scholarly journals Selective Laser Melting Strategy for Fabrication of Thin Struts Usable in Lattice Structures

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1763 ◽  
Author(s):  
Radek Vrána ◽  
Daniel Koutný ◽  
David Paloušek ◽  
Libor Pantělejev ◽  
Jan Jaroš ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Selective Laser Melting ◽  
Laser Scanning ◽  
Laser Energy ◽  
Lattice Structure ◽  
Processing Parameters ◽  
Laser Melting ◽  
Contour Lines ◽  
Lower Porosity ◽  
Linear Laser

This paper deals with the selective laser melting (SLM) processing strategy for strut-lattice structure production which uses only contour lines and allows the porosity and roughness level to be managed based on combination of the input and linear energy parameters. To evaluate the influence of a laser scanning strategy on material properties and surface roughness a set of experiments was performed. The single welds test was used to find the appropriate processing parameters to achieve continuous welds with known width. Strut samples were used to find a suitable value of weld overlapping and to clarify the influence of input and linear laser energy on the strut porosity and surface roughness. The samples of inclined hollow struts were used to compare the wall thickness with single welds width; the results showed about 25% wider welds in the case of a hollow strut. Using the proposed SLM strategy it is possible to reach a significantly lower porosity and surface roughness of the struts. The best results for struts with an inclination of 35.26° were achieved with 25% track overlapping, input energy in the range from 9 J to 10.5 J and linear energy Elin from 0.25 to 0.4 J/mm; in particular, the relative density of 99.83% and the surface roughness on the side of the strut of Ra 14.6 μm in an as-built state was achieved.

scholarly journals Collaborative Optimization on Density and Surface Roughness of 316L Stainless Steel in Selective Laser Melting

2020 ◽  
Author(s):  
Yong Deng ◽  
Zhongfa Mao ◽  
Nan Yang ◽  
Xiaodong Niu ◽  
Xiangdong Lu
Keyword(s):  
Surface Roughness ◽  
Stainless Steel ◽  
Relative Density ◽  
Selective Laser Melting ◽  
Laser Power ◽  
316L Stainless Steel ◽  
Scanning Speed ◽  
Processing Parameters ◽  
Collaborative Optimization ◽  
Laser Melting

Although the concept of additive manufacturing has been proposed for several decades, momentum of selective laser melting (SLM) is finally starting to build. In SLM, density and surface roughness, as the important quality indexes of SLMed parts, are dependent on the processing parameters. However, there are few studies on their collaborative optimization in SLM to obtain high relative density and low surface roughness simultaneously in the previous literature. In this work, the response surface method was adopted to study the influences of different processing parameters (laser power, scanning speed and hatch space) on density and surface roughness of 316L stainless steel parts fabricated by SLM. The statistical relationship model between processing parameters and manufacturing quality is established. A multi-objective collaborative optimization strategy considering both density and surface roughness is proposed. The experimental results show that the main effects of processing parameters on the density and surface roughness are similar. It is noted that the effects of the laser power and scanning speed on the above objective quality show highly significant, while hatch space behaves an insignificant impact. Based on the above optimization, 316L stainless steel parts with excellent surface roughness and relative density can be obtained by SLM with optimized processing parameters.

Effects of Parameters on Surface Roughness of Metal Parts by Selective Laser Melting

2013 ◽  
Vol 834-836 ◽  
pp. 872-875 ◽  
Author(s):  
Qun Qin ◽  
Guang Xia Chen
Keyword(s):  
Surface Roughness ◽  
Power Density ◽  
Selective Laser Melting ◽  
Laser Power ◽  
Processing Parameters ◽  
Laser Power Density ◽  
Laser Melting ◽  
Scanning Velocity ◽  
Metal Parts ◽  
Overlap Ratio

The primary goal of this research is the effects of laser process parameters on surface roughness of metal parts built by selective laser melting. The main processing parameters used to control the surface roughness of melted layers are laser power, scanning velocity and overlap ratio. In our work, an orthogonal experimental design was employed to find the changing rules of the surface roughness through changing SLM processing parameters. The results show that the overlap ratio is the most important factor to affect the surface roughness. When the overlap ratio is below 50%, the surface roughness value of melted layers will decrease with laser power density increasing. When the overlap ratio is higher than or equal to 50%, the surface roughness value increases with the laser power density increasing. The optimal parameters of laser power 143W, scanning velocity 5m/min and overlap ratio 30% can be used to achieve melted layers with the best surface quality in our experiments, and the roughness value increases with slicing thickness increasing and the surface bias angle decreases.

scholarly journals Formability, Microstructure and Properties of Inconel 718 Superalloy Fabricated by Selective Laser Melting Additive Manufacture Technology

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 991
Author(s):  
Xiaoping Liu ◽  
Kuaishe Wang ◽  
Ping Hu ◽  
Xiaomei He ◽  
Baicheng Yan ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Selective Laser Melting ◽  
Inconel 718 ◽  
Laser Scanning ◽  
Laser Energy ◽  
High Surface ◽  
Additive Manufacture ◽  
Internal Cavity ◽  
Laser Melting ◽  
Manufacture Technology

Many urgently needed inconel superalloy parts with complex internal cavity geometry and high surface precision are difficult to prepare by traditional subtractive manufacturing methods because of its poor machinability. The additive manufacturing technology that has emerged in recent years became a research hotspot in the manufacture of refractory and difficult-to-process metals. In the present study, selective laser melting (SLM), a typical additive manufacture technology, was used to prepare Inconel 718 samples. The influences of input laser energy density ((E, J/mm3) on densification behavior, phases composition, microstructures, microhardness, and wear performance of the SLM as-built Inconel 718 samples were explored in detail. X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to examine the phase composition and microstructure evolutions. The results show that the formablity, microstructures and mechanical properties of the printed samples were all improved with the increase of E within the parameter setting range of this study. At a lower E, the poor surface morphology and balling effect occurred, the density, hardness, and wear resistance were all at a relatively lower level. When an E value of 190 J/mm was properly set, the surface open-pores and balling effect disappeared, the laser scanning tracks became smooth and continuous, the near-full dense (99.15%) and specimens with good metallurgical bonding and no critical defect were obtained, in which the average microhardness value reached 348 HV0.2 and wear rate was 5.67 × 10−4 mm3/N·m. The homogeneity of the superalloy Inconel 718 was also explored.

scholarly journals 3D Multi-Track and Multi-Layer Epitaxy Grain Growth Simulations of Selective Laser Melting

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7346
Author(s):  
Amir Reza Ansari Dezfoli ◽  
Yu-Lung Lo ◽  
M. Mohsin Raza
Keyword(s):  
Cooling Rate ◽  
Grain Growth ◽  
Selective Laser Melting ◽  
Laser Scanning ◽  
Processing Parameters ◽  
Grain Structure ◽  
Laser Melting ◽  
Scanning Strategy ◽  
Integrated Simulation ◽  
3D Finite Element Method

An integrated simulation framework consisting of the 3D finite element method and 3D cellular automaton method is presented for simulating the multi-track and multi-layer selective laser melting (SLM) process. The framework takes account of all the major multi-physics phenomena in the SLM process, including the initial grain structure, the growth kinetics, the laser scanning strategy, the laser–powder and laser–matter interactions, the melt flow, and the powder-to-liquid-to-solid transformations. The feasibility of the proposed framework is demonstrated by simulating the evolution of the epitaxy grain structure of Inconel 718 (IN718) during a 15-layer SLM process performed using a bi-directional 67° rotation scanning strategy and various SLM process parameters. The simulation results are found to be in good agreement with the experimental observations obtained in the present study and in the literature. In particular, a strong (001) texture is observed in the final component, which indicates that the grains with a preferred <001> orientation win the competitive epitaxy grain growth process. In addition, the size and shape of the IN718 grains are governed primarily by the cooling rate, where the cooling rate is determined in turn by the SLM parameters and the build height. Overall, the results show that the proposed framework provides an accurate approach for predicting the final microstructures of SLM components, and therefore, it can play an important role in optimizing the SLM processing parameters in such a way as to produce components with the desired mechanical properties.

Selective Laser Melting of Low-Modulus Biomedical Ti-24Nb-4Zr-8Sn Alloy: Effect of Laser Point Distance

2012 ◽  
Vol 520 ◽  
pp. 226-233 ◽  
Author(s):  
L.C. Zhang ◽  
T.B. Sercombe
Keyword(s):  
Selective Laser Melting ◽  
Laser Energy ◽  
Processing Parameters ◽  
Full Density ◽  
Laser Melting ◽  
Production Route ◽  
Incident Laser Energy ◽  
Alloy Effect ◽  
Low Modulus ◽  
Point Distance

As many complex processing parameters are involved in Selective Laser Melting (SLM), an understanding of the scientific and technical aspects of the production route on the microstructural evolution during SLM process is required in order to obtain parts with near full density and desirable surface finish. Although the effects of the various processing parameters on the density of parts have been well documented, the effect of laser point distance on density and mechanical properties of the SLM-produced parts has not been widely studied. In this paper, we present the results of using SLM to produce biomedical beta Ti-24Nb-4Zr-8Sn components. Both the density and hardness of the material increases with increasing incident laser energy and reaches a near full density value of >99% without any post-processing. When the laser energy density input is high enough to fully melt powder, the laser point distance has no influence on the density or hardness of the samples. In contrast, at low energy densities, large point distances have been shown to be detrimental.

Effect of defocusing distance on the forming quality of inner structure parts manufactured via selective laser melting

2021 ◽  
pp. 095440892110590
Author(s):  
Weipeng Duan ◽  
Meiping Wu ◽  
Jitai Han ◽  
Yiqing Ma ◽  
Peipei Lu ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Energy Density ◽  
Selective Laser Melting ◽  
Surface Pressure ◽  
Laser Energy ◽  
Dimensional Accuracy ◽  
Laser Energy Density ◽  
Laser Melting ◽  
Forming Quality

A systematical work was studied to illustrate the influence of defocusing distance on the forming quality of inner structure fabricated by selective laser melting for Ti-6Al-4V alloy. The relationship between defocusing distance and dimensional accuracy, surface roughness as well as flatness was investigated, finite element analysis (FEA) was used to show the temperature distribution. The results show that defocusing distance not only had an impact on laser energy density, but also showed a significant influence on the surface pressure of the metal powder. Smaller defocusing distance (0.0 mm) accompanied with higher molten pool maximum temperature (3262.96°C), powder melting and splashing at the same time. On the contrary, larger defocusing distance leading to unmelted powder and powder bonding, which influences the forming quality of samples. Dimensional accuracy was less affected in 0.0, 1.0, 2.0 mm defocusing distance (5%), but changed dramatically when it is 3.0 mm (22%). In the same condition, similar variation trend of surface roughness (Ra) and flatness was observed, and varying from 5.1 to 27.3 μm and 0.05 to 0.26 mm, respectively. Simultaneously, the bottom surface is less affected, while the other three sides have the opposite situation. Pores and unmelted powder can be seen on the surface, it is the comprehensive effect of laser energy density and surface pressure. It proves that it is feasible to manufacture inner structure by controlling this process parameter during SLM process, the influence mechanism of defocusing distance on forming quality was also illustrated in this work.

Effect of the strut size and tilt angle on the geometric characteristics of selective laser melting AlSi10Mg

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Baopeng Zhang ◽  
Xuesong Han ◽  
Changpeng Chen ◽  
Wenqi Zhang ◽  
Hailong Liao ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Compressive Strength ◽  
Selective Laser Melting ◽  
Process Parameters ◽  
Tilt Angle ◽  
Lattice Structure ◽  
Dimensional Accuracy ◽  
Optimal Process ◽  
Laser Melting ◽  
Content Type

Purpose The purpose of this study is to investigate the effect of the strut size and tilt angle on the densification behavior, surface roughness and dimensional accuracy of the selective laser melting AlSi10Mg lattice structure was investigated in this study. In this study, the characteristics such as the density, up-skin and down-skin roughness and dimensional accuracy of selective laser melting forming technology manufacturing (SLMed) AlSi10Mg cellular lattice structure were carried. This work reveals the effect of the strut size and tilt angle on the geometric characteristics of SLMed AlSi10Mg and is benefit for controlling the forming performance of the SLMed cellular lattice structure. Design/methodology/approach Based on AlSi10Mg powder, the influence of the tilt angle changed from 10° to 45° with an increment of 5° were investigated, the influence of the strut size was varied from 0.4 mm to 1.2 mm with an increment of 0.2 mm were investigated. The characteristics such as the density, up-skin and down-skin roughness, dimensional accuracy and mechanical properties of SLM-ed AlSi10Mg cellular lattice structure was carried. Findings Greater than 99% relative density can be achieved for different strut size when optimal process parameters are used. In the optimized process interval, the struts with a tilt angle of 10° can still be formed well, which is higher than the design limit of the inclined angle given in the related literature. The tilt angle has a significant effect on the surface roughness of the strut. The microhardness reached to 157 ± 3 HV, and the maximum compressive strength was 58.86 MPa, with the optimal process parameters. Originality/value In this study, the characteristics such as the density, up-skin and down-skin roughness and dimensional accuracy of SLMed AlSi10Mg cellular lattice structure were carried. With the optimal geometric parameters, the authors tested microhardness and compressive strength of the cellular lattice structure. The results of this study provide theoretical and experimental basis for the realization of high-quality manufacturing and optimization design of aluminum alloy cellular lattice structure, which will meet more diversified industrial needs.

scholarly journals Collaborative Optimization of Density and Surface Roughness of 316L Stainless Steel in Selective Laser Melting

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1601 ◽  
Author(s):  
Yong Deng ◽  
Zhongfa Mao ◽  
Nan Yang ◽  
Xiaodong Niu ◽  
Xiangdong Lu
Keyword(s):  
Surface Roughness ◽  
Stainless Steel ◽  
Relative Density ◽  
Selective Laser Melting ◽  
Laser Power ◽  
316L Stainless Steel ◽  
Scanning Speed ◽  
Processing Parameters ◽  
Collaborative Optimization ◽  
Laser Melting

Although the concept of additive manufacturing has been proposed for several decades, momentum in the area of selective laser melting (SLM) is finally starting to build. In SLM, density and surface roughness, as the important quality indexes of SLMed parts, are dependent on the processing parameters. However, there are few studies on their collaborative optimization during SLM to obtain high relative density and low surface roughness simultaneously in the literature. In this work, the response surface method was adopted to study the influences of different processing parameters (laser power, scanning speed and hatch space) on density and surface roughness of 316L stainless steel parts fabricated by SLM. A statistical relationship model between processing parameters and manufacturing quality is established. A multi-objective collaborative optimization strategy considering both density and surface roughness is proposed. The experimental results show that the main effects of processing parameters on the density and surface roughness are similar. We observed that the laser power and scanning speed significantly affected the above objective quality, but the influence of the hatch spacing was comparatively low. Based on the above optimization, 316L stainless steel parts with excellent surface roughness and relative density can be obtained by SLM with optimized processing parameters.

Selective Laser Melting of Mechanically Alloyed Metastable Al5Fe2 Powders

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Hugo Montiel ◽  
Ben Xu ◽  
Jianzhi Li
Keyword(s):  
Aluminum Alloys ◽  
Energy Density ◽  
Selective Laser Melting ◽  
Laser Power ◽  
Laser Scanning ◽  
Laser Energy ◽  
Scanning Speed ◽  
High Energy ◽  
Laser Energy Density ◽  
Laser Melting

Aluminum alloys, which are high-strength lightweight materials, were processed by selective laser melting (SLM) with high-energy consumption and poor finish due to quick heat dissipation. Previous investigations reported that SLM with 300 W laser power and 500 mm/s scanning speed can process the aluminum alloys, such as Al-Si12 and AlSi10Mg. This work aims to process the powders to alter their properties and to reduce the laser intensity required in the process, and it also reports that the SLM-processed Al–Fe alloys utilize the metastable alloy by mechanical alloying (MA). The elemental Al and Fe powders were first alloyed in a ball mill in a relative short time period (∼15 h) employing high milling intensities, high ball-to-powder ratio (≥20:1), and high milling velocities (≥400 rpm), which produced fine metastable Al–Fe powders, and these powders were processed later by the SLM. The optimum laser power, the scanning speed, hatch distance, and substrate temperature were investigated by a series of experiments. Experimental results indicated that decreasing the laser energy density while increasing the laser scanning speed can benefit for smoother laser hatch lines, and the metastable Al5Fe2 alloy powders can be processed and stabilized under a 200-W laser energy density and a scanning speed of 1000 mm/s. It is expected that the combination of pre-excited materials in a metastable phase will open a new window to optimize the SLM process for aluminum alloys and other metallic alloys.

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