A comprehensive study on variability of relative density in selective laser melting of Ti-6Al-4V

The aim of this study is to observe the effect of process parameters on residual stresses and relative density of Ti6Al4V samples produced by Selective Laser Melting. The investigated parameters were hatch laser power, hatch laser velocity, border laser velocity, high-temperature preheating and time delay. Residual stresses were evaluated by the bridge curvature method and relative density by the optical method. The effect of the observed process parameters was estimated by the design of experiment and surface response methods. It was found that for an effective residual stress reduction, the high preheating temperature was the most significant parameter. High preheating temperature also increased the relative density but caused changes in the chemical composition of Ti6Al4V unmelted powder. Chemical analysis proved that after one build job with high preheating temperature, oxygen and hydrogen content exceeded the ASTM B348 limits for Grade 5 titanium.

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A comprehensive study of mechanical and acoustic properties of selective laser melting material

Archives of Civil and Mechanical Engineering ◽

10.1007/s43452-019-0005-9 ◽

2019 ◽

Vol 20 (1) ◽

Cited By ~ 1

Author(s):

Claudia Barile ◽

Caterina Casavola ◽

Vincenzo Moramarco ◽

Paramsamy Kannan Vimalathithan

Keyword(s):

Selective Laser Melting ◽

Acoustic Properties ◽

Laser Melting ◽

Melting Material ◽

Comprehensive Study

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Influence of Selective Laser Melting Process Parameters on Densification Behavior, Surface Quality and Hardness of 18Ni300 Steel

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.861.77 ◽

2020 ◽

Vol 861 ◽

pp. 77-82

Author(s):

Gan Li ◽

Cheng Guo ◽

Wen Feng Guo ◽

Hong Xing Lu ◽

Lin Ju Wen ◽

...

Keyword(s):

Energy Density ◽

Relative Density ◽

Maraging Steel ◽

Surface Quality ◽

Selective Laser Melting ◽

Process Parameters ◽

Laser Power ◽

Densification Behavior ◽

Laser Melting ◽

Scan Speed

This study investigated the effect of laser power (P), scan speed (v) and hatch space (h) on densification behavior, surface quality and hardness of 18Ni300 maraging steel fabricated by selective laser melting (SLM). The results indicated that the relative density of the SLMed samples has a shape increase from 73% to 97% with the laser energy density increasing from 0.5 to 2.2 J/mm2. The relative density ≥ 99% was achieved at the energy density in the range of 2.2~5.9 J/mm2. The optimum process parameters were found to be laser power of 150~200 W, scan speed of 600mm/s and hatch space of 0.105mm. In addition, it was found that the hardness increased initially with the increasing relative density up to relative density of 90% and then little relationship, but finally increase again significantly. This work provides reference for determining process parameters for SLMed maraging steel and the development of 3D printing of die steels.

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Optimisation of selective laser melting parameters for the Ni-based superalloy IN-738 LC using Doehlert’s design

Rapid Prototyping Journal ◽

10.1108/rpj-04-2016-0063 ◽

2017 ◽

Vol 23 (5) ◽

pp. 881-892 ◽

Cited By ~ 22

Author(s):

Nataliya Perevoshchikova ◽

Jordan Rigaud ◽

Yu Sha ◽

Martin Heilmaier ◽

Barrie Finnin ◽

...

Keyword(s):

Image Analysis ◽

Relative Density ◽

Selective Laser Melting ◽

Processing Parameters ◽

Powder Alloy ◽

Operating Parameters ◽

Laser Melting ◽

Doehlert Design ◽

Feasible Set ◽

Content Type

Purpose The Ni-based superalloy IN-738 LC is known to be susceptible to porosity and different types of cracking during the build-up process and, thus, challenging to manufacture using selective laser melting (SLM). Determining a feasible set of operating parameters for SLM of nickel-based superalloys involves new approach to experimental design based on the Doehlert method that assists in determining an optimal (feasible) set of operating parameters for SLM of IN-738 LC powder alloy. Design/methodology/approach The SLM parameters are evaluated in terms of their effectiveness in obtaining the microstructure with a porosity content of <0.5 per cent and without micro-cracking. The experimental approach is exemplified with the Doehlert matrix response variable, relative density, by comparing Archimedes method with microstructural assessments of pores and cracks from image analysis. The effect of heat treatment (HT) and hot isostatic pressing (HIP) on the microstructure of the SLMed IN-738 LC powder alloy has been examined and the consequential tensile response characterised. Findings By using optimised process parameters (low heat input, medium scanning speed and small hatching distance) which provides medium energy density, samples of IN-738 LC with a macroscopic porosity <0.5 per cent and free of micro-cracks can be manufactured by SLM. The results indicate that HIP of SLMed material did not lead to a noticeable effect on mechanical properties compared to HT of SLMed material suggesting that the level of both porosity and crack density might be already below the detection limit for the mere heat-treated material. Originality/value SLM processing parameters (power, scan speed, hatching distance) for IN-738 LC were successfully optimised after only 14 experiments using Doehlert design. Two independent methods, Archimedes method and image analysis, were used in this study to assess relative density of SLM-produced samples with sets of processing parameters showing coherency in prediction with predicted response by Doehlert design.

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

10.20944/preprints202002.0225.v1 ◽

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.

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Selective Laser Melting of High Relative Density and High Strength Parts Made of Minor Surface Oxidation Treated Pure Copper Powder

Metals ◽

10.3390/met11121883 ◽

2021 ◽

Vol 11 (12) ◽

pp. 1883

Author(s):

Peng Yang ◽

Xingye Guo ◽

Dingyong He ◽

Zhen Tan ◽

Wei Shao ◽

...

Keyword(s):

Relative Density ◽

Selective Laser Melting ◽

Pure Copper ◽

Surface Oxidation ◽

High Strength ◽

Microstructural Characterization ◽

Laser Melting ◽

Oxidation Treatment ◽

High Relative Density ◽

Pure Cu

Pure Copper (Cu) is very difficult to prepare using selective laser melting (SLM) technology. This work successfully prepared the pure Cu with high relative density and high strength by the SLM technology using a surface oxidation treatment. The gas-atomized pure Cu powder was used as the feedstock in this work. Before the SLM process, the pure Cu powder was initially handled using the surface oxidation treatment to coat the powder with an extremely thin layer of Cu2O. The SLMed highly dense specimens contain α-Cu and nano-Cu2O phases. A relationship between the processing parameters (laser power (LP), scanning speed (SS), and hatch space (HS)) and density of Cu alloy in SLM was also investigated. The microstructure of SLMed Cu consists of fine grains with grain sizes ranging from 0.5 to ~30 μm. Tensile testing and detailed microstructural characterization were performed on specimens in the as-SLMed and pure copper state specimens. The mechanical property experiments showed that the specimens prepared by SLM technology containing nano-oxide phases had higher yield strength and tensile strength than that of other SLM-built pure copper. However, the elongation was remarkably decreased compared to other SLM-built pure copper, due to the fine grains and the nano-oxides.

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Investigations on Mechanical Properties of Lattice Structures with Different Values of Relative Density Made from 316L by Selective Laser Melting (SLM)

10.20944/preprints202005.0112.v1 ◽

2020 ◽

Author(s):

Paweł Płatek ◽

Judyta Sienkiewicz ◽

Jacek Janiszewski ◽

Fengchun Jiang

Keyword(s):

Relative Density ◽

Selective Laser Melting ◽

Dynamic Testing ◽

Lattice Structure ◽

Lattice Structures ◽

X Ray Diffraction ◽

Laser Melting ◽

Geometrical Quality ◽

Xrd Patterns ◽

Dynamic Loading Conditions

Nine variants of regular lattice structures with different relative densities have been designed and successfully manufactured. The produced structures have been subjected to geometrical quality control, and the manufacturability of the implemented selective laser melting SLM technique has been assessed. It was found that the dimensions of the produced lattice struts differ from those of the designed struts. These deviations depend on the direction of geometrical evaluation. Additionally, the microstructures and phase compositions of the obtained structures were characterized and compared with those of conventionally produced 316L stainless steel. The microstructure analysis and X-Ray Diffraction XRD patterns revealed a single austenite phase in the SLM samples. Both a certain broadening and a displacement of the austenite peaks were observed due to residual stresses and a crystallographic texture induced by the SLM process. Furthermore, the mechanical behavior of the lattice structure material has been defined. It was demonstrated that under both quasi-static and dynamic testing, lattice structures with high relative densities are stretch-dominated, whereas those with low relative densities are bending-dominated. Moreover, the linear relationship between the energy absorption and relative density under dynamic loading conditions has been defined

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Selective Laser Melting of 18NI-300 Maraging Steel

Materials ◽

10.3390/ma13194268 ◽

2020 ◽

Vol 13 (19) ◽

pp. 4268 ◽

Cited By ~ 1

Author(s):

Mariusz Król ◽

Przemysław Snopiński ◽

Jiří Hajnyš ◽

Marek Pagáč ◽

Dariusz Łukowiec

Keyword(s):

Relative Density ◽

Maraging Steel ◽

Selective Laser Melting ◽

Aging Treatment ◽

Steel Powder ◽

Process Conditions ◽

Laser Melting ◽

Microstructure Observation ◽

High Relative Density ◽

Wide Range

In the present study, 18% Ni 300 maraging steel powder was processed using a selective laser melting (SLM) technique to study porosity variations, microstructure, and hardness using various process conditions, while maintaining a constant level of energy density. Nowadays, there is wide range of utilization of metal technologies and its products can obtain high relative density. A dilatometry study revealed that, through heating cycles, two solid-state effects took place, i.e., precipitation of intermetallic compounds and the reversion of martensite to austenite. During the cooling process, one reaction took place (i.e., martensitic transformation), which was confirmed by microstructure observation. The improvements in the Rockwell hardness of the analyzed material from 42 ± 2 to 52 ± 0.5 HRC was improved as a result of aging treatment at 480 °C for 5 h. The results revealed that the relative density increased using laser speed (340 mm/s), layer thickness (30 µm), and hatch distance (120 µm). Relative density was found approximately 99.3%. Knowledge about the influence of individual parameters in the SLM process on porosity will enable potential manufacturers to produce high quality components with desired properties.

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