scholarly journals Formation of SS316L Single Tracks in Micro Selective Laser Melting: Surface, Geometry, and Defects

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Zhiheng Hu ◽  
Balasubramanian Nagarajan ◽  
Xu Song ◽  
Rui Huang ◽  
Wei Zhai ◽  
...  
Keyword(s):  
Selective Laser Melting ◽  
Process Parameters ◽  
Molten Pool ◽  
Fine Powder ◽  
Spot Size ◽  
Powder Size ◽  
Surface Geometry ◽  
Laser Melting ◽  
Scanning Velocity ◽  
Melting Surface

To fabricate complex parts with a fine resolution and smooth finish, micro selective laser melting (SLM) has been developed recently by combining three attributes: small laser beam spot, fine powder size, and thin layer thickness. This paper studies the effect of the micro-SLM process parameters on the single track formation of 316L stainless steel. The surface morphology, geometrical features, and defects have been analyzed in detail. The results highlight that laser power and scanning velocity have a significant effect on the formation of single tracks. The single tracks fabricated through micro-SLM with varying process parameters are classified into four types: no melting, discontinuous, continuous but unstable, and continuous tracks. Besides, the top surface of the tracks is observed with “double-crest” morphology, due to the high recoil pressure gradient generated by the extremely fine spot size. In addition, molten pool geometry (width, depth, and height) has been characterized to study the mode of the molten pool in micro-SLM. Finally, the occurrence of two typical defects within the tracks, keyhole pore and cavity at the edges, has been studied.

scholarly journals The Influence of Process Parameters and Scanning Strategy on Lower Surface Quality of TA15 Parts Fabricated by Selective Laser Melting

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1228
Author(s):  
Junjie Jiang ◽  
Jianming Chen ◽  
Zhihao Ren ◽  
Zhongfa Mao ◽  
Xiangyu Ma ◽  
...  
Keyword(s):  
Surface Quality ◽  
Selective Laser Melting ◽  
Process Parameters ◽  
Flexible Manufacturing ◽  
Molten Pool ◽  
Lower Surface ◽  
Laser Melting ◽  
Scanning Strategy ◽  
Influence Of Process Parameters

With superior flexible manufacturing capability, selective laser melting (SLM) has attracted more and more attention in the aerospace, medical, and automotive industries. However, the poor quality of the lower surface in overhanging structures is still one of the factors that limits the wide application of SLM. In this work, the influence of process parameters and scanning strategy on the lower surface quality of SLMed TA15 (Ti-6Al-2Zr-1Mo-1V) titanium alloy parts were studied. The results showed that the laser surface energy density (EF) had a significant influence on the quality of the lower surface. Excessive EF led to obvious sinking of the molten pool and a serious slag hanging phenomenon. However, the too low EF easily contributed to the insufficient powder fusion in the lower surface area, which led to the agglomeration of a molten pool during core processing, resulting in slag hanging, pores, and powder spalling that reduced the quality of the lower surface. Moreover, the cross-remelting strategy and non-remelting strategy gained better surface quality at the low EF and high EF, respectively. In addition, it was found that the quality of the lower surface could be quickly and accurately evaluated by the cooling time of the molten pool during the processing of the lower surface. This research can increase the understanding of the forming mechanism of the lower surface and has certain guiding significance for the process optimization of the lower surface.

scholarly journals Numerical Simulation of Moving Heat Flux during Selective Laser Melting of AlSi25 Alloy Powder

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 877
Author(s):  
Cong Ma ◽  
Xianshun Wei ◽  
Biao Yan ◽  
Pengfei Yan
Keyword(s):  
Numerical Simulation ◽  
Selective Laser Melting ◽  
Process Parameters ◽  
Molten Pool ◽  
Laser Power ◽  
Scanning Speed ◽  
Powder Layer ◽  
Maximum Temperature ◽  
Three Dimensional Model ◽  
Laser Melting

A single-layer three-dimensional model was created to simulate multi-channel scanning of AlSi25 powder in selective laser melting (SLM) by the finite element method. Thermal behaviors of laser power and scanning speed in the procedure of SLM AlSi25 powder were studied. With the increase of laser power, the maximum temperature, size and cooling rate of the molten pool increase, while the scanning speed decreases. For an expected SLM process, a perfect molten pool can be generated using process parameters of laser power of 180 W and a scanning speed of 200 mm/s. The pool is greater than the width of the scanning interval, the depth of the molten pool is close to scan powder layer thickness, the temperature of the molten pool is higher than the melting point temperature of the powder and the parameters of the width and depth are the highest. To confirm the accuracy of the simulation results of forecasting excellent process parameters, the SLM experiment of forming AlSi25 powder was carried out. The surface morphology of the printed sample is intact without holes and defects, and a satisfactory metallurgical bond between adjacent scanning channels and adjacent scanning layers was achieved. Therefore, the development of numerical simulation in this paper provides an effective method to obtain the best process parameters, which can be used as a choice to further improve SLM process parameters. In the future, metallographic technology can also be implemented to obtain the width-to-depth ratio of the SLM sample molten pool, enhancing the connection between experiment and theory.

scholarly journals Effect of Selective Laser Melting Process Parameters on Microstructure and Properties of Co-Cr Alloy

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1546 ◽  
Author(s):  
Jian-Hong Wang ◽  
Jie Ren ◽  
Wei Liu ◽  
Xiao-Yu Wu ◽  
Ming-Xiang Gao ◽  
...  
Keyword(s):  
Selective Laser Melting ◽  
Process Parameters ◽  
Molten Pool ◽  
Laser Energy ◽  
Melting Process ◽  
Chromium Alloy ◽  
Cobalt Chromium ◽  
Laser Melting ◽  
The Relationship ◽  
Cobalt Chromium Alloy

Due to the rapid melting and solidification mechanisms involved in selective laser melting (SLM), CoCrMo alloys fabricated by SLM differ from the cast form of the same alloy. In this study, the relationship between process parameters and the morphology and macromechanical properties of cobalt-chromium alloy micro-melting pools is discussed. By measuring the width and depth of the molten pool, a theoretical model of the molten pool is established, and the relationship between the laser power, the scanning speed, the scanning line spacing, and the morphology of the molten pool is determined. At the same time, this study discusses the relationship between laser energy and molding rate. Based on the above research, the optimal process for the laser melting of cobalt-chromium alloy in the selected area is obtained. These results will contribute to the development of biomedical CoCr alloys manufactured by SLM.

An integrated analytical model for the forecasting of the molten pool dimensions in Selective Laser Melting

Laser Physics ◽  
2021 ◽  
Vol 32 (2) ◽  
pp. 026001
Author(s):  
Andrea Angelastro ◽  
Sabina Luisa Campanelli
Keyword(s):  
Selective Laser Melting ◽  
Analytical Model ◽  
Process Parameters ◽  
Molten Pool ◽  
Complex Geometry ◽  
Physical Factors ◽  
Laser Melting ◽  
Wide Range ◽  
Optimal Forecasting ◽  
Stress And Deformation

Abstract Selective laser melting (SLM) is one of the most promising processes in the Additive Manufacturing of metals because of the possibility to fabricate complex geometry parts with a wide range of materials. The molten pool dimensions are notoriously crucial for the production of high quality parts, in terms of mechanical properties and roughness, and to control the ‘balling’ phenomenon. In the past, several studies have been conducted to monitor temperature gradient and thermal history, stress and deformation field, balling occurrence, effect of volume shrinkage and the effect of process parameters on temperature evolution. Up to now, very few works are available in literature on the effects of the process parameters on the molten pool shape and dimensions: moreover, they also neglect the simultaneously effect of various physical factors. In this work, an integrated analytical model, consisting of three sub-models (thermal, optical and melting sub-models), with the purpose to forecast the molten pool dimensions in terms of width and depth, was developed. An experimental plan has been carried out, processing the 18 maraging 300 steel, to demonstrate the capability and the accuracy of the presented model. The obtained results demonstrate that the integrated analytical model led to optimal forecasting.

Simulation Informed Effects of Solidification Rate on 316L Single Tracks Produced by Selective Laser Melting

2020 ◽  
Author(s):  
A. L. K. Rawlings ◽  
A. J. Birnbaum ◽  
J. G. Michopoulos ◽  
J. C. Steuben ◽  
A. P. Iliopoulos ◽  
...  
Keyword(s):  
Selective Laser Melting ◽  
Process Parameters ◽  
Solidification Rate ◽  
Interface Velocity ◽  
Processing Parameters ◽  
Spot Size ◽  
Grain Structure ◽  
Material System ◽  
Laser Melting ◽  
Specific Material

Abstract The formation of sub-grain cellular structures generated during the rapid solidification associated with selective laser melting (SLM) typically yields enhanced mechanical properties in terms of yield stress without considerable loss in ductility when compared with those of wrought material. The extent to which the sub-grain structure appears under standard metallographic preparation shows dependence on multiple systematic conditions. This study identifies the effects of solidification and cooling rate on the grain and sub-grain structure in stainless steel through varying the processing parameters (laser power, scan velocity and spot size) of single tracks on both as-received, small grain and annealed, giant grain substrates. The process parameters, in conjunction with the initial substrate microstructure, are key components in understanding the resulting microstructure. Process parameters, particularly scan velocity, dictate the solidification rate and primary regrowth directions while the initial microstructure and its thermomechanical history dictate the propensity for stored strain energy density. Modeling the thermal process allows for experimental analysis within the context of predicted location within processing space as it pertains to local interface velocity and temperature gradient. Furthermore, it highlights the fact that this specific material system behaves in a manner that is inconsistent with classical solidification theory.

scholarly journals Simulation of the Evolution of Thermal Dynamics during Selective Laser Melting and Experimental Verification Using Online Monitoring

Sensors ◽  
2020 ◽  
Vol 20 (16) ◽  
pp. 4451
Author(s):  
Peiying Bian ◽  
Xiaodong Shao ◽  
Jingli Du ◽  
Fangxia Ye ◽  
Xiuping Zhang ◽  
...  
Keyword(s):  
Selective Laser Melting ◽  
Process Parameters ◽  
Molten Pool ◽  
High Speed ◽  
Online Monitoring ◽  
Simulation Method ◽  
Technological Parameters ◽  
Laser Melting ◽  
Thermal Dynamics ◽  
Pool Formation

The process parameters of selective laser melting (SLM) significantly influence molten pool formation. A comprehensive understanding and analysis, from a macroscopic viewpoint, of the mechanisms underlying these technological parameters and how they affect the evolution of molten pools are presently lacking. In this study, we established a dynamic finite element simulation method for the process of molten pool formation by SLM using a dynamic moving heat source. The molten pool was generated, and the dynamic growth process of the molten pool belt and the evolution process of the thermal field of the SLM molten pool were simulated. Then, a deposition experiment that implemented a new measurement method for online monitoring involving laser supplementary light was conducted using the same process parameters as the simulation, in which high-speed images of the molten pool were acquired, including images of the pool surface and cross-section images of the deposited samples. The obtained experimental results show a good agreement with the simulation results, demonstrating the effectiveness of the proposed algorithm.

Analysis of Selective Laser Melting Process Parameters Effect on Mechanical and Material Properties for Stainless Steel 316L

2016 ◽  
Vol 258 ◽  
pp. 579-582
Author(s):  
Pavlína Trubačová ◽  
Miroslav Piska ◽  
Jana Horníková ◽  
Pavel Šandera ◽  
Karel Slámečka
Keyword(s):  
Mechanical Properties ◽  
Selective Laser Melting ◽  
Process Parameters ◽  
Melting Process ◽  
Material Behavior ◽  
Process Conditions ◽  
Stainless Steel 316L ◽  
Laser Melting ◽  
Scanning Velocity ◽  
Focus Plane

This paper deals with a testings of the Selective Laser Melting (SLM) process parameters on mechanical properties, material behavior, surface quality and on machinability of austenitic steel 316L. The SLM process conditions were changed to assess their effect on mechanical properties of the sintered material measured in tensile testing. The laser power, the scanning velocity of laser beam, the layer thickness and the laser focus plane were set to find the most appropriate set of process parameters to obtain the mechanical properties of parts.

Effects of Powder Characteristics on Selective Laser Melting of 316L Stainless Steel Powder

2011 ◽  
Vol 189-193 ◽  
pp. 3664-3667 ◽  
Author(s):  
Sheng Zhang ◽  
Qing Song Wei ◽  
Guang Ke Lin ◽  
Xiao Zhao ◽  
Yu Sheng Shi
Keyword(s):  
Stainless Steel ◽  
Selective Laser Melting ◽  
316L Stainless Steel ◽  
Fine Powder ◽  
Steel Powder ◽  
Laser Melting ◽  
Broad Size Distribution ◽  
Lower Oxygen ◽  
Powder Characteristics ◽  
Loose Powder

316L stainless steel parts were manufactured via selective laser melting . This work stu- dies the effects of powder characteristics such as particle size and particle shape composition on the density. It shows that the powder with a broad size distribution and using spherical fine powder can lead to an increase in the density of the loose powder and thus the densification of the laser melted powder. The aerosol powder forms parts of lower oxygen content well, and the density can reach to 90%.

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