Spreadability Testing of Powder for Additive Manufacturing

AbstractThe spreading of powders into thin layers is a critical step in powder bed additive manufacturing, but there is no accepted technique to test it. There is not even a metric that can be used to describe spreading behaviour. A robust, image-based measurement procedure has been developed and can be implemented at modest cost and with minimal training. The analysis is automated to derive quantitative information about the characteristics of the spread layer. The technique has been demonstrated for three powders to quantify their spreading behaviour as a function of layer thickness and spreading speed.

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Experimental Studies on Laser Additive Manufacturing of Inconel-625 Structures Using Powder Bed Fusion at 100 µm Layer Thickness

Journal of Materials Engineering and Performance ◽

10.1007/s11665-020-05215-9 ◽

2020 ◽

Vol 29 (11) ◽

pp. 7636-7647

Author(s):

S. K. Nayak ◽

S. K. Mishra ◽

A. N. Jinoop ◽

C. P. Paul ◽

K. S. Bindra

Keyword(s):

Additive Manufacturing ◽

Layer Thickness ◽

Experimental Studies ◽

Inconel 625 ◽

Powder Bed Fusion ◽

Laser Additive Manufacturing ◽

Powder Bed

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Analysis of Density, Roughness, and Accuracy of the Atomic Diffusion Additive Manufacturing (ADAM) Process for Metal Parts

Materials ◽

10.3390/ma12244122 ◽

2019 ◽

Vol 12 (24) ◽

pp. 4122 ◽

Cited By ~ 1

Author(s):

Manuela Galati ◽

Paolo Minetola

Keyword(s):

Additive Manufacturing ◽

Layer Thickness ◽

Dimensional Accuracy ◽

Raw Material ◽

Atomic Diffusion ◽

Powder Bed ◽

Metal Parts ◽

Unique System ◽

Am Processes ◽

Metal Additive

Atomic Diffusion Additive Manufacturing (ADAM) is a recent layer-wise process patented by Markforged for metals based on material extrusion. ADAM can be classified as an indirect additive manufacturing process in which a filament of metal powder encased in a plastic binder is used. After the fabrication of a green part, the plastic binder is removed by the post-treatments of washing and sintering (frittage). The aim of this work is to provide a preliminary characterisation of the ADAM process using Markforged Metal X, the unique system currently available on the market. Particularly, the density of printed 17-4 PH material is investigated, varying the layer thickness and the sample size. The dimensional accuracy of the ADAM process is evaluated using the ISO IT grades of a reference artefact. Due to the deposition strategy, the final density of the material results in being strongly dependent on the layer thickness and the size of the sample. The density of the material is low if compared to the material processed by powder bed AM processes. The superficial roughness is strongly dependent upon the layer thickness, but higher than that of other metal additive manufacturing processes because of the use of raw material in the filament form. The accuracy of the process achieves the IT13 grade that is comparable to that of traditional processes for the production of semi-finished metal parts.

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On the measurement of effective powder layer thickness in laser powder-bed fusion additive manufacturing of metals

Progress in Additive Manufacturing ◽

10.1007/s40964-018-0064-0 ◽

2018 ◽

Vol 4 (2) ◽

pp. 109-116 ◽

Cited By ~ 9

Author(s):

Yahya Mahmoodkhani ◽

Usman Ali ◽

Shahriar Imani Shahabad ◽

Adhitan Rani Kasinathan ◽

Reza Esmaeilizadeh ◽

...

Keyword(s):

Additive Manufacturing ◽

Layer Thickness ◽

Powder Layer ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Powder Bed

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Discrete Element Simulation of the Effect of Roller-Spreading Parameters on Powder-Bed Density in Additive Manufacturing

Materials ◽

10.3390/ma13102285 ◽

2020 ◽

Vol 13 (10) ◽

pp. 2285

Author(s):

Jiangtao Zhang ◽

Yuanqiang Tan ◽

Tao Bao ◽

Yangli Xu ◽

Xiangwu Xiao ◽

...

Keyword(s):

Additive Manufacturing ◽

Layer Thickness ◽

Rotational Speed ◽

High Performance ◽

Ceramic Powder ◽

Discrete Element ◽

Parameters Optimization ◽

Powder Layer ◽

Translational Velocity ◽

Powder Bed

The powder-bed with uniform and high density that determined by the spreading process parameters is the key factor for fabricating high performance parts in Additive Manufacturing (AM) process. In this work, Discrete Element Method (DEM) was deployed in order to simulate Al2O3 ceramic powder roller-spreading. The effects of roller-spreading parameters include translational velocity Vs, roller’s rotational speed ω, roller’s diameter D, and powder layer thickness H on powder-bed density were analyzed. The results show that the increased translational velocity of roller leads to poor powder-bed density. However, the larger roller’s diameter will improve powder-bed density. Moreover, the roller’s rotational speed has little effect on powder-bed density. Layer thickness is the most significant influencing factor on powder-bed density. When layer thickness is 50 μm, most of particles are pushed out of the build platform forming a lot of voids. However, when the layer thickness is greater than 150 μm, the powder-bed becomes more uniform and denser. This work can provide a reliable basis for roller-spreading parameters optimization.

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A Comprehensive Approach to Powder Feedstock Characterization for Powder Bed Fusion Additive Manufacturing: A Case Study on AlSi7Mg

Materials ◽

10.3390/ma11122386 ◽

2018 ◽

Vol 11 (12) ◽

pp. 2386 ◽

Cited By ~ 18

Author(s):

Jose Muñiz-Lerma ◽

Amy Nommeots-Nomm ◽

Kristian Waters ◽

Mathieu Brochu

Keyword(s):

Additive Manufacturing ◽

Surface Energy ◽

Particle Distribution ◽

Particle Surface ◽

Moisture Sorption ◽

Thin Layers ◽

Spherical Particles ◽

Powder Bed Fusion ◽

Powder Bed ◽

Powder Feedstock

In powder bed fusion additive manufacturing, the powder feedstock quality is of paramount importance; as the process relies on thin layers of powder being spread and selectively melted to manufacture 3D metallic components. Conventional powder quality assessments for additive manufacturing are limited to particle morphology, particle size distribution, apparent density and flowability. However, recent studies are highlighting that these techniques may not be the most appropriate. The problem is exacerbated when studying aluminium powders as their complex cohesive behaviors dictate their flowability. The current study compares the properties of three different AlSi7Mg powders, and aims to obtain insights about the minimum required properties for acceptable powder feedstock. In addition to conventional powder characterization assessments, the powder spread density, moisture sorption, surface energy, work of cohesion, and powder rheology, were studied. This work has shown that the presence of fine particles intensifies the pick-up of moisture increasing the total particle surface energy as well as the inter-particle cohesion. This effect hinders powder flow and hence, the spreading of uniform layers needed for optimum printing. When spherical particles larger than 48 µm with a narrow particle distribution are present, the moisture sorption as well as the surface energy and cohesion characteristics are decreased enhancing powder spreadability. This result suggest that by manipulating particle distribution, size and morphology, challenging powder feedstock such as Al, can be optimized for powder bed fusion additive manufacturing.

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Effect of Laser Energy Density on Bulk Properties of SS 316L Structures Built by Laser Additive Manufacturing Using Powder Bed Fusion

Volume 2: Combustion, Fuels, and Emissions; Renewable Energy: Solar and Wind; Inlets and Exhausts; Emerging Technologies: Hybrid Electric Propulsion and Alternate Power Generation; GT Operation and Maintenance; Materials and Manufacturing (Including Coatings, Composites, CMCs, Additive Manufacturing); Analytics and Digital Solutions for Gas Turbines/Rotating Machinery ◽

10.1115/gtindia2019-2452 ◽

2019 ◽

Author(s):

Saurav K. Nayak ◽

Sanjay K. Mishra ◽

Christ P. Paul ◽

Arackal N. Jinoop ◽

Sunil Yadav ◽

...

Keyword(s):

Additive Manufacturing ◽

Energy Density ◽

Layer Thickness ◽

Laser Energy ◽

Advanced Technology ◽

Incomplete Fusion ◽

Laser Energy Density ◽

Powder Bed Fusion ◽

Laser Additive Manufacturing ◽

Powder Bed

Abstract Laser Additive Manufacturing using Powder Bed Fusion (LAM-PBF) is one of the revolutionary technologies playing a key role in fourth industrial revolution for redefining manufacturing from mass production to mass customization. To upkeep the pace, Raja Ramanna Centre for Advanced Technology (RRCAT) has indigenously developed an LAM-PBF system and it is being used for process and component development for various engineering applications. This paper reports a parametric investigation to evaluate the influence of process parameters on the sample properties and to develop the process window for fabricating complex shaped engineering components. In the present work, an experimental investigation is carried out to investigate the effect of Laser Energy density (LED) on the porosity, microstructure and mechanical properties of SS 316L bulk structures fabricated by LAM-PBF system. LED is a combined parameter simultaneously considering the effect of Laser Power (P), Scan Speed (v), hatch spacing (h) and layer thickness (t). The effect of three LED values such as 83.33 J/mm3, 253.97 J/mm3 and 476.19 J/mm3 is investigated in the present work by building cuboidal samples at a layer thickness of 75 microns. Porosity is estimated using area fraction method in optical microscopy and it is found that the minimum porosity of 0.14 % and pore area of 1.28 mm2 are observed at 253.97 J/mm3. Maximum porosity of 18.85 % is observed at 83 J/mm3 due to incomplete fusion defects. However, porosity observed at 475 J/mm3 is 6.56 % with average pore size of 17.8 mm2. Microstructural studies show primarily columnar growth in all the samples with fine dendrites. The dendrite size is observed to be 3.2 μm, 2.4 μm and 1.46 μm at 83.33 J/mm3, 253.97 J/mm3 and 476.19 J/mm3 respectively. Micro-hardness and single cycle automatic ball indentation studies are found to be in agreement with dendritic size, with lower hardness at larger dendrite size. X-Ray Diffraction (XRD) studies indicate similar peaks at all the conditions, with slight peak shift observed with increase in LED primarily due to higher amount of residual stress. Thus, it can be inferred that LED of 253.97 J/mm3 is suitable for fabricating engineering components due to combination of lower porosity and fine dendritic structure.

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Simulation Study of Hatch Spacing and Layer Thickness Effects on Microstructure in Laser Powder Bed Fusion Additive Manufacturing using a Texture-Aware Solidification Potts Model

Journal of Materials Engineering and Performance ◽

10.1007/s11665-021-06110-7 ◽

2021 ◽

Author(s):

Joseph Pauza ◽

Anthony Rollett

Keyword(s):

Additive Manufacturing ◽

Layer Thickness ◽

Potts Model ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Microstructure Control ◽

Powder Bed ◽

Laser Parameters ◽

Link Type ◽

Hatch Spacing

AbstractMicrostructure control in the laser powder bed fusion additive manufacturing processes is a topic of major interest because of the submillimeter length scale at which the manufacturing process occurs. The ability to control the process at the melt pool scale allows for microstructure control that few other manufacturing techniques can match. The majority of work on microstructure control has focused on altering laser parameters to control solidification conditions (Ref (R.R. Dehoff, M.M. Kirka, W.J. Sames, H. Bilheux, A.S. Tremsin, L.E. Lowe, and S.S. Babu, Site Specific Control of Crystallographic Grain Orientation through Electron Beam Additive Manufacturing, Mater. Sci. Technol., 2014, 31(8), p 931–938. R. Shi, S.A. Khairallah, T.T. Roehling, T.W. Heo, J.T. McKeown, and M.J. Matthews, Microstructural Control in Metal Laser Powder Bed Fusion Additive Manufacturing Using Laser Beam Shaping Strategy, Acta Mater., 2020, 184, p 284–305, https://doi.org/10.1016/j.actamat.2019.11.053.)). Other machine parameters, besides the laser parameters, have also been shown to affect the microstructure of AM parts (Ref (N. Nadammal, S. Cabeza, T. Mishurova, T. Thiede, A. Kromm, C. Seyfert, L. Farahbod, C. Haberland, J.A. Schneider, P.D. Portella, and G. Bruno, Effect of Hatch Length on the Development of Microstructure, Texture and Residual Stresses in Selective Laser Melted Superalloy Inconel 718, Mater. Des., 2017, 134, p 139–150, https://doi.org/10.1016/j.matdes.2017.08.049. F. Geiger, K. Kunze, and T. Etter, Tailoring the Texture of IN738LC Processed by Selective Laser Melting (SLM) by Specific Scanning Strategies, Mater. Sci. Eng. A, 2016, 661, p 240–246, https://doi.org/10.1016/j.msea.2016.03.036.)). We propose an investigation of the effects of hatch spacing and layer thickness on microstructure development in laser powder bed fusion additive manufacturing. A Monte Carlo Potts model with textured solidification capabilities is used to study the effects of these parameters on a unidirectional scan strategy. The simulation results reveal substantial changes in grain morphology as well as texture. Additionally, EVP-FFT crystal plasticity simulations were performed to evaluate the effect of the microstructural shifts on mechanical response. The conclusions from this work elucidate the effects of these parameters on part microstructure as predicted by the texture-aware solidification Potts model and inform understanding of how bulk texture is predicted by the simulation approach.

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Simulation of Forming Process of Powder Bed for Additive Manufacturing

Journal of Manufacturing Science and Engineering ◽

10.1115/1.4032970 ◽

2016 ◽

Vol 138 (8) ◽

Cited By ~ 21

Author(s):

Zhaowei Xiang ◽

Ming Yin ◽

Zhenbo Deng ◽

Xiaoqin Mei ◽

Guofu Yin

Keyword(s):

Additive Manufacturing ◽

Coordination Number ◽

Layer Thickness ◽

Packing Density ◽

Size Distributions ◽

Forming Process ◽

Powder Bed ◽

Soft Sphere ◽

Number Increase ◽

Initial Packing

The forming process of powder bed for additive manufacturing (AM) is analyzed and is simplified to three processes, including random packing, layering, and compression. The processes are simulated by using the discrete element method (DEM). First, the particles with monosize, bimodal, and Gaussian size distributions are randomly packed. Then, the packed particles are layered with different thicknesses. Finally, a 20 μm compression is applied on the top surface of the layered powder beds. All the processes are simulated based on the soft sphere model. Packing density and coordination number are calculated to evaluate the packing mesostructure. The results indicate that the packing density and coordination number increase with the layer thickness increasing in the initial packing, and compression can effectively increase the density and coordination number of powder bed and decrease the effect of ranging layer thickness. The results also show that powder bed with monosize distribution initially has the best combination performance. Our research provides a theoretical guide to choosing the layer thickness and size distribution initially of powder bed for AM.

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