Effects of laser-energy density and build orientation on the structure–property relationships in as-built Inconel 718 manufactured by laser powder bed fusion

It is of great importance to study the microstructure and textural evolution of laser powder bed fusion (LPBF) formed Hastelloy-X alloys, in order to establish a close relationship between the process, microstructure, and properties through the regulation of the Hastelloy-X formation process parameters. In this paper, components of a Hastelloy-X alloy were formed with different laser energy densities (also known as the volume energy density VED). The densification mechanism of Hastelloy-X was studied, and the causes of defects, such as pores and cracks, were analyzed. The influence of different energy densities on grain size, texture, and orientation was investigated using an electron backscatter diffraction technique. The results show that the average grain size, primary dendrite arm spacing, and number of low angle grain boundaries increased with the increase of energy density. At the same time, the VED can strengthen the texture. The textural intensity increases with the increase of energy density. The best mechanical properties were obtained at the VED of 96 J·mm−3.

Download Full-text

Process–Structure–Property Relationships of Copper Parts Manufactured by Laser Powder Bed Fusion

Materials ◽

10.3390/ma14112945 ◽

2021 ◽

Vol 14 (11) ◽

pp. 2945

Author(s):

Mohamed Abdelhafiz ◽

Kassim S. Al-Rubaie ◽

Ali Emadi ◽

Mohamed A. Elbestawi

Keyword(s):

Laser Power ◽

Scanning Speed ◽

Powder Bed Fusion ◽

Structure Property ◽

Laser Powder Bed Fusion ◽

Powder Bed ◽

X Ray ◽

Structure Property Relationships ◽

Process Structure ◽

Hatch Spacing

The process–structure–property relationships of copper laser powder bed fusion (L-PBF)-produced parts made of high purity copper powder (99.9 wt %) are examined in this work. A nominal laser beam diameter of 100 μm with a continuous wavelength of 1080 nm was employed. A wide range of process parameters was considered in this study, including five levels of laser power in the range of 200 to 370 W, nine levels of scanning speed from 200 to 700 mm/s, six levels of hatch spacing from 50 to 150 μm, and two layer thickness values of 30 μm and 40 μm. The influence of preheating was also investigated. A maximum relative density of 96% was obtained at a laser power of 370 W, scanning speed of 500 mm/s, and hatch spacing of 100 μm. The results illustrated the significant influence of some parameters such as laser power and hatch spacing on the part quality. In addition, surface integrity was evaluated by surface roughness measurements, where the optimum Ra was measured at 8 μm ± 0.5 μm. X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX) were performed on the as-built samples to assess the impact of impurities on the L-PBF part characteristics. The highest electrical conductivity recorded for the optimum density-low contaminated coils was 81% IACS.

Download Full-text

Process-structure-property relationships in laser powder bed fusion of permanent magnetic Nd-Fe-B

Materials & Design ◽

10.1016/j.matdes.2021.109992 ◽

2021 ◽

pp. 109992

Author(s):

Julan Wu ◽

Nesma T. Aboulkhair ◽

Michele Degano ◽

Ian Ashcroft ◽

Richard J.M. Hague

Keyword(s):

Powder Bed Fusion ◽

Structure Property ◽

Laser Powder Bed Fusion ◽

Powder Bed ◽

Structure Property Relationships ◽

Process Structure

Download Full-text

Machinability of INCONEL718 Alloy with a Porous Microstructure Produced by Laser Melting Powder Bed Fusion at Higher Energy Densities

Materials ◽

10.3390/ma13245730 ◽

2020 ◽

Vol 13 (24) ◽

pp. 5730

Author(s):

Paul Wood ◽

Antonio Díaz-Álvarez ◽

José Díaz-Álvarez ◽

María Henar Miguélez ◽

Alexis Rusinek ◽

...

Keyword(s):

Energy Density ◽

Laser Energy ◽

Cutting Speed ◽

Machining Process ◽

Laser Energy Density ◽

Powder Bed Fusion ◽

Laser Melting ◽

Powder Bed ◽

Orthogonal Turning ◽

Different Levels

Products produced by additive manufacturing (AM) seek to exploit net shape manufacturing by eliminating or minimizing post-process stages such as machining. However, many applications which include turbo machinery components with tight dimensional tolerances and a smooth surface finish will require at least a light machine finishing stage. This paper investigates the machinability of the additively fabricated INCONEL718 (IN718) alloy produced by laser melting powder bed fusion (LM-PBF) with different levels of spherical porosity in the microstructure. The literature suggests that the band width for laser energy density, which combines the various scan process parameters to obtain a low spherical type porosity in the LM-PBF IN718 alloy (~1%), has wide breadth. With the increasing laser energy density and above a threshold, there is a rapid increase in the spherical pore size. In this paper, three tube samples each with different levels of spherical porosity were fabricated by varying the laser energy density for LM-PBF of the IN718 alloy within the stable and higher energy density range and the porosity measured. A low laser energy density was avoided due to balling up, which promotes highly irregular lack of fusion defects and poor consolidation within the alloy microstructure. An orthogonal turning test instrumented, with a three-component dynamometer to measure the cutting forces, was performed on AM produced IN718 tube samples under light cut conditions to simulate a finish machining process. The orthogonal turning tests were also performed on a tube sample obtained from the wrought extruded stock. The machining process parameters, which were studied include varying the cutting speed at three levels, at a fixed feed and under dry cut conditions for a short duration to avoid the tool wear. The results obtained were discussed and a notable finding was the higher rate of built-up-edge formation on the tool tip from the AM samples with a higher porosity and especially at a higher cutting speed. The paper also discusses the mechanisms that underpin the findings.

Download Full-text

Effect of Laser Energy Density on Bulk Properties of SS 316L Structures Built by Laser Additive Manufacturing Using Powder Bed Fusion

Volume 2: Combustion, Fuels, and Emissions; Renewable Energy: Solar and Wind; Inlets and Exhausts; Emerging Technologies: Hybrid Electric Propulsion and Alternate Power Generation; GT Operation and Maintenance; Materials and Manufacturing (Including Coatings, Composites, CMCs, Additive Manufacturing); Analytics and Digital Solutions for Gas Turbines/Rotating Machinery ◽

10.1115/gtindia2019-2452 ◽

2019 ◽

Author(s):

Saurav K. Nayak ◽

Sanjay K. Mishra ◽

Christ P. Paul ◽

Arackal N. Jinoop ◽

Sunil Yadav ◽

...

Keyword(s):

Additive Manufacturing ◽

Energy Density ◽

Layer Thickness ◽

Laser Energy ◽

Advanced Technology ◽

Incomplete Fusion ◽

Laser Energy Density ◽

Powder Bed Fusion ◽

Laser Additive Manufacturing ◽

Powder Bed

Abstract Laser Additive Manufacturing using Powder Bed Fusion (LAM-PBF) is one of the revolutionary technologies playing a key role in fourth industrial revolution for redefining manufacturing from mass production to mass customization. To upkeep the pace, Raja Ramanna Centre for Advanced Technology (RRCAT) has indigenously developed an LAM-PBF system and it is being used for process and component development for various engineering applications. This paper reports a parametric investigation to evaluate the influence of process parameters on the sample properties and to develop the process window for fabricating complex shaped engineering components. In the present work, an experimental investigation is carried out to investigate the effect of Laser Energy density (LED) on the porosity, microstructure and mechanical properties of SS 316L bulk structures fabricated by LAM-PBF system. LED is a combined parameter simultaneously considering the effect of Laser Power (P), Scan Speed (v), hatch spacing (h) and layer thickness (t). The effect of three LED values such as 83.33 J/mm3, 253.97 J/mm3 and 476.19 J/mm3 is investigated in the present work by building cuboidal samples at a layer thickness of 75 microns. Porosity is estimated using area fraction method in optical microscopy and it is found that the minimum porosity of 0.14 % and pore area of 1.28 mm2 are observed at 253.97 J/mm3. Maximum porosity of 18.85 % is observed at 83 J/mm3 due to incomplete fusion defects. However, porosity observed at 475 J/mm3 is 6.56 % with average pore size of 17.8 mm2. Microstructural studies show primarily columnar growth in all the samples with fine dendrites. The dendrite size is observed to be 3.2 μm, 2.4 μm and 1.46 μm at 83.33 J/mm3, 253.97 J/mm3 and 476.19 J/mm3 respectively. Micro-hardness and single cycle automatic ball indentation studies are found to be in agreement with dendritic size, with lower hardness at larger dendrite size. X-Ray Diffraction (XRD) studies indicate similar peaks at all the conditions, with slight peak shift observed with increase in LED primarily due to higher amount of residual stress. Thus, it can be inferred that LED of 253.97 J/mm3 is suitable for fabricating engineering components due to combination of lower porosity and fine dendritic structure.

Download Full-text

Mapping of residual stresses in as-built Inconel 718 fabricated by laser powder bed fusion: A neutron diffraction study of build orientation influence on residual stresses

Additive Manufacturing ◽

10.1016/j.addma.2020.101501 ◽

2020 ◽

Vol 36 ◽

pp. 101501

Author(s):

Prabhat Pant ◽

Sebastian Proper ◽

Vladimir Luzin ◽

Sören Sjöström ◽

Kjell Simonsson ◽

...

Keyword(s):

Neutron Diffraction ◽

Residual Stresses ◽

Diffraction Study ◽

Inconel 718 ◽

Neutron Diffraction Study ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Powder Bed ◽

Build Orientation

Download Full-text

A Novel Required Laser Energy Predicting Model for Laser Powder Bed Fusion

Metals ◽

10.3390/met11121966 ◽

2021 ◽

Vol 11 (12) ◽

pp. 1966

Author(s):

Yang Liu ◽

Mingxuan Li ◽

Xiaofeng Lu ◽

Xiaolei Zhu ◽

Peng Li

Keyword(s):

Heat Transfer ◽

Energy Density ◽

Laser Energy ◽

Great Influence ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Predicting Model ◽

Powder Bed ◽

The Relationship

During the process of laser powder bed fusion (LPBF) printing, the energy of heat input have a great influence on the quality of fabricated specimens. In this paper, based on the heat transfer and metallurgical mechanism, a theoretical predicting model of the required laser energy to fabricate high-density LPBF components was established. The theoretical required laser energy density of AlSi10Mg, TC4 and 316L were calculated, which are 51.74 J/mm3, 104.48 J/mm3 and 69.28 J/mm3, respectively. By comparing with the experimental results in the references, it was found that the errors between them are within 10%. In addition, this article discussed the relationship between the VED and the specimen defects, and found that the changing in the VED will alter the types of specimen defects.

Download Full-text

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.

Download Full-text