Analysis of the powder bed laser melting process for direct manufacturing of metallic components

2008 ◽  
Author(s):  
Pascal Aubry ◽  
Philippe Robert ◽  
Olivier Hercher
Keyword(s):  
Melting Process ◽  
Laser Melting ◽  
Powder Bed

Fundamentals of radiation heat transfer in AlSi10Mg powder bed during selective laser melting

2019 ◽  
Vol 25 (9) ◽  
pp. 1506-1515 ◽  
Author(s):  
Pei Wei ◽  
Zhengying Wei ◽  
Zhne Chen ◽  
Jun Du ◽  
Yuyang He ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Density ◽  
Negative Impact ◽  
Laser Energy ◽  
Melting Process ◽  
Laser Energy Density ◽  
Granular System ◽  
Laser Melting ◽  
Content Type ◽  
Powder Bed

Purpose This paper aims to study numerically the influence of the applied laser energy density and the porosity of the powder bed on the thermal behavior of the melt and the resultant instability of the liquid track. Design/methodology/approach A three-dimensional model was proposed to predict local powder melting process. The model accounts for heat transfer, melting, solidification and evaporation in granular system at particle scale. The proposed model has been proved to be a good approach for the simulation of the laser melting process. Findings The results shows that the applied laser energy density has a significantly influence on the shape of the molten pool and the local thermal properties. The relative low or high input laser energy density has the main negative impact on the stability of the scan track. Decreasing the porosity of the powder bed lowers the heat dissipation in the downward direction, resulting in a shallower melt pool, whereas pushing results in improvement in liquid track quality. Originality/value The randomly packed powder bed is calculated using discrete element method. The powder particle information including particle size distribution and packing density is taken into account in placement of individual particles. The effect of volumetric shrinkage and evaporation is considered in numerical model.

Finite Element Thermal Analysis of Melt Pool in Selective Laser Melting Process

2018 ◽  
Author(s):  
Zhibo Luo ◽  
Yaoyao Fiona Zhao
Keyword(s):  
Heat Source ◽  
Selective Laser Melting ◽  
Computational Cost ◽  
Melting Process ◽  
Point Heat Source ◽  
Laser Melting ◽  
Line Heat Source ◽  
Powder Bed ◽  
Melt Pool ◽  
Gaussian Point

Selective laser melting is one of the powder bed fusion processes which fabricates a part through layer-wised method. Due to the ability to build a customized and complex part, selective laser melting process has been broadly studied in academic and applied in industry. However, rapidly changed thermal cycles and extremely high-temperature gradients among the melt pool induce a periodically changed thermal stress in solidified layers and finally result in a distorted part. Therefore, the temperature distribution in the melt pool and the size and shape of the melt pool directly determine the mechanical and geometrical property of final part. As experimental trial-and-error method takes a huge amount of cost, different numerical methods have been adopted to estimate the transient temperature and thermal stress distribution in the melt pool and powder bed. The most existing research utilizes the moving Gaussian point heat source to model the profile of the melt pool, which consumes a significant amount of computational cost and cannot be used to implement the part-level simulation. This research proposes a new line heat source to replace the moving point heat source. Some efforts are applied to reduce the computational cost. Specifically, a relatively large step size is used for the line heat source to reduce the number of time steps. In addition, a mesh refinement scheme is adopted to reduce the number of cells in each time step by refining the mesh close to the heat source and coarsening the mesh far away from it. On the other hand, efforts are implemented to increase the accuracy of the simulation result. Temperature-dependent material properties are considered in this FE framework. In addition, material transition among powder, liquid, and solid are incorporated in the developed FE framework. In this study, temperature simulation of one scanning track based on self-developed FE code is applied for Stainless Steel 316L. The simulation results show that the temperature distribution and history of melt pool within line heat source are comparable to that of the moving Gaussian point heat source. While the simulation time is reduced by more than two times depending on the length of line heat input. Therefore, this FE model can be used to numerically investigate the process parameters and help to control the quality of the final part.

Optimizing quality of additively manufactured Inconel 718 using powder bed laser melting process

2016 ◽  
Vol 11 ◽  
pp. 60-70 ◽  
Author(s):  
Magda Sadowski ◽  
Leila Ladani ◽  
William Brindley ◽  
John Romano
Keyword(s):  
Inconel 718 ◽  
Melting Process ◽  
Laser Melting ◽  
Powder Bed

Numerical Simulation of Balling Phenomenon in Metallic Laser Melting Process

2016 ◽  
Author(s):  
Xin Liu ◽  
Mhamed Boutaous ◽  
Shihe Xin ◽  
Dennis Siginer
Keyword(s):  
Numerical Simulation ◽  
Selective Laser Sintering ◽  
Contact Process ◽  
Melting Process ◽  
Complex Model ◽  
Laser Melting ◽  
Powder Bed ◽  
Experimental Works ◽  
3D Numerical Model ◽  
Manufacturing Technologies

As well known, the selective laser Sintering (SLS) is one of the most modern and innovative additive manufacturing technologies with general advantages and wide applications, as a non-contact process, which is flexible, and easily controlled. The choice of process parameters is quite important for laser melting in metallic powder bed. When these parameters are not correctly chosen, particles are either not sintering at all or joining into rather large droplets. This process is named as balling phenomenon, which is extremely unfavorable. In this paper, a 3D numerical model based on discrete element method is proposed in order to study the effect of parameters on the generation of balling droplets in laser melting process. A complex model is developed which couples all phenomena of full SLS process and results of simulations are compared with experimental works of other researchers taken from the literature.

Thermal Behavior and Melt-Pool Dynamics of Cu-Cr-Zr Alloy in Powder-Bed Selective Laser Melting Process

2019 ◽  
Author(s):  
M. Shafiqur Rahman ◽  
Paul J. Schilling ◽  
Paul D. Herrington ◽  
Uttam K. Chakravarty
Keyword(s):  
Thermal Behavior ◽  
Selective Laser Melting ◽  
Melting Process ◽  
Rate Variation ◽  
Cfd Model ◽  
Laser Melting ◽  
Powder Bed ◽  
Melt Pool ◽  
Functional Components ◽  
Zr Alloy

Abstract Selective laser melting (SLM) is a growing additive manufacturing (AM) technology which is capable of rapidly fabricating functional components in the medical and aviation industries. The thermophysical properties and melt-pool dynamics involved in the powder-bed SLM process play a crucial role to determine the part quality and process optimization. In this study, a 3-D computational fluid dynamics (CFD) model with Cu-Cr-Zr (C-18150) powder-bed is developed incorporating a moving conical volumetric heat source and temperature-dependent thermal properties to conduct the Multiphysics simulations of the SLM process. The melt-pool dynamics and its thermal behavior are investigated numerically and results for temperature profile, cooling rate, variation in density, thermal conductivity, specific heat capacity, and velocity in the melt pool are obtained for different laser beam specifications. The validation of the CFD model is conducted by comparing the simulation results for temperature and the melt-front motion with the analytical results found from the classical Stefan problem of the phase-change material. Studying the process parameters, melt-pool geometry, and thermal behavior of Cu-Cr-Zr alloy can generate valuable information to establish Cu-Cr-Zr as a low-cost engineering material in the AM industry.

Characterization of Gas Atomized Ti-6Al-4V Powders for Additive Manufacturing

2018 ◽  
Vol 770 ◽  
pp. 3-8 ◽  
Author(s):  
Lerato Criselda Tshabalala ◽  
Ntombizodwa Mathe ◽  
Hilda Chikwanda
Keyword(s):  
Additive Manufacturing ◽  
Selective Laser Melting ◽  
Melting Process ◽  
Metal Powders ◽  
Laser Melting ◽  
Powder Bed ◽  
Geometrical Complexity ◽  
Powder Rheology ◽  
Titanium Powders ◽  
Powder Properties

In this paper, titanium powders from various sources were characterized to compare powder intergrity for additive manufacturing by selective laser melting process. Selective laser melting by powder-bed based Additive Manufacturing (AM) is an advanced manufacturing process that bonds successive layers of powder by laser melting to facilitate the creation of engineering components. This manufacturing approach facilitates the production of components with high geometrical complexity that would otherwise be impossible to create through conventional manufacturing processes. Although the use of powder in AM is quite common, powder production and optimization of powder properties to yield desired performance characteristics has posed a serious challenge to researchers. It is therefore critical that powder properties be studied and controlled to ensure reliability and repeatability of the components that are produced. Typically, the desired feature of high quality titanium metal powders for AM are a combination of high sphericity, density and flowability. Scanning electron microscopy, EDS, particle size distribution and powder rheology were extensively performed to investigate the properties of gas-atomized Ti-6Al-4V powders.

scholarly journals A novel physics-based and data-supported microstructure model for part-scale simulation of laser powder bed fusion of Ti-6Al-4V

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Jonas Nitzler ◽  
Christoph Meier ◽  
Kei W. Müller ◽  
Wolfgang A. Wall ◽  
N. E. Hodge
Keyword(s):  
Selective Laser Melting ◽  
Microstructure Evolution ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Laser Melting ◽  
Cooling Rates ◽  
Powder Bed ◽  
Proposed Model ◽  
Microstructure Model ◽  
Transformation Diagrams

AbstractThe elasto-plastic material behavior, material strength and failure modes of metals fabricated by additive manufacturing technologies are significantly determined by the underlying process-specific microstructure evolution. In this work a novel physics-based and data-supported phenomenological microstructure model for Ti-6Al-4V is proposed that is suitable for the part-scale simulation of laser powder bed fusion processes. The model predicts spatially homogenized phase fractions of the most relevant microstructural species, namely the stable $$\beta $$ β -phase, the stable $$\alpha _{\text {s}}$$ α s -phase as well as the metastable Martensite $$\alpha _{\text {m}}$$ α m -phase, in a physically consistent manner. In particular, the modeled microstructure evolution, in form of diffusion-based and non-diffusional transformations, is a pure consequence of energy and mobility competitions among the different species, without the need for heuristic transformation criteria as often applied in existing models. The mathematically consistent formulation of the evolution equations in rate form renders the model suitable for the practically relevant scenario of temperature- or time-dependent diffusion coefficients, arbitrary temperature profiles, and multiple coexisting phases. Due to its physically motivated foundation, the proposed model requires only a minimal number of free parameters, which are determined in an inverse identification process considering a broad experimental data basis in form of time-temperature transformation diagrams. Subsequently, the predictive ability of the model is demonstrated by means of continuous cooling transformation diagrams, showing that experimentally observed characteristics such as critical cooling rates emerge naturally from the proposed microstructure model, instead of being enforced as heuristic transformation criteria. Eventually, the proposed model is exploited to predict the microstructure evolution for a realistic selective laser melting application scenario and for the cooling/quenching process of a Ti-6Al-4V cube of practically relevant size. Numerical results confirm experimental observations that Martensite is the dominating microstructure species in regimes of high cooling rates, e.g., due to highly localized heat sources or in near-surface domains, while a proper manipulation of the temperature field, e.g., by preheating the base-plate in selective laser melting, can suppress the formation of this metastable phase.

scholarly journals Improving surface quality in selective laser melting based tool making

2021 ◽  
Author(s):  
Filippo Simoni ◽  
Andrea Huxol ◽  
Franz-Josef Villmer
Keyword(s):  
Surface Roughness ◽  
Additive Manufacturing ◽  
Surface Quality ◽  
Selective Laser Melting ◽  
Melting Process ◽  
Laser Remelting ◽  
Laser Melting ◽  
Great Cost ◽  
Starting Point ◽  
Processing Techniques

AbstractIn the last years, Additive Manufacturing, thanks to its capability of continuous improvements in performance and cost-efficiency, was able to partly replace and redefine well-established manufacturing processes. This research is based on the idea to achieve great cost and operational benefits especially in the field of tool making for injection molding by combining traditional and additive manufacturing in one process chain. Special attention is given to the surface quality in terms of surface roughness and its optimization directly in the Selective Laser Melting process. This article presents the possibility for a remelting process of the SLM parts as a way to optimize the surfaces of the produced parts. The influence of laser remelting on the surface roughness of the parts is analyzed while varying machine parameters like laser power and scan settings. Laser remelting with optimized parameter settings considerably improves the surface quality of SLM parts and is a great starting point for further post-processing techniques, which require a low initial value of surface roughness.

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