremely fast hydrogen generation rate at 50 °C, which reached 1105 mL·g−1 in 27 min in distilled water, 1086 mL·g−1 in 15 min in 0.1 mol·L−1 NaCl solution, and 1086 mL·g−1 in 15 min in 0.1 mol·L−1 CaCl2 solution. In addition, the antioxidant properties of these powders were also investigated. The results showed that the hydrogen production performance of the Al-10Bi-7Sn-1.5Fe (wt.%) powder could retain 91% of its hydrogen production activity, even though the powder was exposed to 25 °C and 60 RH% for 72 h. The addition of Fe not only promoted the hydrogen generation rate of the Al-Bi-Sn composite powders, but also improved their oxidation resistance. The Al-10Bi-7Sn-1.5Fe (wt.%) composite powder shows great potential for mobile hydrogen source scenarios with rapid hydrogen production.