scholarly journals Investigation of Laser Polishing of Four Selective Laser Melting Alloy Samples

2020 ◽  
Vol 10 (3) ◽  
pp. 760
Author(s):  
Dongqi Zhang ◽  
Jie Yu ◽  
Hui Li ◽  
Xin Zhou ◽  
Changhui Song ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Selective Laser Melting ◽  
Laser Power ◽  
Layer By Layer ◽  
Metal Powders ◽  
Laser Melting ◽  
Laser Polishing

Selective laser melting (SLM) is a layer by layer process of melting and solidifying of metal powders. The surface quality of the previous layer directly affects the uniformity of the next layer. If the surface roughness value of the previous layer is large, there is the possibility of not being able to complete the layering process such that the entire process has to be abandoned. At least, it may result in long term durability problem and the inhomogeneity, may even make the processed structure not be able to be predicted. In the present study, the ability of a fiber laser to in-situ polish the rough surfaces of four typical additive-manufactured alloys, namely, Ti6Al4V, AlSi10Mg, 316L and IN718 was demonstrated. The results revealed that the surface roughness of the as-received alloys could be reduced to about 3 μm through the application of the laser-polishing process, and the initial surfaces had roughness values of 8.80–16.64 μm. Meanwhile, for a given energy density, a higher laser power produced a laser-polishing effect that was often more obvious, with the surface roughness decreasing with an increase in the laser power. Further, the polishing strategy will be optimized by simulation in our following study.

scholarly journals Experiment of Process Strategy of Selective Laser Melting Forming Metal Nonhorizontal Overhanging Structure

Metals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 385 ◽  
Author(s):  
Wentian Shi ◽  
Peng Wang ◽  
Yude Liu ◽  
Guoliang Han
Keyword(s):  
Surface Roughness ◽  
Selective Laser Melting ◽  
Laser Power ◽  
316L Stainless Steel ◽  
Laser Melting ◽  
Scanning Strategy ◽  
Forming Quality ◽  
Forming Angle ◽  
Suspension Structure

To improve the precision of the nonhorizontal suspension structure and the forming quality of the overhanging surface by selective laser melting, the influence of laser power on the upper surface and the overhanging surface forming quality of 316L stainless steel at different forming angles was studied in the experiment. The influence of different scanning strategies, upper surface remelting optimization, and overhang boundary scanning optimization on the formation of overhanging structures was compared and analyzed. The forming effect of chromium–nickel alloy is better than 316L stainless steel below the limit forming angle in the overhanging structure. The better forming effect of chromium–nickel alloy can be obtained by narrowing the hatch space with the boundary optimization process. The experiment results show that the forming of the overhanging structure below the limit forming angle should adopt the chessboard scanning strategy. The smaller laser power remelting is beneficial to both the forming of the overhanging surface and the quality of upper surface forming. The minimum value of surface roughness using the 110 W power laser twice during surface remelting and boundary scanning 75° overhanging surface can reach 11.9 μm and 31.1μm, respectively. The forming accuracy error range above the limit forming angle is controlled within 0.4 mm, and the forming quality is better. A boundary count scanning strategy was applied to this study to obtain lower overhanging surface roughness values. This research proposes a process optimization and improvement method for the nonhorizontal suspension structure formed by selective laser melting, which provides the process support for practical application.

Modeling, Simulation and Experimental Validation of Heat Transfer During Selective Laser Melting

2015 ◽  
Author(s):  
Mohammad Masoomi ◽  
Xiang Gao ◽  
Scott M. Thompson ◽  
Nima Shamsaei ◽  
Linkan Bian ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mechanical Properties ◽  
Selective Laser Melting ◽  
Heat Fluxes ◽  
Transient Temperature ◽  
Thermal Gradients ◽  
Layer By Layer ◽  
Metal Powders ◽  
Laser Melting ◽  
Powder Bed

Selective Laser Melting (SLM), a laser powder-bed fusion (PBF-L) additive manufacturing method, utilizes a laser to selectively fuse adjacent metal powders. The powders are aligned in a bed that moves vertically to allow for layer-by-layer part construction-Process-related heat transfer and thermal gradients have a strong influence on the microstructural features, and subsequent mechanical properties, of the parts fabricated via SLM. In order to understand and control the heat transfer inherent to SLM, and to ensure high quality parts with targeted microstructures and mechanical properties, comprehensive knowledge of the related energy and mass transport during manufacturing is required. In this study, the transient temperature distribution within and around parts being fabricated via SLM is numerically simulated and the results are provided to aid in quantify the SLM heat transfer. In order to verify simulation output, and to estimate actual thermal gradients and heat transfer, experiments were separately conducted within a SLM machine using a substrate with embedded thermocouples. The experiments focused on characterizing heat fluxes during initial deposition on an initially-cold substrate and during the fabrication of a thin-walled structure built via stainless steel 17-4 powders. Results indicate that it is important to model heat transfer thorough powder bed as well as substrate.

scholarly journals Interferometry of Gas-Phase Flows during Selective Laser Melting

2019 ◽  
Vol 10 (1) ◽  
pp. 231 ◽  
Author(s):  
Pavel A. Podrabinnik ◽  
Alexander E. Shtanko ◽  
Roman S. Khmyrov ◽  
Andrey D. Korotkov ◽  
Andrey V. Gusarov
Keyword(s):  
Gas Phase ◽  
Selective Laser Melting ◽  
Laser Power ◽  
Metal Vapor ◽  
Gas Jet ◽  
Laser Melting ◽  
Pressure Fields ◽  
Ambient Gas ◽  
Processing Zone

Gas-phase flows occurring in a plume in a processing zone during selective laser melting (SLM) can significantly affect the quality of the process. To further enhance SLM performance, the characteristics of the flows should be considered. In this article, the vapor-gas jet emerging from the laser processing zone was studied. It was visualized by interferometry to evaluate flow velocity, geometry and changes in refractory index depending on laser power. The velocity and pressure fields of the vapor jet and the entrained ambient gas were estimated by mathematical modeling. It was shown that the increase of laser power led to higher jet velocity and greater change in its refractory index. The latter also was used to evaluate the content of metal vapor in the plume and its influence on the absorption of laser radiation.

scholarly journals Laser Polishing of Ti6Al4V Fabricated by Selective Laser Melting

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 191 ◽  
Author(s):  
Chunyong Liang ◽  
Yazhou Hu ◽  
Ning Liu ◽  
Xianrui Zou ◽  
Hongshui Wang ◽  
...  
Keyword(s):  
Selective Laser Melting ◽  
Surface Defects ◽  
Fatigue Behavior ◽  
Osteoblastic Differentiation ◽  
Laser Melting ◽  
Laser Polishing ◽  
Laser Process ◽  
High Roughness ◽  
Dental Applications

Selective laser melting (SLM) is emerging as a promising 3D printing method for orthopedic and dental applications. However, SLM-based Ti6Al4V components frequently exhibit high roughness values and partial surface defects. Laser polishing (LP) is a newly developed technology to improve the surface quality of metals. In this research, LP is applied to improve the surface finish of components. The results show that the laser beam can neatly ablate the aggregates of metallic globules and repair cracks and pores on the surface, resulting in a smooth surface with nanocomposites. Overall, the results indicate that using LP optimizes surface morphology to favor fatigue behavior and osteoblastic differentiation. These findings provide foundational data to improve the surface roughness of a laser-polished implant and pave the way for optimized mechanical behavior and biocompatibility via the laser process.

Experimental Investigation of Selective Laser Melting of Lunar Regolith for In-Situ Applications

2013 ◽  
Author(s):  
Miranda Fateri ◽  
Andreas Gebhardt ◽  
Maziar Khosravi
Keyword(s):  
Selective Laser Melting ◽  
Laser Power ◽  
Lunar Regolith ◽  
Laser Melting ◽  
Manufacturing Method ◽  
3D Objects ◽  
Scan Speed ◽  
Manufacturing Methods ◽  
Object Layer

Selective Laser Melting (SLM) is a powder based Additive manufacturing (AM) technology which builds an object layer wise using a laser beam to melt the powder on an elevated platform. Thus far numerous studies have investigated lunar manufacturing methods and construction but little is known about applicability of SLM of lunar regolith. As most lunar construction proposals require transportation of essential materials from Earth, using an in-situ manufacturing method with indigenous material would be considerably more economical. Fabrication of parts with SLM using various metals and ceramics has already been presented. As such, the feasibility of using lunar regolith mixture to create functional parts with SLM process is investigated. Variation of process parameters such as laser power, scan speed, and scan strategies is investigated and multiple 3D objects are successfully created and presented.

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.

scholarly journals In Situ Mo(Si,Al)2-Based Composite through Selective Laser Melting of a MoSi2-30 wt.% AlSi10Mg Mixture

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3720 ◽  
Author(s):  
Tatevik Minasyan ◽  
Sofiya Aydinyan ◽  
Ehsan Toyserkani ◽  
Irina Hussainova
Keyword(s):  
High Temperature ◽  
Selective Laser Melting ◽  
Laser Power ◽  
Laser Scanning ◽  
Scanning Speed ◽  
Laser Melting ◽  
Structural Applications ◽  
Laser Scanning Speed ◽  
Fusion Approach

The laser power bed fusion approach has been successfully employed to manufacture Mo(Si,Al)2-based composites through the selective laser melting of a MoSi2-30 wt.% AlSi10Mg mixture for high-temperature structural applications. Composites were manufactured by leveraging the in situ reaction of the components during printing at 150–300 W laser power, 500–1000 mm·s−1 laser scanning speed, and 100–134 J·mm−3 volumetric energy density. Microcomputed tomography scans indicated a negligible induced porosity throughout the specimens. The fully dense Mo(Si1-x,Alx)2-based composites, with hardness exceeding 545 HV1 and low roughness for both the top (horizontal) and side (vertical) surfaces, demonstrated that laser-based additive manufacturing can be exploited to create unique structures containing hexagonal Mo(Si0.67Al0.33)2.

Effects of the Processing Parameters on the Forming Quality of Stainless Steel Parts by Selective Laser Melting

2011 ◽  
Vol 189-193 ◽  
pp. 3668-3671 ◽  
Author(s):  
Qing Song Wei ◽  
Xiao Zhao ◽  
Li Wang ◽  
Rui Di Li ◽  
Jie Liu ◽  
...  
Keyword(s):  
Layer Thickness ◽  
Selective Laser Melting ◽  
Molten Pool ◽  
Laser Power ◽  
Single Layer ◽  
Scanning Speed ◽  
Processing Parameters ◽  
Powder Layer ◽  
Laser Melting

Selective Laser Melting (SLM) can produce high-performance metal parts with complex structures. However, it’s difficult to control the processing parameters, because many factors involves. From the perspective of the molten pool, the study focuses on the effects of processing parameters, including scanning speed, laser power, scanning space, layer thickness, and scanning strategies, on the surface quality, the balling effect, the density of SLM parts, by conducting experiments of single track, single layer and block forming. The results show that the quality of the molten pool is affected by laser power and scanning speed. Scanning drove in the strategy of “jumping and turning”，a smooth surface and a less balling effect will be obtained. The thicker the powder layer is, the lower density will be obtained. The optimal parameters from series of experiments are: laser power of 98W; scanning speed of 90mm/s; scanning space of 0.07mm; layer thickness of 0.1mm; and scanning strategy of “jumping and turning”.

A Study on Effect of Different Process Parameters on the Quality of Overhang Surface Produced by Selective Laser Melting

2018 ◽  
Author(s):  
Sagar Sarkar ◽  
Ankit Porwal ◽  
Nuthalapati Yaswanth ◽  
Ashish Kumar Nath
Keyword(s):  
Aspect Ratio ◽  
Selective Laser Melting ◽  
Process Parameters ◽  
Support Structures ◽  
Metal Powders ◽  
Laser Melting ◽  
Scanning Strategy ◽  
Support Structure ◽  
Laser Process

Selective Laser Melting process enables production of geometrically complex parts directly from CAD model by melting metal powders layer by layer. For successful building of parts, some auxiliary structures namely support structures are also built to ensure proper heat conduction from actual parts to be built to the base plate. Support structures are needed if there are overhang surfaces in the design of the part. If the design of the part is very complex and features many overhang surfaces, then too many supports get generated. After building the part, these support structures need to be removed properly to get desired geometrical features and it may deteriorate the surface quality from where supports are removed. Sometimes removal of support structures becomes very difficult specially for parts having internal features. In this study, first effect of inclined angle, aspect ratio and different scanning strategies on the quality of overhang surfaces produced without any support structure under constant laser power and scan speed has been investigated. Scanning Electron Microscopy (SEM) images of overhang surfaces have been analyzed to investigate the presence of warping and uneven fused edges if any. It was found that with increase in inclined angles and aspect ratio, warping and presence of uneven fused edges increases. Rotational scanning strategy found to be better than linear alternate scanning strategy for reduced uneven fused edges formation and warping. Results show an overhang without any support structure can be built successfully with a single laser process parameters upto 25.343 degree which is less than theoretical critical angle of 26.565 degree. Further, it has been shown, using a novel strategy of building overhang with multiple laser process parameters, it is possible to build overhang even upto 24.132 degree.

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.

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