Influence Of Powder Characteristics Research Articles

Influence of Powder Characteristics on the Microstructure and Mechanical Behaviour of GH4099 Superalloy Fabricated by Electron Beam Melting

A Chinese superalloy, GH4099 (~20 vol.% γ′ phase), which can operate for long periods of time at temperatures of 1173–1273 K, was fabricated by electron beam melting (EBM). Argon gas atomized (GA) and plasma rotation electrode process (PREP) powders with similar composition and size distribution were used as raw materials for comparison. The microstructure and mechanical properties of both the as-EBMed and post-treated alloy samples were investigated. The results show that the different powder characteristics result in different build temperatures for GA and PREP samples, which are 1253 K and 1373 K, respectively. By increasing the building temperature, the EBM processing window shifts towards a higher scanning speed direction. Microstructure analysis reveals that both as-EBM samples show a similar grain width (measured to be ~200 μm), while the size of γ′ precipitated in the PREP sample (~90 nm) is larger than that of the GA sample (~130 nm) due to the higher build temperature. Fine spherical γ′ phase precipitates uniformly after heat treatment (HT). Furthermore, intergranular cracking was observed for the as-fabricated PREP sample as a result of local enrichment of Si at grain boundaries. The cracks were completely eliminated by hot isostatic pressing (HIP) and did not re-open during subsequent heat treatment (HT) of solution treatment and aging. The tensile strength of the PREP sample after HIP and HT is ~920 MPa in the building direction and ~850 MPa in the horizontal direction, comparable with that of the wrought alloy.

The influence of powder characteristics on densification behavior and microstructure evolution of W-Cr-Zr alloy consolidated by field-assisted sintering technology

In the present study, the influence of powder characteristics on the densification behavior and microstructure evolution of the W-Cr-Zr alloy during consolidation was investigated. The W-Cr-Zr alloy powders were prepared through mechanical alloying in different modes, i.e. continuous mechanical alloying (CMA) and intermittently mechanical alloying (IMA). It can be found that the IMA powders have a higher grain boundary density and homogenous microstructure, which exhibits a better sintering performance than the CMA powders. The IMA powders are capable of full densification and homogenization after sintering at low temperature (1395 °C), with the grain size approaching 284 nm. Through the characterization of antioxidant properties, it was confirmed that the alloy prepared using IMA powders has an excellent anti-oxidation performance.

Influence of powder characteristics on properties of parts manufactured by metal additive manufacturing

Influence of powder characteristics on properties of parts manufactured by metal additive manufacturing

Powder HIP of pure Nb and C-103 alloy: The influence of powder characteristics on mechanical properties

In this work, pure Nb processed by Powder Metallurgy Hot Isostatic Pressing (PM HIP) was investigated as a potential alternative to C-103 Nb-based alloy for the manufacture of near-net-shape thruster combustion chambers. Three Nb powders with varied particle size range (fine, mid-range and coarse) and C-103 powder were investigated to understand the differences in particle size distribution (PSD), morphology and oxygen (O) content present in the alloy chemistry. The as-HIPed microstructures of pure Nb and C-103 are characterised by a near to fully dense microstructure and the absence of PPBs. Microstructural analyses performed on pure Nb highlighted the influence of particle size on the average as-HIPed grain size. Additionally, it was observed that O content plays a crucial role in the microhardness of pure Nb. Tensile tests performed on Nb mid-range and on Nb mid-range sieved showed that a simple sieve operation was effective in increasing the strength of the material while maintaining good levels of elongation. Alternatively, it was also demonstrated that pure Nb powder heat treatment can be regarded as an effective way to increase the O levels in pure Nb powders as witnessed by the high hardness levels. On the other hand, as-HIPed C-103 powder showed superior tensile properties if compared to the minimum specifications for wrought C-103. Finally, to summarise, the work performed on pure Nb, a simple structure-property relation model was developed to predict the YS of pure Nb based on the O levels and grain size of the as-HIPed microstructure.

Influence of powder characteristics on microstructure and mechanical properties of Inconel 718 superalloy manufactured by direct energy deposition

This work reports a study of the differences between properties of gas atomized (GA) and plasma rotating electrode processed (PREP) Inconel 718 powder and their printed parts. Powder morphology, particle size distribution, chemical composition, flowability and density have been comprehensively analyzed. From that, it can be found the properties of PREP powder were better than GA powder. The densification, microstructure, mechanical properties, and oxidation resistance of GA and PREP samples prepared by direct energy deposition(DED) were also studied. The results showed that the perfect morphology of powder could contribute to a finer microstruture and a more obvious preferential orientation of the printed part. Moreover, the density, mechanical properties and oxidation resistance of the printed parts were all better. This work highlights that properties of powder are crucial to the properties of the printed parts, and emphasises the importance of powder morphology on energy absorption, microstructure and preferential orientation in DED process.

Rheology of dry powders and metal injection molding feedstocks formulated on their base

The influence of powder characteristics on the moldability of metal injection molding feedstock is relatively well understood, but remains difficult to quantify other than by real-scale injections. This study aims to correlate feedstock moldability performances with melt viscosity and dry powder rheology. Four stainless steel powders exhibiting different particle sizes and shapes were tested in dry conditions using an FT4 powder rheometer to obtain thirteen different powder rheology-related metrics. These powders were subsequently mixed with a wax-based binder to formulate four feedstocks that were tested in melt conditions using a rotational rheometer to characterize the injection-related rheology of the feedstock formulations. The moldability of the feedstocks was finally quantified using real-scale injections performed into a spiral mold cavity to measure the injected lengths, and the correlation between the dry and melt rheology metrics and the real-scale injection moldability was evaluated. Results showed that the feedstock melt viscosities and the injected lengths were almost perfectly correlated. Furthermore, two dry powder rheology metrics, namely, the normalized basic flow energy and the conditioned powder bulk density, showed the correlation with the feedstock moldability which is comparable to that obtained with the melt rheology. The results of this study indicate that although the feedstock melt viscosity and the dry powder rheology take fewer variables into account as compared to real-scale injections, these simplified tests (especially dry powder rheology) could be considered as rapid and reliable approaches to assessing the impact of powder characteristics on the moldability of powder-binder feedstocks used in metal injection molding.

Influence of powder characteristics on the structural and the mechanical properties of additively manufactured Zr-based bulk metallic glass

Additive manufacturing of Zr-based bulk metallic glasses (BMGs) is subject to growing scientific and industrial attention. Laser-based powder bed fusion of metals (PBF-LB/M) becomes a key technology to overcome current restrictions of size and geometry in the manufacturing of BMGs. For industrial application, further knowledge about defect formation, such as porosity and crystallization, is mandatory to develop processing strategies and suitable quality assurance. In this context, the influence of the particle size distribution, oxygen contamination, and applied process parameters during the PBF-LB/M of the glass-forming alloy AMZ4 (in at.% Zr59.3Cu28.8Al10.4Nb1.5) on the structural and mechanical properties were evaluated. It was found that the addition of SiO2 flow aid to the feedstock is suitable to increase flowability without impeding fabrication of the amorphous material. Furthermore, the processing of partially crystalline powder particles into amorphous samples is demonstrated. It indicates that today’s high effort producing amorphous powders and thus the production costs can be reduced. Flexural bending tests and high-energy synchrotron X-ray diffraction reveal that the powder feedstock’s oxygen content is crucial for the amorphization, embrittlement, and flexural strength of PBF-LB/M processed Zr-based BMGs.

Modeling and simulation of powder spreading of Inconel 625 based on 3DP process

Three-Dimensional Printing (3DP) forming technology has the advantages of rapid forming speed, wide range of printing materials, unlimited printing shape and no need for supporting materials. In this paper, the Discrete Element Method (DEM) is used to simulate the powder spreading process of Inconel 625. The influence of powder particle shape, powder ratio, roller size and roller horizontal speed on powder spreading is simulated. The results show that the horizontal velocity of powder laying roller and the shape of powder particles have great influence on the accuracy of powder spreading. The influence of powder characteristics on the forming quality is studied. It is found that if the particle size of powder is smaller, the fluidity will be lower, and the forming quality will be better; if the particle size of powder is larger, the fluidity will be better, but the precision of the part will be reduced. The results provide a theoretical basis for the preparation of Inconel 625 by using 3DP process.

Influence of powder characteristics on cold sintering of nano-sized ZnO with density above 99 %

Cold sintering parameters such as, temperature, pressure, aqueous phase, heating rate and dwelling time has been widely discussed in the literature but the role of starting powder with respective microstructure development is mostly overlooked. There is a need for understanding the effect of powder agglomerates and the role of inter particle friction on the densification behavior during cold sintering process. Present study encompasses investigation and optimization of these parameters for ZnO which enabled > 99 % of relative density with grain sizes below 200 nm. Additionally, role of external atmosphere was also studied to investigate its impact on densification during the process. All cold sintering experiments were carried out in a FAST/SPS device for studying aqueous phase evaporation and ensuring the reproducibility of process parameters. Microstructure characterization (scanning and transmission electron microscopy) showed – without any post heat treatment– defect free grain boundary structure opposite to what documented by previous studies.

A detailed microstructural and corrosion analysis of magnesium alloy WE43 manufactured by selective laser melting

The production of magnesium alloy WE43 was achieved by selective laser melting (SLM). The alloy was investigated after SLM, hot isostatic pressing (HIP), and solutionising heat treatment. The microstructure and corrosion behaviour of the specimens were carefully characterised, whilst assessed and contrast relative to the conventionally cast alloy counterpart. The SLM prepared specimens possess a unique microstructure comprising fine grains growing with a strong [0001] texture along the building direction with a low fraction of process-induced and metallurgical defects, reaching < 0.1 %, after optimising the SLM parameters and the HIP treatment. Electrochemical measurements demonstrated that the SLM prepared WE43 is cathodically more active as compared with its cast counterpart. It is proposed that this behaviour is due to a high density of zirconium-rich oxide particles uniformly distributed throughout the alloy microstructure as well as the alterations in the chemical composition of the solid-solution matrix originating from the high cooling rates of SLM. It was also noted that the oxide particles are mainly sourced by powder. The present results suggest that the corrosion of SLM prepared Mg alloys could be greatly improved once the influence of powder characteristics is further understood and controlled.

Influence of powder characteristics on shrinkage behavior of 3D-Printed glass structures

The anisotropy of shrinkage that occurs during the sintering of glass needs to be carefully understood for proper fabrication of 3-dimensional (3D) glass structures using a binder-jetting additive manufacturing process. Although the time-dependence of glass sintering is governed by viscous flow, the effect of the powder characteristics and process parameters during printing need to be considered. In this study, the size and morphology of glass powders were varied as material parameters for obtaining optimal powder characteristics. Glasses composed of SiO2–B2O3–ZnO–BaO–Al2O3, with different sizes and morphologies, were used as printing materials. Different powder stacking orientations were considered as additional parameters affecting shrinkage behavior. The anisotropy degree was obtained by measuring the ratio between the axial contraction and the radial contraction of samples sintered for different amounts of time. Both frit and glass bead exhibited anisotropic shrink behavior. However, the spherical glass bead was the closest to isotropic shrinkage and showed an effective shrinkage rate for the formation of a designed 3D glass structure and densification of the microstructure.

Correlation of Feedstock Powder Characteristics with Microstructure, Composition, and Mechanical Properties of La2Ce2O7 Coatings Produced by Plasma Spray-Physical Vapor Deposition

By virtue of plasma spray-physical vapor deposition (PS-PVD) process, coatings in possession of columnar structures can be obtained by suitable processing parameters coupled with specially designed powder feedstock. In this paper, the influence of powder characteristics on the La2Ce2O7 (LC) coating microstructures was investigated by using three kinds of feedstock powders with same PS-PVD processing parameters. It was found that small agglomerated feedstock, weak binding strength, and small primary particle sizes can enhance the feedstock evaporation rate, thus obtaining well columnar structured coatings. X-ray diffraction (XRD) patterns revealed that except for a very small amount of La2O3 the main phase of all the coatings is LC. The La/Ce atomic ratios reduced in the coatings compared to the feedstocks, especially the coatings with better columnar structure. Super-lattice patterns were observed by transmission electron microscope (TEM), which means that the LC phase is supposed to be pyrochlore structure. Furthermore, the mechanical properties evaluated by nano-indentation tests indicated that both the hardness and Young’s modulus of each coating show negative correlations with the porosity inside the columns.

Effect of powder characteristics on production of oxide dispersion strengthened Fe[sbnd]14Cr steel by laser powder bed fusion

In order to assess the potentialities of additive manufacturing in nuclear industry, Oxide Dispersion Strengthened (ODS) Fe14Cr steels are produced by laser powder bed fusion (L-PBF). Such materials are currently manufactured by milling a Fe14Cr atomized powder with Y2O3 and TiH2 powders. The resulting powder has a non-spherical shape being coarser than powders typically used in L-PBF equipment. The influence of powder characteristics on the processability of ODS Fe14Cr by L-PBF are studied in details. Four different powders are used. These powders differ from size, morphology and chemical composition. Finer is the powder; wider is the process range to obtain dense samples. This phenomenon could be mitigated by transferring an amount of energy superior to 110 J.mm−3. The presence of yttrium and titanium gives columnar microstructure for ODS samples, whereas Fe14Cr samples have stirred microstructure. Titanium and yttrium form oxides, which enlarge the melt pool and induce columnar growth.

Influence of powder characteristics on the microstructure and mechanical properties of HIPped CM247LC Ni superalloy

This work investigates the influence of gas atomised powder particle size and characteristics on the microstructure and mechanical properties of hot isostatically pressed (HIPped) CM247LC nickel-base superalloy powders. Three different GA powders (particle size ranges: 53–150 μm; 0–150 μm; 15–53 μm) of very similar compositions were HIPped at the γ' solvus temperature. Microstructural analysis and tensile testing were conducted on as-HIPped samples. It was found that the fine powders promote the formation of prior particle boundaries (PPBs) decorated with carbide and oxy-carbide clusters due to the higher oxygen content per weight in fine powders, which adversely affects the mechanical properties. It was also found that coarse powder particles are beneficial for minimising PPBs and increasing the twin boundaries fraction. Nonetheless, the best balance of high temperature tensile properties was in the wide range powder (0–150 μm). The effect of particle size was further investigated by sieving the wide range powder into two particle size distributions. Tensile testing of these conditions showed that the hot ductility could be further improved by removing the very fine powder particles. Both of the sieved powders exhibited better hot ductility than the wide range powder and also outperformed the 53–150 μm and 15–53 μm powders.

Influence of powder characteristics and additive manufacturing process parameters on the microstructure and mechanical behaviour of Inconel 625 fabricated by Selective Laser Melting

Selective Laser Melting (SLM) as an additive manufacturing process can fabricate near to net shape metallic components directly from Computer aided design models, which may be difficult to fabricate using conventional manufacturing methods. In this work, the powdered metals used as the raw material feedstock in the Selective Laser Melting (SLM) process were studied. SLM manufacturing processibility of nickel based super alloy, powders related to the particle Size Distribution (PSD), flow ability, mechanical properties and microstructures was investigated. Different powder characterisation methods were also investigated to establish which might be most useful for SLM application. Three different Inconel 625 (IN625) powder feedstock materials have been accounted for this study. Firstly, three different IN625 powders were fully characterised for chemical composition, particle size distribution and flow ability using different types of characterisation techniques. It has been found that the presence of any significant proportion of powder particles smaller than 10-μm diameter, leads to severe agglomeration and make SLM processing difficult. Secondly, coupons were manufactured using SLM from each powder with different process parameter, which were analysed for porosity and mechanical behaviour. Next, the scanning electron microscopy (SEM), electron back scattering diffraction (EBSD) are employed to investigate the microstructures. Finally, data analysis was employed on the data collected by metal powders characterization, SLM manufacturing, SEM/EBSD study and mechanical properties of the IN625. It has been observed that the powder characteristics, as well as SLM process parameters influences on the quality of the IN625 fabricated.

Microstructure and Erosion Properties of HVOF Sprayed Cermet Coatings via Different Feedstock Powders

In the present study, Cr3C2-NiCr and WC-Co coatings have been deposited using high velocity oxygen-fuel (HVOF) spray technology from five available powders with various bonding phase content or manufacturing process. The microstructure of coatings was observed by scanning electron microscopy (SEM). Microhardness and erosion performance of the coatings were studied. The influence of powder characteristics on the microstructure and erosion performance of coatings was also investigated. The results indicated that an independent bonding phase distributed in the feedstock powder can effectively improve the erosion resistance of Cr3C2-NiCr coatings although the microhardness of the coatings may be lower. Deformation of the free NiCr binder layer in the coating is probably to prevent nucleation and propagation of cracks, which may result in improving the erosion resistance of the coating. Nano WC-Co coatings reached lower erosion resistance than micro WC-Co coatings due to the higher porosity and lower microhardness of nano WC-Co coatings.

Influence of Powder Characteristics on Processability of AlSi12 Alloy Fabricated by Selective Laser Melting.

Selective laser melting (SLM) is one of the additive manufacturing technologies that allows for the production of parts with complex shapes from either powder feedstock or from wires. Aluminum alloys have a great potential for use in SLM especially in automotive and aerospace fields. This paper studies the influence of starting powder characteristics on the processability of SLM fabricated AlSi12 alloy. Three different batches of gas atomized powders from different manufacturers were processed by SLM. The powders differ in particle size and its distribution, morphology and chemical composition. Cubic specimens (10 mm × 10 mm × 10 mm) were fabricated by SLM from the three different powder batches using optimized process parameters. The fabrication conditions were kept similar for the three powder batches. The influence of powder characteristics on porosity and microstructure of the obtained specimens were studied in detail. The SLM samples produced from the three different powder batches do not show any significant variations in their structural aspects. However, the microstructural aspects differ and the amount of porosity in these three specimens vary significantly. It shows that both the flowability of the powder and the apparent density have an influential role on the processability of AlSi12 SLM samples.

Influence of Powder Characteristics on Formation of Porosity in Additive Manufacturing of Ti-6Al-4V Components

This paper aims to study the genesis of defects in titanium components made through two different additive manufacturing technologies: selective laser melting and electron beam melting. In particular, we focussed on the influence of the powders used on the formation of porosities and cavities in the manufactured components. A detailed experimental campaign was carried out to characterize the components made through the two additive manufacturing techniques aforementioned and the powders used in the process. It was found that some defects of the final components can be attributed to internal porosities of the powders used in the manufacturing process. These internal porosities are a consequence of the gas atomization process used for the production of the powders themselves. Therefore, the importance of using tailored powders, free from porosities, in order to manufacture components with high mechanical properties is highlighted.

Influence of powder characteristics on hot-pressed Si3N4 ceramics

In this paper, the influence of the starting powder characteristics for five commercial Si3N4 powders on sintering behavior, microstructure and mechanical properties of hot-pressed Si3N4 ceramics with and without the addition of La2O3-Yb2O3-MgO sintering additives was investigated. For the system without sintering additives, the high amount of the impurities in the starting powders could facilitate the densification process and promote ?-Si3N4 grain growth. However, large whisker-like particles (? phase) present in the initial powders inhibited the sintering process, which led to a lower density of Si3N4 ceramics. On the other hand, when the sintering additives were introduced in the beginning stage of the powder processing step, the effects of impurities content and particle morphology in the initial powders on the densification and microstructure were not apparent. There was tendency that finer powder size resulted in finer microstructure. However, a high ?-phase ratio in the initial powders could accelerate the abnormal grain growth and thus lead to better mechanical properties.

State of the art in powder-mixed electric discharge machining: A review

Accomplishment of high machining rates along with good surface quality is a major concern in electric discharge machining process. Powder-mixed electric discharge machining in which suitable powder particles are impregnated in dielectric has gone forth as a potential solution to this problem. Nevertheless, challenges such as dielectric circulation, homogeneous blending of the powder particles in the dielectric, debris removal and quantity of the powder material required have to be addressed carefully before implementing this process on a large scale in the manufacturing industry. Extensive research in the field of electric discharge machining using powder-suspended dielectrics has started only in the recent years. In this article, a comprehensive review of the research going on in the field of powder-mixed electric discharge machining is presented. The emphasis is given on powder-mixed electric discharge machining mechanism, influence of powder characteristics and machining parameters on various responses. Some of the major application areas, variants of the basic powder-mixed electric discharge machining process and possibilities of further improvement are also discussed.