Effect of processing parameters on forming defects during selective laser melting of AlSi10Mg powder

2020 ◽  
Vol 26 (5) ◽  
pp. 871-879 ◽  
Author(s):  
Haihua Wu ◽  
Junfeng Li ◽  
Zhengying Wei ◽  
Pei Wei
Keyword(s):  
Selective Laser Melting ◽  
Laser Power ◽  
Scanning Speed ◽  
Processing Parameters ◽  
Argon Pressure ◽  
Powder Layer ◽  
Laser Melting ◽  
Content Type ◽  
Scan Speed ◽  
Forming Defects

Purpose To fabricate a selective laser melting (SLM)-processed AlSi10Mg part with almost full density and free of any apparent pores, this study aims to investigate the effect of ambient argon pressure and laser scanning speed on the particles splash during the AlSi10Mg powder bed laser melting. Design/methodology/approach Based on the discrete element method (DEM), a 3D model of random distribution of powder particles was established, and the 3D free surface of SLM forming process was dynamically tracked by the volume of fluid, where a Gaussian laser beam acts as the energy source melting the powder bed. Through the numerical simulation and process experimental research, the effect of the applied laser power and scanning speed on the operating laser melting temperature was studied. Findings The process stability has a fundamental role in the porosity formation, which is process-dependent. The effect of the processing conditions on the process stability and the resultant forming defects were clarified. Research limitations/implications The results shows that the pores were the main defects present in the SLM-processed AlSi10Mg sample, which decreases the densification level of the sample. Practical implications The optimal processing parameters (argon pressure of 1,000 Pa, laser power of 180 W, scan speed of 1,000 mm/s, powder layer thickness of 35 µm and hatch spacing of 50 µm ) applied during laser melting can improve the quality of selective laser melting of AlSi10Mg, Social implications It can provide a technological support for 3D printing. Originality/value Based on the analysis of the pore and balling formation mechanisms, the optimal processing parameters have been obtained, which were argon pressure of 1,000 Pa, laser power of 180 W, scan speed of 1,000 mm/s, powder layer thickness of 35 µm and hatch spacing of 50 µm. Then, a near-fully dense sample free of any apparent pores on the cross-sectional microstructure was produced by SLM, wherein the relative density of the as-built samples is larger than 97.5%.

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”.

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 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 Optimisation of selective laser melting for a high temperature Ni-superalloy

2015 ◽  
Vol 21 (4) ◽  
pp. 423-432 ◽  
Author(s):  
Luke N. Carter ◽  
Khamis Essa ◽  
Moataz M Attallah
Keyword(s):  
High Temperature ◽  
Response Surface ◽  
Selective Laser Melting ◽  
Process Parameters ◽  
Laser Power ◽  
Surface Model ◽  
Good Prediction ◽  
Laser Melting ◽  
Content Type ◽  
Scan Speed

Purpose – The purpose of this paper is to optimise the selective laser melting (SLM) process parameters for CMSX486 to produce a “void free” (fully consolidated) material, whilst reducing the cracking density to a minimum providing the best possible fabricated material for further post-processing. SLM of high temperature nickel base superalloys has had limited success due to the susceptibly of the material to solidification and reheat cracking. Design/methodology/approach – Samples of CMSX486 were fabricated by SLM. Statistical design of experiments (DOE) using the response surface method was used to generate an experimental design and investigate the influence of the key process parameters (laser power, scan speed, scan spacing and island size). A stereological technique was used to quantify the internal defects within the material, providing two measured responses: cracking density and void per cent. Findings – The analysis of variance (ANOVA) was used to determine the most significant process parameters and showed that laser power, scan speed and the interaction between the two are significant parameters when considering the cracking density. Laser power, scan speed, scan spacing and the interaction between power and speed, and speed and spacing were the significant factors when considering void per cent. The optimum setting of the process parameters that lead to minimum cracking density and void per cent was obtained. It was shown that the nominal energy density can be used to identify a threshold for the elimination of large voids; however, it does not correlate well to the formation of cracks within the material. To validate the statistical approach, samples were produced using the predicted optimum parameters in an attempt to validate the response surface model. The model showed good prediction of the void per cent; however, the cracking results showed a greater deviation from the predicted value. Originality/value – This is the first ever study on SLM of CMSX486. The paper shows that provided that the process parameters are optimised, SLM has the potential to provide a low-cost route for the small batch production of high temperature aerospace components.

Geometrical feature analysis of Co-Cr-Mo single tracks after selective laser melting processing

2015 ◽  
Vol 21 (3) ◽  
pp. 287-300 ◽  
Author(s):  
Karla Monroy ◽  
Jordi Delgado ◽  
Lidia Sereno ◽  
Joaquim Ciurana ◽  
Nicolas J Hendrichs
Keyword(s):  
Selective Laser Melting ◽  
Scanning Speed ◽  
Processing Parameters ◽  
Single Track ◽  
Cobalt Chromium ◽  
Laser Melting ◽  
Content Type ◽  
Dimensional Precision ◽  
Morphologic Characteristics ◽  
Definition Of

Purpose – Therefore, the purpose of this study is to understand the relationships between the processing parameters and the geometric form of the produced single tracks, in order to control dimensional quality in future experimentations. The quality of the deposited single track and layer is of prime importance in the selective laser melting (SLM) process, as it affects the product quality in terms of dimensional precision and product performance. Design/methodology/approach – In this paper, a vertical milling machining center equipped with an Ytterbium-fiber laser was used in the SLM experimentation to form single cobalt-chromium-molybdenum (CoCrMo) tracks. The different geometric features and the influence of the scanning parameters on these morphologic characteristics were studied statistically by means of ANOVA. Findings – Evidently, track height (h1) inaccuracy reduced in layer thicknesses between 100 and 200 μm. The re-melt depth (h2) was determined by the energy parameters, with laser power of 325-350 W and scanning speed (SS) of 66.6-83.3 mm/s being the most favorable parameters to obtain the required anchoring. Moreover, a contact angle of 117° was proposed as optimal, as it permitted an adequate overlapping region and a full densification, and, finally, an SS of 50 mm/s and a layer thickness of 250 were suggested for its development. Originality/value – The comprehension of the phenomena inherent to the process is related to the single track geometrical characteristics, which allow the definition of an optimal value for each factor for a further proposal of processing conditions that can finally derive a higher precision, wetting, density and mechanical properties.

Densification behavior of 316L-NiB stainless steel powder and surface morphology during selective laser melting process using pulsed Nd:YAG laser

2019 ◽  
Vol 25 (1) ◽  
pp. 47-54 ◽  
Author(s):  
Jelena Stašić ◽  
Dušan Božić
Keyword(s):  
Stainless Steel ◽  
Layer Thickness ◽  
Selective Laser Melting ◽  
Laser Power ◽  
Average Power ◽  
Favorable Effect ◽  
Powder Layer ◽  
Laser Melting ◽  
Content Type ◽  
Hcl Solution

Purpose This paper aims to report the production of 316L-1 Wt.% NiB cubes by using the selective laser melting (SLM) process. The laser used was pulsed, millisecond Nd:YAG system with maximum average power 100 W. Design/methodology/approach Densification under different processing conditions (pulse energy, average laser power, laser scan speed, powder layer thickness, pulse frequency) was investigated. Morphology, macro and microstructure of laser melted samples were characterized by digital camera images and by scanning electron microscope. Density of the cubes was determined by Archimedes method in water. Vickers microhardness of samples was determined under the load of 25 g. Corrosion behavior of 316L and 316L-NiB samples was conducted in 5 per cent HCl solution at the testing temperature of 20°C during 240 h. Findings Using laser power of ∼60-70 W, lower beam overlap and powder layer thickness of 200 µm, 3D cubical samples were obtained with significant balling in individual layers and an overall porosity being around 30 per cent. By increasing laser power to ∼80 W, with higher beam overlap and lower powder layer thickness of 100 µm, SLM parts with no balling and the presence of small pores of up to 4 per cent (20 Hz) and 9 per cent (40 Hz) were obtained. With further increase of laser power to 90 W, overall porosity rose to around 12 per cent. The addition of 1 Wt.% NiB to stainless steel negligibly lowered its corrosion resistance in 5 per cent HCl solution. Originality/value A part from 316L stainless steel with balling-free structure and good density was successfully obtained through pulsed-SLM process with the aid of 1 Wt.% of NiB addition. Aside from significant influence on the improved structure of cubes, NiB had a favorable effect on microhardness values while practically not affecting the corrosion resistivity of the base material in an aggressive surrounding.

Influence of laser parameters on the surface morphology of slurry-based Al2O3 parts produced through selective laser melting

2018 ◽  
Vol 24 (2) ◽  
pp. 333-341 ◽  
Author(s):  
Kai Zhang ◽  
Tingting Liu ◽  
Wenhe Liao ◽  
Changdong Zhang ◽  
Yishuai Yan ◽  
...  
Keyword(s):  
Surface Morphology ◽  
Surface Quality ◽  
Selective Laser Melting ◽  
Laser Power ◽  
High Performance ◽  
Thermocapillary Convection ◽  
Scanning Speed ◽  
Laser Melting ◽  
Content Type ◽  
Laser Parameters

Purpose The purpose of this paper is to obtain high-performance ceramics and enrich additive manufacturing of ceramic parts. Also, a new manufacturing technique based on slurry by selective laser melting (SLM) was studied, which has some significant advantages compared to indirect selective laser sintering of ceramic powders. Design/methodology/approach To study the effect of laser parameters on the surface morphology and melting state of pure Al2O3 ceramics, laser power varied between 100 and 200 W and scan speed varied between 60 and 90 mm/s. Findings Experimental results show that Al2O3 slurry melts completely when the laser power is about 200 W and the scanning speed is 90 mm/s. Surface quality cannot be improved effectively by changing the scanning speed. However, surface quality improves when the laser power is 200∼205 W and energy density is 889∼911 J/mm3. Thermocapillary convection was observed during SLM. By changing the temperature gradient, streak convection and flowing Bénard cells were obtained during SLM of Al2O3 slurry. Originality/value It is feasible to produce slurry ceramic parts without binders through SLM. Increasing the laser power is the most effective way to fully melt the ceramics. Complex thermocapillary convection was observed during this new process; it may be used to produce crystals.

scholarly journals The Effects of Selective Laser Melting Process Parameters on Relative Density of the AlSi10Mg Parts and Suitable Procedures of the Archimedes Method

2019 ◽  
Vol 9 (3) ◽  
pp. 583 ◽  
Author(s):  
Shigang Bai ◽  
Nataliya Perevoshchikova ◽  
Yu Sha ◽  
Xinhua Wu
Keyword(s):  
Image Analysis ◽  
Relative Density ◽  
Selective Laser Melting ◽  
Laser Power ◽  
Regression Models ◽  
Processing Parameters ◽  
Response Surfaces ◽  
Laser Melting ◽  
High Relative Density ◽  
Scan Speed

In view of the importance of accurately measuring the relative density of a selective laser melted (SLMed) part for optimizing the selective laser melting (SLM) processing parameters, suitable procedures of the Archimedes method considering the surface-connected cavities were proposed by comparing the results using the Archimedes method with image analysis. The effects of the SLM processing parameters on the relative density of AlSi10Mg were investigated using the proposed procedures of the Archimedes methods and image analysis. Fourteen SLMed samples were produced by different SLM processing parameters according to Doehlert Matrix. The regression models correlating relative density and three SLM processing parameters (laser power, scan speed, and hatching distance) were built and the optimum parameter combination to get a high relative density was obtained. By plotting the response surfaces and contours of the regression models, it was found that the relative densities are both higher at the combination of the higher scan speed, higher power, and lower hatching distance and at the combination of a lower scan speed, a moderate laser power, and a optional hatching distance. It was also found that the parameter of hatching distance is the crucial parameter to get a high relative density and to get high mechanical property.

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.

Optimization of built-part distortion in laser powder bed fusion processing of Inconel 718

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
You-Cheng Chang ◽  
Hong-Chuong Tran ◽  
Yu-Lung Lo
Keyword(s):  
Cooling Rate ◽  
Cantilever Beam ◽  
Laser Power ◽  
Scanning Speed ◽  
Processing Parameters ◽  
Laser Powder Bed Fusion ◽  
Simulation Framework ◽  
Content Type ◽  
Powder Bed ◽  
Simulation Results

Purpose Laser powder bed fusion (LPBF) provides the means to produce unique components with almost no restriction on geometry in an extremely short time. However, the high-temperature gradient and high cooling rate produced during the fabrication process result in residual stress, which may prompt part warpage, cracks or even baseplate separation. Accordingly, an appropriate selection of the LPBF processing parameters is essential to ensure the quality of the built part. This study, thus, aims to develop an integrated simulation framework consisting of a single-track heat transfer model and a modified inherent shrinkage method model for predicting the curvature of an Inconel 718 cantilever beam produced using the LPBF process. Design/methodology/approach The simulation results for the curvature of the cantilever beam are calibrated via a comparison with the experimental observations. It is shown that the calibration factor required to drive the simulation results toward the experimental measurements has the same value for all settings of the laser power and scanning speed. Representative combinations of the laser power and scanning speed are, thus, chosen using the circle packing design method and supplied as inputs to the validated simulation framework to predict the corresponding cantilever beam curvature and density. The simulation results are then used to train artificial neural network models to predict the curvature and solid cooling rate of the cantilever beam for any combination of the laser power and scanning speed within the input design space. The resulting processing maps are screened in accordance with three quality criteria, namely, the part density, the radius of curvature and the solid cooling rate, to determine the optimal processing parameters for the LPBF process. Findings It is shown that the parameters lying within the optimal region of the processing map reduce the curvature of the cantilever beam by 17.9% and improve the density by as much as 99.97%. Originality/value The present study proposes a computational framework, which could find the parameters that not only yield the lowest distortion but also produce fully dense components in the LPBF process.

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