scholarly journals Simulation of Stress Field during the Selective Laser Melting Process of the Nickel-Based Superalloy, GH4169

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1525 ◽  
Author(s):  
Zhanyong Zhao ◽  
Liang Li ◽  
Le Tan ◽  
Peikang Bai ◽  
Jing Li ◽  
...  
Keyword(s):  
Tensile Stress ◽  
Compressive Stress ◽  
Selective Laser Melting ◽  
Thermal Strain ◽  
Melting Process ◽  
Laser Melting ◽  
Nickel Based Superalloy ◽  
Melt Pool ◽  
Scanning Line ◽  
Melting And Solidification

In this paper, GH4169 alloy’s distributions of temperature and stress during the selective laser melting (SLM) process were studied. The SLM process is a dynamic process of rapid melting and solidification, and we found there were larger temperature gradients near the turning of scan direction and at the overlap of the scanning line, which produced thermal strain and stress concentration and gave rise to warping deformations. The stresses increased as the distance became further away from the melt pool. There was tensile stress in the most-forming zones, but compressive stress occurred near the melt pool area. When the parts were cooled to room temperature after the SLM process, tensile stress was concentrated around the parts’ boundaries. Residual stress along the z direction caused the warping deformations, and although there was tensile stress in the parts’ surfaces, but there was compressive stress near the substrate.

Numerical Investigation of Selective Laser Melting Process for 904L Stainless Steel

2012 ◽  
Author(s):  
Miranda Fateri ◽  
Andreas Gebhardt ◽  
Maziar Khosravi
Keyword(s):  
Heat Flux ◽  
Stainless Steel ◽  
Selective Laser Melting ◽  
Melting Process ◽  
Full Density ◽  
Laser Melting ◽  
Scanning Velocity ◽  
Selective Laser Melting Process ◽  
Fine Mesh ◽  
Melt Pool

Selective Laser Melting process (SLM) is an important manufacturing method for producing complex geometries which allows for creation of full density parts with similar properties as the bulk material without extensive post processing. In SLM process, laser power, beam focus diameter, and scanning velocity must be precisely set based on the material properties in order to produce dense parts. In this study, Finite Element Analysis (FEA) method is employed in order to simulate and analyze a single layer of 904L Stainless Steel. A three-dimensional transient thermal model of the SLM process based on phase change enthalpy, irradiation scattering, and heat conductivity of powder is developed. The laser beam is modeled as a moving heat flux on the surface of the layer using a fine mesh which allows for a variation of the shape and distribution of the beam. In this manner, various Gaussian distributions are investigated and compared against single and multi-element heat flux sources. The melt pool and temperature distribution in the part are numerically investigated in order to determine the effects of varying laser intensity, scanning velocity as well as preheating temperature. The results of the simulation are verified by comparing the melt pool width as a function of power and velocity against the experimentally obtained results. Lastly, 3D objects are fabricated with a SLM 50 Desktop machine using the acquired optimized process parameters.

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.

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.

scholarly journals A Computational Model of Melt Pool Morphology for Selective Laser Melting Process

2021 ◽  
Author(s):  
Kai Guo ◽  
Lihong Qiao ◽  
Zhicheng Huang ◽  
Nabil Anwer ◽  
Yuda Cao
Keyword(s):  
Computational Model ◽  
Selective Laser Melting ◽  
Process Parameters ◽  
Melting Process ◽  
Laser Melting ◽  
Synthetic Process ◽  
Part Geometry ◽  
Melt Pool ◽  
Proposed Model ◽  
High Consistency

Abstract Selective laser melting (SLM) is a promising metal additive manufacturing technology, which holds widespread applications in numerous fields. Unfortunately, it is arduous to predict the real SLM part geometry, which impedes its further development. While the morphology of melt pool, influenced and determined by process parameters, poses a crucial influence on the overall part geometry. Nonetheless, the association between process parameters and melt pool morphology is still unclear. Hence it is indispensable to explore relevant solution to address this issue. For this purpose, this paper proposes a new model to directly establish the mathematical relationship between process parameters and melt pool structure for SLM process. In this model, the status of melt pool is first qualitatively analyzed via the defined synthetic process index, and three types of melting states are differentiated including low melting, intermediate melting and high melting, which could cover different melt pool modes. Then, the computational model involving more physical mechanisms integrating mass conversion, heat exchange and temperature field is constructed. Melt pool critical geometries including the height, width, depth and length could be computed through the model. In order to validate the correctness of the proposed model, published experimental observations and existing models are compared. Calculation results from the proposed model show high consistency with the experimental samples and better accuracy than existing empirical models. Its applicability in melt pool classification and prediction is also verified, laying foundation for geometric simulation of SLM object which is successively shaped melt-pool by melt-pool.

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.

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