Revealing Particle-Scale Powder Spreading Dynamics in Powder-Bed-Based Additive Manufacturing Process by High-Speed X-Ray Imaging

Powder spreading is a key step in the powder-bed-based additive manufacturing process, which determines the quality of the powder bed and, consequently, affects the quality of the manufactured part. However, powder spreading behavior under additive manufacturing condition is still not clear, largely because of the lack of particle-scale experimental study. Here, we studied particle-scale powder dynamics during the powder spreading process by using in-situ high-speed high-energy x-ray imaging. Evolution of the repose angle, slope surface speed, slope surface roughness, and the dynamics of powder clusters at the powder front were revealed and quantified. Interactions of the individual metal powders, with boundaries (substrate and container wall), were characterized, and coefficients of friction between the powders and boundaries were calculated. The effects of particle size on powder flow dynamics were revealed. The particle-scale powder spreading dynamics, reported here, are important for a thorough understanding of powder spreading behavior in the powder-bed-based additive manufacturing process, and are critical to the development and validation of models that can more accurately predict powder spreading behavior

Experimental investigation of critical suction velocity of coarse solid particles in hydraulic collecting

Hydraulic collecting and pipe transportation are regarded as an efficient way for exploiting submarine mineral resources such as the manganese nodules and ores. Coarse particles on the surface of the sea bed are sucked by a pipe during the mining and crushing of the mineral. In this paper, the critical suction velocity for lifting the coarse particles is investigated through a series of laboratory experiments, and the solid-liquid two-phase flow characteristics are obtained. Based on the dimensional analysis, the geometric similarity is found between actual exploitation process and model test with the same kind of material. The controlling dimensionless parameters such as the hydraulic collecting number, the relative coarse particle diameter, the relative suction height, and the density ratio are deduced and discussed. The results show that the logarithm in base 10 of the hydraulic collecting number increases approximately linearly with the increase of the relative suction height, while decreases with the relative particle diameter. A fitting formula for predicting the critical suction velocity is presented according to the experimental results

Experimental investigation of critical suction velocity of coarse solid particles in hydraulic collecting

Hydraulic collecting and pipe transportation are regarded as an efficient way for exploiting submarine mineral resources such as the manganese nodules and ores. Coarse particles on the surface of the sea bed are sucked by a pipe during the mining and crushing of the mineral. In this paper, the critical suction velocity for lifting the coarse particles is investigated through a series of laboratory experiments, and the solid-liquid two-phase flow characteristics are obtained. Based on the dimensional analysis, the geometric similarity is found between actual exploitation process and model test with the same kind of material. The controlling dimensionless parameters such as the hydraulic collecting number, the relative coarse particle diameter, the relative suction height, and the density ratio are deduced and discussed. The results show that the logarithm in base 10 of the hydraulic collecting number increases approximately linearly with the increase of the relative suction height, while decreases with the relative particle diameter. A fitting formula for predicting the critical suction velocity is presented according to the experimental results

Defect and satellite characteristics of additive manufacturing metal powders

Metal additive manufacturing (AM) requires high-quality metal powders to three-dimensionally (3D) print metallic components with complex and customizable geometries. The lack of quantification of AM metal powders creates quality control challenges for 3D printed components, increases the uncertainty of printing reliability and net cost of inspected and certified printed components, and reduces the recyclability of used powders. However, critical characteristics of AM metal powders that are decisive factors for the 3D printing process, such as internal porosity, contamination, and satellite feature, remain ambiguous. In this work, we developed a novel approach to 3D quantify key characteristics of AM metal powders down to individual particles by using high-resolution synchrotron x-ray computed tomography. Empowered by the penetrative capability of high-energy x-ray, internal porosity and contamination within as-atomized metal powders from high-entropy alloys to nickel-based superalloys were evaluated. Additionally, the newly-developed dispersion method enables the homogeneous separation of individual particles, and consequently, results in the implementation of 3D particle shape analysis. To resolve a major challenge of identification and quantification of satellite-feature particles in as-atomized AM metal powders, the satellite features were quantitated by modeling and analyzing the shape parameter of local thickness variance. Furthermore, the 3D analytical methods of particle assessment in this study can be applied to other materials systems like rock, food, and pharmaceutical particles, and provide insights for process optimization across powder metallurgy, concrete, food and pharmaceutical manufacturing, and AM industries.This is a manuscript of an article published as Xiong, Lianghua, Andrew Chihpin Chuang, Jonova Thomas, Timothy Prost, Emma White, Iver Anderson, and Dileep Singh. "Defect and satellite characteristics of additive manufacturing metal powders." Advanced Powder Technology 33, no. 3 (2022): 103486. DOI: 10.1016/j.apt.2022.103486. Copyright 2022 The Society of Powder Technology Japan. Posted with permission. DOE Contract Number(s): AC02-06CH11357; AC02-07CH11358

Investigating Powder Spreading Dynamics in Additive Manufacturing Processes by In-Situ High-Speed X-Ray Imaging

The quality of the powder bed is known to be one of the main factors that influence the quality of the part being manufactured by powder-bed-based additive manufacturing processes

Revealing particle-scale powder spreading dynamics in powder-bed-based additive manufacturing process by high-speed x-ray imaging

Abstract Powder spreading is a key step in the powder-bed-based additive manufacturing process, which determines the quality of the powder bed and, consequently, affects the quality of the manufactured part. However, powder spreading behavior under additive manufacturing condition is still not clear, largely because of the lack of particle-scale experimental study. Here, we studied particle-scale powder dynamics during the powder spreading process by using in-situ high-speed high-energy x-ray imaging. Evolution of the repose angle, slope surface speed, slope surface roughness, and the dynamics of powder clusters at the powder front were revealed and quantified. Interactions of the individual metal powders, with boundaries (substrate and container wall), were characterized, and coefficients of friction between the powders and boundaries were calculated. The effects of particle size on powder flow dynamics were revealed. The particle-scale powder spreading dynamics, reported here, are important for a thorough understanding of powder spreading behavior in the powder-bed-based additive manufacturing process, and are critical to the development and validation of models that can more accurately predict powder spreading behavior

The effects of fertility and synchronization variation on seed production in two Chinese fir clonal seed orchards

Abstract Variations in fertility and synchronization information is fundamental to seed orchard management. Our objective was to determine clonal variation and stability in strobili production, phenology, synchronization, and seed production in two generation clonal seed orchards (CSO) of Chinese fir. The number of female and male strobili and the phenology of 42 clones in both the 2.0- and 2.5-generation clonal seed orchards were investigated and recorded to calculate the variation and stability of fertility and synchronization. In both seed orchards, an obvious variation in gamete contribution was found among clones, indicating deviation from random mating. Female receptivity was in the pollen shedding stage, which is favorable to pollination. However, low synchronization (mean POij = 0.283) between clones indicated low overlap between female receptivity and pollen shedding. A higher POij value within clones than within outcrossing combinations indicated a high risk of selfing in two seed orchards, particularly for early- and late-flowering clones. The number of female strobili and POij (as female) significantly influence seed production. Overall, fertility and synchronization variation had notable consequences for seed production. Scientific genetic management is indispensable for promoting fertility uniformity and synchronization to obtain maximal genetic gain

Transient Dynamics of Powder Spattering in Laser Powder Bed Fusion Additive Manufacturing Process Revealed by In-Situ High-Speed High-Energy X-Ray Imaging

Powder spattering is a major cause of defect formation and quality uncertainty in the laser powder bed fusion (LPBF) additive manufacturing (AM) process. It is very difficult to investigate this with either conventional characterization tools or modeling and simulation. The detailed dynamics of powder spattering in the LPBF process is still not fully understood. Here, we report insights into the transient dynamics of powder spattering in the LPBF process that was observed with in-situ high-speed high-energy x-ray imaging. Powder motion dynamics, as a function of time, environment pressure, and location, is presented. The moving speed, acceleration, and driving force of powder motion that are induced by metal vapor jet/plume and argon gas flow are quantified. A schematic map showing the dynamics and mechanisms of powder motion during the LPBF process as functions of time and pressure is constructed. Potential ways to mitigate powder spattering during the LPBF process are discussed and proposed, based on the revealed powder motion dynamics and mechanisms