Papers by Keyword: Gas Atomization

Abstract: It is shown experimentally and numerically that quenching (Melt Quenching - MQ) of REM-containing (up to 40 wt.%) Fe-B-Nd melt by inert gas flow (Gas Atomisation Method - GAP) in NH3-containing atmosphere makes it possible to obtain spherical particles with a given fractional and chemical composition and characterised by increased corrosion resistance. The applicability of the obtained particles in the traditional powder technology for the formation of anisotropic and isotropic sintered magnets is established. It is shown that MQ GAP can regulate the functional properties of sintered magnets by mixing different chemical and fractional compositions. It is shown that heat treatment of MQ GAP powders improves their magnetic hysteresis properties and magnetoplasts made from them. The applicability of the obtained MQ GAP REM-containing particles for cladding technologies and additive processes is proved. Hybrid laser & micro-casting surfacing technology for additive processes of processing Fe-Nd-B ternary and MQ GAP alloys into micromagnets - 'Hybrid laser & micro-casting technology for surfacing in additive processes' is proposed. The possibility of realising the described technology for other MQ GAP REM containing alloys with multicomponent low melting eutectic in the intergranular space capable of amorphising at cooling rates of 10³÷10⁵ K/s has been shown.

Abstract: The purpose of this research is to identify the optimal condition of the wire arc spray technique equipped with the gas atomization system using central composite design (CCD) of response surface methodology (RSM) in Minitab 18 software. Two independent parameters of the wire arc spray technique were studied, including arc voltage and air pressure. The statistical evaluations showed that both arc voltage and air pressure parameters had effects on the quality of the powder in terms of particle morphology and particle size distribution. Additionally, the arc voltage had the highest effect on particle circularity, whereas air pressure had the highest effect on particle size distribution. Finally, the optimal condition was the arc voltage and air pressure of 36.7429V and 0.5436 MPa, respectively, achieving a maximum particle circularity of 0.8284 and a targeted particle size distribution of 45 μm with the desirability of 0.7566 and 0.9928, respectively.

Abstract: Powders of X6CrNiTi18-10 stainless steel were fabricated from original workpieces of different grade by gas atomization method. It was found that it is necessary to use argon as a gas for gas atomization of X6CrNiTi18-10 steel, since the use of nitrogen leads to the formation of its compounds, namely, titanium nitride. It is shown that all used workpieces – electric arc, electric slag and vacuum arc refinement – allow one to obtain powders suitable for further utilization in selective laser melting technology of 3D printing. The main physicochemical and technological properties of the obtained powders have been investigated. Changes in the chemical composition and quality of the powders are not significant within the X6CrNiTi18-10 grade. The 0...20 μm fraction of powders does not have fluidity, and thus cannot be used for additive technologies. The fraction 20...63 μm have suitable rheological properties for additive technologies and may be used in selective laser melting (SLM) process. The yield of target fraction 20 ... 63 microns was ≈45%. The fraction 63...120 μm may be used for the direct metal deposition (DMD) additive technology. Considering the economic aspect of the technology, it is preferable to use original workpieces of X6CrNiTi18-10 steel produced by electric arc or electroslag process, since the market price of vacuum arc steel is significantly higher. The fraction of ferrite phase in the powder increases with a decrease of particle size of the resulting powder and is lower comparing to the original workpiece. In the future, for a detailed study of the technological properties, it is planned to grow samples from each type of the obtained powders on installation for selective laser melting and direct laser deposition to determine the physical and mechanical properties of fabricated samples (tensile and impact bending tests) and carry out metallographic studies.

Abstract: Rina Consulting Centro Sviluppo Materiali (CSM) has been involved in the study and development of powder metallurgy for different applications, thanks to its participation in many research industrial and funded projects. The entire metal powder production chain takes place within the company's own researcher and facilities. This allows to produce high quality powders starting from alloy design, VIGA atomization and chemical, rheological and particle size analysis. In recent years, the development has mainly concerned manufacturing processes. Currently only a limited number of metal alloys can be processed by AM. For that reason, the alloy design becomes a really important topic to enlarge AM capabilities to other materials and applications. Starting from commercial Thermodynamic and Kinetic codes and proprietary models on solidification and micro-segregation, the alloy chemical composition can be fine-tuned to optimize the microstructure, considering the target properties of the material and the relevant AM processing windows, taking into account also the post process treatment conditions. Moreover, the knowledge of the production plants allows CSM to have a wide vision on the realization and the characterization of the metal powders focusing to achieve the best powder quality suitable for AM applications. Finally, AM is a relatively “new” process, standardization is still an ongoing activity involving several communities and organizations like ASTM, AWS and ISO; in this contest CSM has already designed the guidelines for qualification and certification processes and has created a dedicated laboratory to qualify powders of AM players.

Abstract: This work investigates the evolution of the microstructure of an Nb-23Ti-20Si (at.%) based alloy, from the primary plasma-melted material that is gas-atomized towards the consolidated material (here using SPS). The nature, morphology and size of the solid solution and the various silicides are followed by SEM, EDS and EBSD. Homogenous and fine microstructures are obtained after the SPS step and are improved by a subsequent heat treatment (1500°C, 100 h). However blocky silicides, already present in the powder particles, cannot be eliminated. A better control of the primary material’s microstructure would improve the microstructure of the final material.

Abstract: Gas atomization is one of the most cost-effective methods for preparing spherical powders. The Cu-9.7Sn-0.2P alloy powder for 3D printing was prepared by a self-developed double nozzle gas atomization technique with different deliver tube diameters, and the particle size and shape of the powder were characterized. Results show that the powder particles are mostly nearly spherical, mixed with a few irregular powders. The average O. Bluntness of the powders are 60~70%, the average Outgrowths are lower than 18%. The deliver tube diameter affects the powder characteristics directly. The increase of the diameter increases the particle size of the powder and reduces the sphericity. At the same time, the adhesion of the satellite powder decreases, the flowability becomes better and the oxygen content drop. The surface and internal structure of the powder are mainly cellular and dendritic structures.

Abstract: Pre-alloyed gamma titanium aluminide powders were fabricated by argon gas atomization. The powder was hot isostatic pressed (HIP) at 1200°Cand 150MPa for 3h to obtain full density compact. The properties of the powders and the HIP’ed compacts were investigated in this work. The microstructure of the powder exhibited dendrite and cellular mixed image, resulted from rapid solidification and independent of particle size. The microstructural transition from cell to dendrite could be readily represented in a droplet or the droplets of different size. The transition was the result of the decrease of undercooling. XRD analysis result showed that the powder consisted of α₂ phase and γ phase, coarse powder was mostly γ phase, while fine powder mostly α₂ phase. After HIP, the near gamma microstructure showed an average γ-TiAl grains of approximately 6μm.

Abstract: Metallic composite materials are mainly manufactured by powder metallurgy (PM) or casting, with reinforced ceramic particulates dispersed in a metal matrix. The current study presents an investigation with respect to simultaneously gas-atomized spherical Ti/TiC composite powders. Various analytical methods are used to characterize the gas-atomized Ti/TiC composite powders, including XRD, laser particle size analysis, flow rate tests, apparent density and tap density tests, SEM, and alike. The spherical Ti/TiC composite powders will be further laser sintered at the next stage to utilize mechanical properties testing.

Abstract: In this study, we fabricated spherical Ti-6Al-4V powders using gas atomization. Scanning electron microscope, optical microscope, X-ray diffraction and particle size distribution were extensively performed to investigate the properties of gas-atomized Ti-6Al-4V powders. The XRD analysis shows all the gas-atomized powders are with both α and β phases. The surface of coarse powders exhibited cellular structure with equiaxed grains. However, the fine powders achieved smooth surfaces and could not be observed any crystallization. Attributed to rapid solidification, both α cell and needle-like martensite α’ phase were observed in the internal area of coarse powders, while only honeycomb cellular structure was demonstrated with refined grains in fine powders.

Abstract: In this work, Cu₅₀Zr₄₃Al₇ metallic glass powders were produced by gas atomization method. The structure and crystallization characteristics of the as-prepared powders with different particle size distributions were studied in detail. The amorphous state of the alloy powders was confirmed by X-ray diffraction (XRD), in which amorphous phase formed. The scanning election microscopy (SEM) result showed that the selected metallic glass powder performed excellent owned good spherical morphology, which was also observed on an optical microscope (OM). At the same time, the particle size distributions ranging from 20 μm to 200 μm of as-prepared metallic glass powders were determined by laser diffraction. Moreover, the crystallization behavior of the Cu₅₀Zr₄₃Al₇ metallic glass powders was investigated by differential scanning calorimetry (DSC).