Influence of the particle size distribution of monomodal 316L powder on its flowability and processability in powder bed fusion

Powder bed fusion (PBF) is the most commonly adopted additive manufacturing process for fabricating complex metal parts via the layer-wise melting of a powder bed using a laser beam. However, the qualification of PBF-manufactured parts remains challenging and expensive, thereby limiting the broader industrialization of the technology. Powder characteristics significantly influence part properties, and understanding the influencing factors contributes to effective quality standards for PBF. In this study, the influence of the particle size distribution (PSD) median and width on powder flowability and part properties is investigated. Seven gas-atomized SS316L powders with monomodal PSDs, a median particle size ranging from 10 μm to 60 μm, and a distribution width of 15 μm and 30 μm were analyzed and subsequently processed. The PBF-manufactured parts were analyzed in terms of density and melt pool dimensions. Although powder flowability was inversely related to the median particle size, it was unrelated to the distribution width. An inverse relationship between the median particle size and the part density was observed; however, no link was found to the distribution width. Likely, the melt pool depth and width fluctuation significantly influence the part density. The melt pool depth decreases and the width fluctuation increases with an increasing median particle size.

Production and investigation of powders for additive synthesis from a new beta-solidifying TiAl-based alloy

Chemical composition, structure, and technological properties have been investigated for metal powder compositions (MPCs) of a new six-component TiAl-based alloy with Gd microadditions: Ti-31.0Al-2.5V-2.5Nb-2.5Cr-0.4Gd, wt.% (Ti-44.5Al-2V-1Nb-2Cr-0.1Gd, at.%). Three MPCs fractions (10–63, 40–100, 80–120 μm) were produced by electrode induction melting and inert gas atomization technique and targeted for the additive synthesis of parts. It is shown that the chemical composition of the MPCs for the main elements corresponds to that of the electrode. In contrast, a 1.5-fold increase of the oxygen content in the MPCs was observed, which is being the result of natural oxidation of powder particles upon air environment due to developed specific surface. It has been determined that the phase composition of the MPCs (γ+α(α2)+β) differs from the equilibrium phase composition of the electrode (γ+α2)+β0/B2) and corresponds to a rapidly quenched metastable state, which indicates high solidification rates in the atomization process, exceeding critical cooling rates of the alloy. The technological properties, specifically the powder flowability, were found to be improved for 40–100 and 80–120 μm fractions, making them applicable for additive synthesis of parts from the studied alloy by selective electron-beam melting method

Potential of Chickpea Flours with Different Microstructures as Multifunctional Ingredient in an Instant Soup Application

Chickpea flours are an interesting multifunctional ingredient for different food products. This study investigated the potential of differently processed chickpea flours as alternative thickening agents in an instant soup recipe, replacing potato starch. Dry instant soup powders were compared on bulk density and powder flowability, whereas prepared liquid instant soups were studied in terms of rheological behaviour (as influenced by microstructure) and volatile composition. The chickpea-flour-containing soup powders possessed similar powder flowability to a reference powder but were easier to mix and will potentially result in reduced blockages during filling. For prepared liquid instant soups, similar viscosities were reached compared to the potato starch reference soup. Nevertheless, the chickpea-flour-containing soups showed higher shear thinning behaviour due to the presence of larger particles and the shear induced breakdown of particle clusters. Flavour compounds from the soup mix interacted with chickpea flour constituents, changing their headspace concentrations. Additionally, chickpea flours introduced new volatile compounds to the soups, such as ketones, aldehydes, alcohols, and sulphur compounds, which can possibly alter the aroma and flavour. It was concluded that chickpea flours showed excellent potential as alternative thickening ingredient in instant soups, improving the protein, mineral and vitamin content, and the powder flowability of the soups, although the flavour of the soups might be affected by the changes in volatile profiles between the soups.

Effect of Particle Size and Shape on Flowability of FGH96 Superalloy Powder

The effect of particle size and shape on flowability of FGH96 superalloy powder was investigated by field emission scanning electron microscopy (FE-SEM), laser particle size analyzer (LPSA) and X-ray photoelectron spectroscopy (XPS). The results showed that the powder flowability basically presented a decreasing trend as the median diameter decreased. The Hall velocity of the five median diameter powders (50=203.9 μm, 106.3 μm, 83.2 μm, 73.8 μm, 19.9 μm) was 27.18 s/50g, 23.25 s/50g, 23.86 s/50g, 23.42 s/50g and none, respectively. The surface oxides/ hydroxide/nitride of the five median diameter powders were mostly the same, mainly including Al2O3, Cr2O3, MoO3, Nb2O5, Ni (OH)2, TiO2 and TiN. The median diameter 50, shape factors (circularity, aspect ratio, roundness, solidity) and fractal dimension were selected to quantitatively characterize particle size and shape. For the same fluctuation value of powder flowability, the roundness and solidity showed lower sensitivity. Compared with the two shape factors, the sensitivity of circularity and aspect ratio was at an intermediate level, while the median diameter and fractal dimension displayed higher sensitivity. The median diameter and fractal dimension can be used to characterize the principal variation of flowability. The circularity and aspect ratio can be utilized to characterize the variation of flowability supplementally.