scholarly journals Modelling of Selective Laser Melting Process of Quartz Glass at Elevated Temperatures

2021 ◽  
Vol 248 ◽  
pp. 01001
Author(s):  
M.A. Gridnev ◽  
R.S. Khmyrov ◽  
A.V. Gusarov
Keyword(s):  
Selective Laser Melting ◽  
Quartz Glass ◽  
Elevated Temperatures ◽  
Melting Process ◽  
Coupled Processes ◽  
Powder Layer ◽  
Layer By Layer ◽  
Laser Melting ◽  
Material Quality ◽  
Powder Consolidation

Selective laser melting (SLM) to date is the method of additive manufacturing allowing fabricating products from powder layer-by-layer according to a 3D model. However, when applying this method to fragile materials, parts crack while fabricating due to high temperatures. Quartz glass is a promising material for fabricating products by SLM without cracks due to a low thermal expansion. However, quality of fabricated material differs from the fused cast ones. This article aims to test the method of SLM with preheating to improve the material quality. Experiments on single track formation in SLM are analysed by modelling the coupled processes of heat transfer and powder consolidation in the laser-interaction zone. The mathematical model is validated by the experiments. It is shown that the preheating can improve the material quality and increase the process productivity but overheating may result in undesirable crystallization.

Numerical Study of Porosity Formation With Implementation of Laser Multiple Reflection in Selective Laser Melting

2019 ◽  
Author(s):  
Bo Cheng ◽  
Charles Tuffile
Keyword(s):  
Selective Laser Melting ◽  
Laser Scanning ◽  
Numerical Study ◽  
Fluid Model ◽  
Melting Process ◽  
Scanning Speed ◽  
Powder Layer ◽  
Cfd Model ◽  
Laser Melting ◽  
Porosity Formation

Abstract In selective laser melting (SLM) process, the build part quality is determined by process parameters such as laser scanning speed and power. The presence of porosity, a major printing defect that significantly affects part performance, may arise in laser melting process due to insufficient or excess energy input. The improvement of build quality heavily depends on fundamental understanding of porosity formation in the SLM process. In this study, the discrete element method (DEM) has been utilized to simulate the creation of a newly deposited powder layer. A computational fluid dynamics (CFD) model was developed to simulate the melting and solidification process of Ti-6Al-4V powders in the SLM process. The thermo-fluid model includes effect of surface tension and recoil pressure as well as laser ray multi-reflection in keyhole. The predictability of the developed CFD model has been validated against literature experimental data. It is found that the collapse of an unstable deep keyhole was responsible for the formation of pores. In addition, higher laser scanning speeds tend to form unstable melt pools, e.g., melt pool break-up.

Optimizing the process parameters for additive manufacturing of glass components by selective laser melting: Soda-lime glass versus quartz glass

2021 ◽  
pp. 1-10
Author(s):  
Sergey Grigoriev ◽  
Roman Khmyrov ◽  
Mikhail Gridnev ◽  
Tatiana Tarasova ◽  
Andrey Gusarov
Keyword(s):  
Additive Manufacturing ◽  
Selective Laser Melting ◽  
Quartz Glass ◽  
Soda Lime ◽  
High Viscosity ◽  
Residual Porosity ◽  
Soda Lime Glass ◽  
Laser Melting ◽  
Powder Consolidation ◽  
Preheating Temperature

Abstract Additive manufacturing by selective laser melting (SLM) is generally applicable to glasses while insufficient resistance of the material to thermal shocks due to local laser heating may result in cracking and a high viscosity of glass melt is responsible for incomplete powder consolidation related to residual porosity. The present work shows that preheating up to 350 °C is sufficient to avoid cracking of soda-lime glass. Preheating of quartz glass up to 730 °C considerably decreases the residual porosity, which is explained by acceleration of powder consolidation by the viscous-flow mechanism of glass particles' coalescence. Variation of the preheating temperature is an effective tool to control consolidation of glass powder and to avoid cracking.

scholarly journals Printability and Microstructure of Selective Laser Melting of WC/Co/Cr Powder

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2397 ◽  
Author(s):  
Sabina Luisa Campanelli ◽  
Nicola Contuzzi ◽  
Paolo Posa ◽  
Andrea Angelastro
Keyword(s):  
Selective Laser Melting ◽  
Complex Geometry ◽  
Melting Process ◽  
Powder Layer ◽  
Laser Melting ◽  
Heterogeneous Distribution ◽  
High Melting Temperature ◽  
Hardness Tests ◽  
Small Cracks ◽  
Melting And Solidification

The selective laser melting process is a growing technology for the manufacture of parts with very complex geometry. However, not all materials are suitable for this process, involving rapid localized melting and solidification. Tungsten has difficulties due to the high melting temperature. This study focuses on the possibility of processing a WC/Co/Cr composite powder using selective laser melting. Samples were fabricated and characterized in terms of density, defects, microstructure and hardness. Tests were conducted with hatch spacing of 120 μm and process speed of 40 mm/s. A constant laser power of 100 W and a powder layer thickness of 30 μm were used. A relative density of 97.53%, and therefore a low porosity, was obtained at an energy density of 12.5 J/mm2. Microscopic examination revealed the presence of small cracks and a very heterogeneous distribution of the grain size.

Microstructure Characterization of AlSi10Mg Fabricated by Selective Laser Melting Process

2018 ◽  
Vol 941 ◽  
pp. 1437-1442
Author(s):  
Takashi Maeshima ◽  
Keiichiro Oh-Ishi ◽  
Hiroaki Kadoura ◽  
Masashi Hara
Keyword(s):  
Selective Laser Melting ◽  
Molten Pool ◽  
Three Dimensional ◽  
Melting Process ◽  
Powder Layer ◽  
Base Temperature ◽  
Fish Scale ◽  
Laser Melting ◽  
Microstructure Observation ◽  
Three Dimensional Finite Element

Multi-scale microstructure observation and three dimensional finite element thermal analysis of AlSi10Mg alloy fabricated by selective laser melting (SLM) process were demonstrated in order to understand the microstructure formation process during SLM fabrication. The unique hierarchically microstructures were observed: (1) the “fish scale” microstructure corresponding to a part of molten pool consists of columnar and equiaxed grains and (2) these grains contain a substructure of α-Al surrounded by Si particles. It is revealed that a supersaturated Si concentration due to the predicted rapid cooling rate on the order of 106 oC/s. In addition, the base temperature during the fabrication increases gradually with some peak temperature of each laser path as the laser scan has proceeded on a powder layer. Although the thermal changes cause no melting of the AlSi10Mg except directly fused region by selective laser so called molten pool, those are capable of causing precipitation and/or clustering.

scholarly journals Numerical-Experimental Study of the Consolidation Phenomenon in the Selective Laser Melting Process with a Thermo-Fluidic Coupled Model

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1414 ◽  
Author(s):  
Francisco Cordovilla ◽  
Ángel García-Beltrán ◽  
Miguel Garzón ◽  
Diego Muñoz ◽  
José Ocaña
Keyword(s):  
Selective Laser Melting ◽  
Coupled Model ◽  
Melting Process ◽  
Metallic Powder ◽  
Added Value ◽  
Limiting Factors ◽  
Powder Layer ◽  
Laser Melting ◽  
Selective Laser Melting Process ◽  
Eulerian Formulation

One of the main limiting factors for a widespread industrial use of the Selective Laser Melting Process it its lack of productivity, which restricts the use of this technology just for high added-value components. Typically, the thickness of the metallic powder that is used lies on the scale of micrometers. The use of a layer up to one millimeter would be necessarily associated to a dramatic increase of productivity. Nevertheless, when the layer thickness increases, the complexity of consolidation phenomena makes the process difficult to be governed. The present work proposes a 3D finite element thermo-coupled model to study the evolution from the metallic powder to the final consolidated material, analyzing specifically the movements and loads of the melt pool, and defining the behavior of some critical thermophysical properties as a function of temperature and the phase of the material. This model uses advanced numerical tools such as the Arbitrary Lagrangean–Eulerian formulation and the Automatic Remeshing technique. A series of experiments have been carried out, using a high thickness powder layer, allowing for a deeper understanding of the consolidation phenomena and providing a reference to compare the results of the numerical calculations.

A Powder Shrinkage Model for Describing Real Layer Thickness during Selective Laser Melting Process

2010 ◽  
Vol 97-101 ◽  
pp. 3820-3823 ◽  
Author(s):  
Dan Qing Zhang ◽  
Qi Zhou Cai ◽  
Jin Hui Liu ◽  
Rui Di Li
Keyword(s):  
Layer Thickness ◽  
Metal Powder ◽  
Selective Laser Melting ◽  
Melting Process ◽  
Powder Layer ◽  
Laser Melting ◽  
Selective Laser Melting Process ◽  
Mathematical Explanations ◽  
Total Shrinkage ◽  
Initial Layers

Shrinkage tends to generate when loose metal powder melted in each processing layer along the direction of layer growing during selective laser melting process, resulting in an increased real layer thickness. The shrinkage model for layer shrinkage in SLM process is established. The variation of real layer thickness and the relevant mathematical explanations are discussed in this paper. The results show that the total shrinkage of metal powder layer sharply increases in the initial layers, and then reaches to a plateau value with the increased processing layers. This value is defined by the ratio of sliced layer thickness (h) to relative density (k) during selective laser melting process.

Inverse Thermal Analysis of Melting Pool in Selective Laser Melting Process

2015 ◽  
Vol 651-653 ◽  
pp. 1519-1524 ◽  
Author(s):  
Laurent van Belle ◽  
Alban Agazzi
Keyword(s):  
Heat Source ◽  
Residual Stresses ◽  
Selective Laser Melting ◽  
Selective Laser Sintering ◽  
Solid Material ◽  
Melting Process ◽  
Layer By Layer ◽  
Laser Melting ◽  
Mechanical Modelling ◽  
Melting Pool

The Selective Laser Melting (SLM) process of metallic powder is an additive technology. It allows the production of complex-shaped parts which are difficult to obtain by conventional methods. The principle is similar to Selective Laser Sintering (SLS) process: it consists, from an initial CAD model, to create the desired part layer by layer. The laser scans a powder bed of 40 μm thick. The irradiated powder is instantly melted and becomes a solid material when the laser moves away. A new layer of powder is left and the laser starts a new cycle of scanning. The sudden and intense phase changing involves high thermal gradients which induce contraction and expansion cycles in the part. These cycles results in irreversible plastic strains. The presence of residual stresses in the manufactured part can damage the mechanical properties, such as the fatigue life. This study focuses on the thermal and mechanical modelling of the SLM process. One of the key points of the mechanical modelling is the determination of the heat source generated by the laser in order to predict residual stresses. This work is divided in three parts. In a first part, an experimental protocol is established in order to measure the temperature variation during the process. In the second part, a thermal model of the process is proposed. Finally, an inverse method to determine the power and the shape of the heat source is developed. Experimental and computational results are fitted. The influence of several geometries of the heat source is investigated.

Three-Dimensional Temperature Gradient Mechanism in Selective Laser Melting of Ti-6Al-4V

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
C. H. Fu ◽  
Y. B. Guo
Keyword(s):  
Temperature Gradient ◽  
Selective Laser Melting ◽  
Molten Pool ◽  
Three Dimensional ◽  
Melting Process ◽  
Layer By Layer ◽  
Laser Melting ◽  
Transient Nature ◽  
Melting Pool ◽  
Three Dimensional Finite Element

Selective laser melting (SLM) is widely used in making three-dimensional functional parts layer by layer. Temperature magnitude and history during SLM directly determine the molten pool dimensions and surface integrity. However, due to the transient nature and small size of the molten pool, the temperature gradient and the molten pool size are challenging to measure and control. A three-dimensional finite element (FE) simulation model has been developed to simulate multilayer deposition of Ti-6Al-4 V in SLM. A physics-based layer buildup approach coupled with a surface moving heat flux was incorporated into the modeling process. The melting pool shape and dimensions were predicted and experimentally validated. Temperature gradient and thermal history in the multilayer buildup process was also obtained. Furthermore, the influences of process parameters and materials on the melting process were evaluated.

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