Effect of Process Parameters on the Surface Microgeometry of a Ti6Al4V Alloy Manufactured by Laser Powder Bed Fusion: 3D vs. 2D Characterization

The influence of the main process parameters, laser power, point distance and time exposure, on the surface microgeometry of Ti6Al4V specimens produced by a pulsed powder bed fusion process was investigated. A 3D characterization was carried out and collected data were elaborated to reconstruct the surface and to determine both the 3D and the 2D material ratio curves along different directions. The 3D material ratio curve gives a slightly lower material ratio of peak zone Mr1 and higher material ratio of valley zone Mr2, reduced peak height Rpk and reduced valley height Rvk than the 2D curves. Roughness is greater in the 3D analysis than in the 2D one, skewness is the same and kurtosis increases from <3 in 2D to >3 in 3D. Roughness and skewness increase on increasing point distance and decreasing time exposure and laser power. Within the investigated ranges (27.3–71.2 J/mm3), an increase in energy density reduces the surface roughness while skewness and kurtosis are not significantly affected. The results indicate that a 3D approach allows better characterization of the surface microgeometry than a 2D one.

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Virtual Development of Process Parameters for Bulk Metallic Glass Formation in Laser-Based Powder Bed Fusion

Materials ◽

10.3390/ma15020450 ◽

2022 ◽

Vol 15 (2) ◽

pp. 450

Author(s):

Johan Lindwall ◽

Andreas Lundbäck ◽

Jithin James Marattukalam ◽

Anders Ericsson

Keyword(s):

Additive Manufacturing ◽

Metallic Glass ◽

Bulk Metallic Glass ◽

Process Parameters ◽

Glass Formation ◽

Laser Power ◽

Powder Bed Fusion ◽

Powder Bed ◽

Scanning Strategies ◽

Hatch Spacing

The development of process parameters and scanning strategies for bulk metallic glass formation during additive manufacturing is time-consuming and costly. It typically involves trials with varying settings and destructive testing to evaluate the final phase structure of the experimental samples. In this study, we present an alternative method by modelling to predict the influence of the process parameters on the crystalline phase evolution during laser-based powder bed fusion (PBF-LB). The methodology is demonstrated by performing simulations, varying the following parameters: laser power, hatch spacing and hatch length. The results are compared in terms of crystalline volume fraction, crystal number density and mean crystal radius after scanning five consecutive layers. The result from the simulation shows an identical trend for the predicted crystalline phase fraction compared to the experimental estimates. It is shown that a low laser power, large hatch spacing and long hatch lengths are beneficial for glass formation during PBF-LB. The absolute values show an offset though, over-predicted by the numerical model. The method can indicate favourable parameter settings and be a complementary tool in the development of scanning strategies and processing parameters for additive manufacturing of bulk metallic glass.

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Controlling the porosity of 316L stainless steel parts manufactured via the powder bed fusion process

Rapid Prototyping Journal ◽

10.1108/rpj-11-2017-0226 ◽

2019 ◽

Vol 25 (1) ◽

pp. 162-175 ◽

Cited By ~ 7

Author(s):

Abdullah AlFaify ◽

James Hughes ◽

Keith Ridgway

Keyword(s):

Stainless Steel ◽

Layer Thickness ◽

Exposure Time ◽

Process Parameters ◽

Pulsed Laser ◽

Powder Bed Fusion ◽

Content Type ◽

Powder Bed ◽

Point Distance ◽

Part Density

Purpose The pulsed-laser powder bed fusion (PBF) process is an additive manufacturing technology that uses a laser with pulsed beam to melt metal powder. In this case, stainless steel SS316L alloy is used to produce complex components. To produce components with acceptable mechanical performance requires a comprehensive understanding of process parameters and their interactions. This study aims to understand the influence of process parameters on reducing porosity and increasing part density. Design/methodology/approach The response surface method (RSM) is used to investigate the impact of changing critical parameters on the density of parts manufactured. Parameters considered include: point distance, exposure time, hatching distance and layer thickness. Part density was used to identify the most statistically significant parameters, before each parameter was analysed individually. Findings A clear correlation between the number and shape of pores and the process parameters was identified. Point distance, exposure time and layer thickness were found to significantly affect part density. The interaction between these parameters also critically affected the development of porosity. Finally, a regression model was developed and verified experimentally and used to accurately predict part density. Research limitations/implications The study considered a range of selected parameters relevant to the SS316L alloy. These parameters need to be modified for other alloys according to their physical properties. Originality/value This study is believed to be the first systematic attempt to use RSM for the design of experiments (DOE) to investigate the effect of process parameters of the pulsed-laser PBF process on the density of the SS316L alloy components.

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Influences of Process Parameters on the Microstructure and Mechanical Properties of CoCrFeNiTi Based High-Entropy Alloy in a Laser Powder Bed Fusion Process

Crystals ◽

10.3390/cryst11050549 ◽

2021 ◽

Vol 11 (5) ◽

pp. 549

Author(s):

Takafumi Ikeda ◽

Makiko Yonehara ◽

Toshi-Taka Ikeshoji ◽

Tohru Nobuki ◽

Minoru Hatate ◽

...

Keyword(s):

Mechanical Properties ◽

Surface Roughness ◽

Process Parameters ◽

Laser Power ◽

Powder Bed Fusion ◽

Process Map ◽

Powder Bed ◽

High Entropy ◽

Scan Speed ◽

Fabrication Condition

Recently, high-entropy alloys (HEAs) have attracted much attention because of their superior properties, such as high strength and corrosion resistance. This study aimed to investigate the influences of process parameters on the microstructure and mechanical properties of CoCrFe NiTiMo HEAs using a laser-based powder bed fusion (LPBF) process. In terms of laser power and scan speed, a process map was constructed by evaluating the density and surface roughness of the as-built specimen to optimize the process parameters of the products. The mechanical properties of the as-built specimens fabricated at the optimum fabrication condition derived from the process map were evaluated. Consequently, the optimum laser power and scan speed could be obtained using the process map evaluated by density and surface roughness. The as-built specimen fabricated at the optimum fabrication condition presented a relative density of more than 99.8%. The microstructure of the as-built specimen exhibited anisotropy along the build direction. The tensile strength and elongation of the as-built specimen were around 1150 MPa and more than 20%, respectively.

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Process Parameter Optimization in Metal Laser-Based Powder Bed Fusion Using Image Processing and Statistical Analyses

Metals ◽

10.3390/met12010087 ◽

2022 ◽

Vol 12 (1) ◽

pp. 87

Author(s):

Faiyaz Ahsan ◽

Jafar Razmi ◽

Leila Ladani

Keyword(s):

Contact Angle ◽

Process Parameters ◽

Laser Power ◽

Pool Size ◽

Scale Production ◽

Powder Bed Fusion ◽

Powder Bed ◽

Melt Pool ◽

Scan Speed ◽

Melt Pool Size

The powder bed fusion additive manufacturing process has received widespread interest because of its capability to manufacture components with a complicated design and better surface finish compared to other additive techniques. Process optimization to obtain high quality parts is still a concern, which is impeding the full-scale production of materials. Therefore, it is of paramount importance to identify the best combination of process parameters that produces parts with the least defects and best features. This work focuses on gaining useful information about several features of the bead area, such as contact angle, porosity, voids, melt pool size and keyhole that were achieved using several combinations of laser power and scan speed to produce single scan lines. These features are identified and quantified using process learning, which is then used to conduct a comprehensive statistical analysis that allows to estimate the effect of the process parameters, such as laser power and scan speed on the output features. Both single and multi-response analyses are applied to analyze the response parameters, such as contact angle, porosity and melt pool size individually as well as in a collective manner. Laser power has been observed to have a more influential effect on all the features. A multi-response analysis showed that 150 W of laser power and 200 mm/s produced a bead with the best possible features.

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Effect of Process Parameters and Layer Thickness on the Quality and Performance of Ti-6Al-4V Fabricated by Selective Laser Melting

Coatings ◽

10.3390/coatings11111323 ◽

2021 ◽

Vol 11 (11) ◽

pp. 1323

Author(s):

Yanlong Jing ◽

Peng Wang ◽

Xiaoling Yan

Keyword(s):

Surface Quality ◽

Selective Laser Melting ◽

Exposure Time ◽

Process Parameters ◽

Laser Power ◽

Single Track ◽

Laser Melting ◽

Powder Bed ◽

Point Distance

To improve the quality of thick powder bed and realize the matching of thick powder bed and thin powder bed in the later stage, the influence of process parameters for the single-track, multi-layer fabrication, relative density, surface quality, defect, remelting, and boundary optimization performance of different layer thicknesses of Ti-6Al-4V fabricated by selective laser melting were investigated. It is more conducive to the stable forming of single-track when the point distance is half the diameter of the laser beam, and the exposure time is appropriately extended. The thin powder bed needs the corresponding point distance and exposure time under the laser power of 280–380 W to obtain high-density specimens. The thick powder bed needs to be able to ensure the formation of high-quality specimens under the smaller point distance and longer exposure time under higher laser power of 380 W. Both thick powder bed and thin powder bed will cause un-melted defects between molten pools, spheroidization defects caused by splashing, and microporous defects. The remelting process can significantly improve the surface quality of the formed specimen, but the surface quality of the thick powder bed is worse than that of the thin powder bed. The boundary quality of thick powder bed is worse than that of thin powder bed, and the boundary shape has a greater influence on the quality of the SLM forming boundary. Different strategies should be adopted to form the boundary of different shapes. Increasing the boundary count and increasing the laser power are more conducive to the improvement of boundary quality.

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On the Relevance of Volumetric Energy Density in the Investigation of Inconel 718 Laser Powder Bed Fusion

Materials ◽

10.3390/ma13030538 ◽

2020 ◽

Vol 13 (3) ◽

pp. 538 ◽

Cited By ~ 6

Author(s):

Fabrizia Caiazzo ◽

Vittorio Alfieri ◽

Giuseppe Casalino

Keyword(s):

Surface Roughness ◽

Energy Density ◽

Process Parameters ◽

Vickers Hardness ◽

Powder Bed Fusion ◽

Processing Conditions ◽

Laser Powder Bed Fusion ◽

Powder Bed ◽

Fractional Density ◽

Experimental Variation

Laser powder bed fusion (LPBF) can fabricate products with tailored mechanical and surface properties. In fact, surface texture, roughness, pore size, the resulting fractional density, and microhardness highly depend on the processing conditions, which are very difficult to deal with. Therefore, this paper aims at investigating the relevance of the volumetric energy density (VED) that is a concise index of some governing factors with a potential operational use. This paper proves the fact that the observed experimental variation in the surface roughness, number and size of pores, the fractional density, and Vickers hardness can be explained in terms of VED that can help the investigator in dealing with several process parameters at once.

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Comparison of Phase Characteristics and Residual Stresses in Ti-6Al-4V Alloy Manufactured by Laser Powder Bed Fusion (L-PBF) and Electron Beam Powder Bed Fusion (EB-PBF) Techniques

Crystals ◽

10.3390/cryst11070796 ◽

2021 ◽

Vol 11 (7) ◽

pp. 796

Author(s):

Aya Takase ◽

Takuya Ishimoto ◽

Naotaka Morita ◽

Naoko Ikeo ◽

Takayoshi Nakano

Keyword(s):

Electron Beam ◽

Residual Stresses ◽

Cooling Rate ◽

Process Parameters ◽

Phase Evolution ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Solidification Temperature ◽

Powder Bed ◽

Β Phase

Ti-6Al-4V alloy fabricated by laser powder bed fusion (L-PBF) and electron beam powder bed fusion (EB-PBF) techniques have been studied for applications ranging from medicine to aviation. The fabrication technique is often selected based on the part size and fabrication speed, while less attention is paid to the differences in the physicochemical properties. Especially, the relationship between the evolution of α, α’, and β phases in as-grown parts and the fabrication techniques is unclear. This work systematically and quantitatively investigates how L-PBF and EB-PBF and their process parameters affect the phase evolution of Ti-6Al-4V and residual stresses in the final parts. This is the first report demonstrating the correlations among measured parameters, indicating the lattice strain reduces, and c/a increases, shifting from an α’ to α+β or α structure as the crystallite size of the α or α’ phase increases. The experimental results combined with heat-transfer simulation indicate the cooling rate near the β transus temperature dictates the resulting phase characteristics, whereas the residual stress depends on the cooling rate immediately below the solidification temperature. This study provides new insights into the previously unknown differences in the α, α’, and β phase evolution between L-PBF and EB-PBF and their process parameters.

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Role of laser powder bed fusion process parameters in crystallographic texture of additive manufactured Nb-48Ti alloy

Journal of Materials Research and Technology ◽

10.1016/j.jmrt.2021.06.054 ◽

2021 ◽

Author(s):

Rafael de Moura Nobre ◽

Willy Ank de Morais ◽

Matheus Tavares Vasques ◽

Jhoan Guzmán ◽

Daniel Luiz Rodrigues Junior ◽

...

Keyword(s):

Process Parameters ◽

Crystallographic Texture ◽

Fusion Process ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Powder Bed

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Optimizing Laser Powder Bed Fusion Parameters for IN-738LC by Response Surface Method

Materials ◽

10.3390/ma13214879 ◽

2020 ◽

Vol 13 (21) ◽

pp. 4879

Author(s):

Mireia Vilanova ◽

Rubén Escribano-García ◽

Teresa Guraya ◽

Maria San Sebastian

Keyword(s):

Response Surface ◽

Response Surface Method ◽

Process Parameters ◽

Crack Density ◽

Processing Parameters ◽

Optimum Process ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Powder Bed ◽

Surface Method

A method to find the optimum process parameters for manufacturing nickel-based superalloy Inconel 738LC by laser powder bed fusion (LPBF) technology is presented. This material is known to form cracks during its processing by LPBF technology; thus, process parameters have to be optimized to get a high quality product. In this work, the objective of the optimization was to obtain samples with fewer pores and cracks. A design of experiments (DoE) technique was implemented to define the reduced set of samples. Each sample was manufactured by LPBF with a specific combination of laser power, laser scan speed, hatch distance and scan strategy parameters. Using the porosity and crack density results obtained from the DoE samples, quadratic models were fitted, which allowed identifying the optimal working point by applying the response surface method (RSM). Finally, five samples with the predicted optimal processing parameters were fabricated. The examination of these samples showed that it was possible to manufacture IN738LC samples free of cracks and with a porosity percentage below 0.1%. Therefore, it was demonstrated that RSM is suitable for obtaining optimum process parameters for IN738LC alloy manufacturing by LPBF technology.

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