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

Materials ◽  
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.

Fundamentals of radiation heat transfer in AlSi10Mg powder bed during selective laser melting

2019 ◽  
Vol 25 (9) ◽  
pp. 1506-1515 ◽  
Author(s):  
Pei Wei ◽  
Zhengying Wei ◽  
Zhne Chen ◽  
Jun Du ◽  
Yuyang He ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Density ◽  
Negative Impact ◽  
Laser Energy ◽  
Melting Process ◽  
Laser Energy Density ◽  
Granular System ◽  
Laser Melting ◽  
Content Type ◽  
Powder Bed

Purpose This paper aims to study numerically the influence of the applied laser energy density and the porosity of the powder bed on the thermal behavior of the melt and the resultant instability of the liquid track. Design/methodology/approach A three-dimensional model was proposed to predict local powder melting process. The model accounts for heat transfer, melting, solidification and evaporation in granular system at particle scale. The proposed model has been proved to be a good approach for the simulation of the laser melting process. Findings The results shows that the applied laser energy density has a significantly influence on the shape of the molten pool and the local thermal properties. The relative low or high input laser energy density has the main negative impact on the stability of the scan track. Decreasing the porosity of the powder bed lowers the heat dissipation in the downward direction, resulting in a shallower melt pool, whereas pushing results in improvement in liquid track quality. Originality/value The randomly packed powder bed is calculated using discrete element method. The powder particle information including particle size distribution and packing density is taken into account in placement of individual particles. The effect of volumetric shrinkage and evaporation is considered in numerical model.

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

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.

Theoretical and experimental study on surface roughness of 316L stainless steel metal parts obtained through selective laser melting

2016 ◽  
Vol 22 (4) ◽  
pp. 706-716 ◽  
Author(s):  
Di Wang ◽  
Yang Liu ◽  
Yongqiang Yang ◽  
Dongming Xiao
Keyword(s):  
Surface Roughness ◽  
Energy Density ◽  
Surface Quality ◽  
Theoretical Foundation ◽  
Laser Energy ◽  
Melting Zone ◽  
Laser Energy Density ◽  
Single Track ◽  
Laser Melting ◽  
Content Type

Purpose The purpose of this paper is to provide a theoretical foundation for improving the selective laser melting (SLM) surface roughness. To improve the part’s surface quality during SLM process, the upper surface roughness of SLM parts was theoretically studied and the influencing factors were analyzed through experiments. Design/methodology/approach The characteristics of single track were first investigated, and based on the analysis of single track, theoretical value of the upper surface roughness would be calculated. Two groups of cubic sample were fabricated to validate SLM parts’ surface roughness, the Ra and relative density of all the cubic parts was measured, and the difference between theoretical calculation and experiment results was studied. Then, the effect of laser energy density on surface roughness was studied. At last, the SLM part’s surface was improved by laser re-melting method. At the end of this paper, the curved surface roughness was discussed briefly. Findings The SLM upper surface roughness is affected by the width of track, scan space and the thickness of powder layer. Measured surface roughness Ra value was about 50 per cent greater than the theoretical value. The laser energy density has a great influence on the SLM fabrication quality. Different laser energy density corresponds to different fabricating characteristics. This study divided the SLM fabrication into not completely melting zone, balling zone in low energy density, successfully fabricating zone and excessive melting zone. The laser surface re-melting (LSR) process can improve the surface roughness of SLM parts greatly without considering the fabricating time and stress accumulation. Originality/value The upper surface roughness of SLM parts was theoretically studied, and the influencing factors were analyzed together; also, the LSR process was proven to be effective to improve the surface quality. This study provides a theoretical foundation to improve the surface quality of SLM parts to promote the popularization and application of metal additive manufacturing technology.

scholarly journals Effect of Laser Energy Density on the Microstructure andTexture Evolution of Hastelloy-X Alloy Fabricated by Laser Powder Bed Fusion

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4305
Author(s):  
Shuzhe Zhang ◽  
Yunpei Lei ◽  
Zhen Chen ◽  
Pei Wei ◽  
Wenjie Liu ◽  
...  
Keyword(s):  
Grain Size ◽  
Energy Density ◽  
Electron Backscatter Diffraction ◽  
Laser Energy ◽  
Primary Dendrite ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Hastelloy X ◽  
Powder Bed ◽  
Average Grain Size

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.

Selective Laser Melting Additive Manufacturing of Novel Aluminum Based Composites With Multiple Reinforcing Phases

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Dongdong Gu ◽  
Fei Chang ◽  
Donghua Dai
Keyword(s):  
Mechanical Properties ◽  
Additive Manufacturing ◽  
Energy Density ◽  
Selective Laser Melting ◽  
Laser Energy ◽  
Laser Energy Density ◽  
Wear Property ◽  
Laser Melting ◽  
Sic Particles

The selective laser melting (SLM), due to its unique additive manufacturing (AM) processing manner and laser-induced nonequilibrium rapid melting/solidification mechanism, has a promising potential in developing new metallic materials with tailored performance. In this work, SLM of the SiC/AlSi10Mg composites was performed to prepare the Al-based composites with the multiple reinforcing phases. The influence of the SLM processing parameters on the constitutional phases, microstructural features, and mechanical performance (e.g., densification, microhardness, and wear property) of the SLM-processed Al-based composites was studied. The reinforcing phases in the SLM-processed Al-based composites included the unmelted micron-sized SiC particles, the in situ formed micron-sized Al4SiC4 strips, and the in situ produced submicron Al4SiC4 particles. As the input laser energy density increased, the extent of the in situ reaction between the SiC particles and the Al matrix increased, resulting in the larger degree of the formation of Al4SiC4 reinforcement. The densification rate of the SLM-processed Al-based composite parts increased as the applied laser energy density increased. The sufficiently high density (∼96% theoretical density (TD)) was achieved for the laser linear energy density larger than 1000 J/m. Due to the generation of the multiple reinforcing phases, the elevated mechanical properties were obtained for the SLM-processed Al-based composites, showing a high microhardness of 214 HV0.1, a considerably low coefficient of friction (COF) of 0.39, and a reduced wear rate of 1.56 × 10−5 mm3 N−1 m−1. At an excessive laser energy input, the grain size of the in situ formed Al4SiC4 reinforcing phase, both the strip- and particle-structured Al4SiC4, increased markedly. The significant grain coarsening and the formation of the interfacial microscopic shrinkage porosity lowered the mechanical properties of the SLM-processed Al-based composites. These findings in the present work are applicable and/or transferrable to other laser-based powder processing processes, e.g., laser cladding, laser metal deposition, or laser engineered net shaping.

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