Predicting the porosity defects in selective laser melting (SLM) by molten pool geometry

Liu, Binqi; Fang, Gang; Lei, Liping; Yan, Xingchen

doi:10.1016/j.ijmecsci.2022.107478

Cited by 53 publications

(7 citation statements)

References 34 publications

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“…The lack of fusion porosity was formed during the conduction while laser melting where the laser input energy is less and fails to fully melt the powder layer. However, when the input energy density is high, then a collapse of keyhole pores is formed (Liu et al , 2022). The schematic of user interface with simulation parameters and process physics details can be seen in Figure 8(a) and (b), simulation details in Table 3 and results of simulations are reported in Table 4 and Figure 9.…”

Section: Resultsmentioning

confidence: 99%

Manufacturability study in laser powder bed fusion of biomedical Ti alloys for orthopedic implants: an investigation of mechanical properties, process-induced porosity and surface roughness

Rehman

Wang

Ishfaq

et al. 2023

RPJ

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Purpose Since the biomedical implants with an improved compressive strength, near bone elastic modulus, controlled porosity, and sufficient surface roughness, can assist in long term implantation. Therefore, the fine process tuning plays its crucial role to develop optimal settings to achieve these desired properties. This paper aims to find applications for fine process tuning in laser powder bed fusion of biomedical Ti alloys for load-bearing implants. Design/methodology/approach In this work, the parametric porosity simulations were initially performed to simulate the process-induced porosity for selective laser-melted Ti6Al4V as per full factorial design. Continually, the experiments were performed to validate the simulation results and perform multiresponse optimization to fine-tune the processing parameters. Three levels of each control variable, namely, laser power – Pl (180, 190, 200) W, scanning speed – Vs (1500, 1600, 1700) mm/s and scan orientation – ϴ{1(0,0), 2(0,67°), 3(0,90°)} were used to investigate the processing performance. The measured properties from this study include compressive yield strength, elastic modulus, process-induced porosity and surface roughness. Finally, confirmatory experiments and comparisons with the already published works were also performed to validate the research results. Findings The results of porosity parametric simulation and experiments in selective laser melting of Ti6Al4V were found close to each other with overall porosity (less than 10%). The fine process tuning was resulted in optimal settings [Pl (200 W), Vs (1500 mm/s), ϴ (0,90°)], [Pl (200 W), Vs (1500 mm/s), ϴ (0,67°)], [Pl (200 W), Vs (1500 mm/s), ϴ (0,0)] and [Pl (200 W), Vs (1500 mm/s), ϴ (0,0)] with higher compressive strength (672.78 MPa), near cortical bone elastic modulus (12.932 GPa), process-induced porosity (0.751%) and minimum surface roughness (2.72 µm). The morphology of the selective laser melted (SLMed) surface indicated that the lack of fusion pores was prominent because of low laser energy density among the laser and powder bed. Confirmatory experimentation revealed that an overall percent improvement of around 15% was found between predicted and the experimental values. Originality/value Since no significant works are available on the collaborative optimization and fine process tuning in laser powder bed fusion of biomedical Ti alloys for different load bearing implants. Therefore, this work involves the comprehensive investigation and multi-objective optimization to determine optimal parametric settings for better mechanical and physical properties. Another novel aspect is the parametric porosity simulation using Ansys Additive to assist in process parameters and their levels selection. As a result, selective laser melted Ti alloys at optimal settings may help in examining the possibility for manufacturing metallic implants for load-bearing applications.

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Section: Resultsmentioning

confidence: 99%

Manufacturability study in laser powder bed fusion of biomedical Ti alloys for orthopedic implants: an investigation of mechanical properties, process-induced porosity and surface roughness

Rehman

Wang

Ishfaq

et al. 2023

RPJ

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“…This is because the recoil pressure will directly affect the KH formation in the KH mode. [41] As shown in Figure 13b, when P r > T s , the larger recoil pressure causes the molten pool to extend downward. This will cause deep and narrow regions of the vapor cavity to collapse as the laser moves to form a KH.…”

Section: Gp and Kh Defectmentioning

confidence: 90%

Effects of Scanning Strategy on the Densification and Microhardness of Selective Laser Melting Mg–Y–Sm–Zn–Zr Alloy

Wang

et al. 2022

Adv Eng Mater

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Selective laser melting (SLM) technology is an essential technology in laser powder bed fusion (LPBF) additive manufacturing and has attracted attention because it can produce highperformance near-net-shape parts. [1] SLM technology uses computer-aided design (CAD) to model parts in three dimensions. The model was then sliced into two dimensions using the software. [2] The metal powder is laid layer-wise according to the set thickness. The high-energy laser beam melts the powder layer by layer according to a predetermined scanning path, and finally obtains complex parts. [3] Due to the advantages of high precision and low material loss, SLM technology is widely used in aerospace, biomedicine, and other fields, as well as the production of aluminum, titanium alloys, steel, and other materials. [4][5][6] Magnesium alloys are considered the lightest structural metal materials. [7] However, magnesium alloys prepared by casting will produce defects such as shrinkage cavities, pores, inclusions, and composition segregation. [8] This will limit its development. Therefore, the researchers used SLM technology to design magnesium alloy parts. This technology makes up for the shortcomings of traditional processing methods and improves the comprehensive properties of magnesium alloys. [9] The SLM processing has the characteristics of point-by-point scanning, line-by-line connection, and layer-by-layer deposition. This results in a complex thermal history and thermal cycling of the part. The energy input of the local high-energy laser beam can lead to complex molten pool flow behavior. [10] Therefore, the formed parts will generate pore defects affected by the above-mentioned complex factors. The scanning strategy directly changes the scanning path of the laser, which will affect the transmission of laser energy in the metal powder, resulting in different melting and solidification behaviors of the material, and thus has a significant impact on the type and distribution of pore defects formed in parts. [11] Guo et al. [12] compared the AlSi10Mg bulk prepared by the island and conventional scanning strategies. Concluded that the relative density of the island scanning strategy is higher than that of the conventional scanning strategy. Lu et al. [13] used the island scanning strategy to fabricate Inconel-718 blocks. The study showed that the scanning strategy with the smallest island size reduces the relative density due to the accumulation of powder on the island boundary, resulting in a higher porosity than other island sizes. Kudzal et al. [14] obtained 17-4 stainless steel tensile samples using powder bed fusion technology and explored the relationship with porosity by using different scanning strategies. The study showed that the scanning strategy would affect the type of pore defects. By comparing the island scanning strategy, zigzag scanning strategy, and remelting scanning strategy, Gu et al. [15] found that defects will appear on the surface of samples prepared by island scanning and zigzag scanning strategies. Still, ...

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“…In addition, the length has a more limited effect on the forming quality compared to the depth and width. Therefore, most reports [39][40][41][42] have focused on the effect of the depth-to-width ratio on densities and defects. In this project, the melt pool geometries at different process parameters were mainly concerned with the depth, width, and depth-to-width ratio of the melt pools.…”

Section: Simulation Of Melt Pool Geometries At Different L-pbf Proces...mentioning

confidence: 99%

Numerical Simulation of Temperature Field and Melt Pool Characteristics of CP-Ti Manufactured by Laser Powder Bed Fusion

Guo

et al. 2022

Metals

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A coupled heat source model that combined a Gauss surface heat source with a Gauss cylindrical volumetric heat source was introduced to simulate temperature field distribution and melt pool characteristics using a finite element simulation (FEM) method for the deep and narrow melt pools formed in laser powder bed fusion (L-PBF) aiming at commercial pure titanium (CP-Ti). For comparison, the same simulations using the Gauss surface heat source model and the double ellipsoid heat source model were also performed. The simulated melt pool geometries using the coupled heat source model match well with the measurements, with an average error of 1% for the melt pool depth and 7% for the width. Based on the single-track experimental results, it was found by comparing the simulated results from the three heat source models that the coupled heat source model had better accuracy than the other two. Then, the temperature field and the melt pool geometries of CP-Ti fabricated at different laser power levels from 300 W to 500 W and scanning speeds from 600 mm/s to 4000 mm/s were simulated. According to the simulated maximum temperature and geometries of the melt pool, a suitable process parameters map for CP-Ti was obtained. The reported experimental results agree well with the simulated map. The coupled heat source model is more accurate and applicable for the deep and narrow melt pools formed during L-PBF.

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Predicting the porosity defects in selective laser melting (SLM) by molten pool geometry

Cited by 53 publications

References 34 publications

Manufacturability study in laser powder bed fusion of biomedical Ti alloys for orthopedic implants: an investigation of mechanical properties, process-induced porosity and surface roughness

Manufacturability study in laser powder bed fusion of biomedical Ti alloys for orthopedic implants: an investigation of mechanical properties, process-induced porosity and surface roughness

Effects of Scanning Strategy on the Densification and Microhardness of Selective Laser Melting Mg–Y–Sm–Zn–Zr Alloy

Numerical Simulation of Temperature Field and Melt Pool Characteristics of CP-Ti Manufactured by Laser Powder Bed Fusion

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