18 research outputs found
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Solidification Morphology Analysis of SLM of Cu Powder
The solidification morphology analysis of fine Cu powder melted by a raster
scanned energy beam from a focused Nd:YAG laser is presented here. The powder was
processed inside of sealed chamber where it was subjected to a high vacuum cycle. The
laser fusion process consisted raster scanning a narrow rectangular pattern with a high
density of scanning lines, the chamber was purged with inert gas during the process. Up
to a 3.3 mm/s laser travel speed and maximum laser power level of 240 W were used to
melt a 2 mm thick bed of loose powder. The resulting solidified ingots were separated
into categories based on their shape integrity. Metallographic analysis by means of
optical microscopy and scanning electron microscopy was performed on the cross section
and longitudinal section of the ingots with homogeneous surface and complete shape
integrity. Characterization revealed an elongated columnar grain structure with a grain
orientation along the direction of the laser travel direction, some degree of porosity was
observed too in some of the specimens. It was observed that grains diameter ranged from
10 to 100 µm and contained a two phase eutectic microstructure of copper and it oxides.
Oxygen content was accounted from a 5.5 up to 8.1 atomic percent, a small percentage of
chlorine was present, too. A 2 to 8 percent variation in the Vickers microhardness values
were found between the different specimens when measured along the longitudinal
section. These HV values corresponded to approximate 20-25% cold rolled oxygen free
copper (80-90 HV). The ingots thus produced suggest that a multilayer structure from Cu
powder could be build by the SLM process having sufficiently adequate compositional,
microstructure and mechanical properties for functional applications.Mechanical Engineerin
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Direct Metal Laser Fabrication of Cu Slabs from Powder Precursor: Surface Depth of Melt and Furnace Temperature Issues
A DMLF processing unit based on a raster-scanned 80 W CO2 laser beam has been
developed to process single layers of metallic powder precursor. The process chamber
provides atmosphere control (high vacuum and inert gas refill) besides temperature
elevation up to 700 o
C. In this work, copper powder precursor is confined inside a
refractory steel mask surrounded by an aluminum oxide jacket that acts as insulator. The
powder layers can have thicknesses of 0,5 and 1 mm. An infrared pyrometer measures
in real time the temperature at one location in the surface of the powder bed. Scan
speed, scan step, and furnace temperature have been varied to find combinations of such
parameters that render surface melting and maximum densification. Partially melted
samples were produced and their mass density was measured. Micro-hardness and
surface roughness were also measured along the resolidified surface, the first rendering
an average of 80,6 HV compared to the 90-105 HV of oxygen free copper, while the
second resulting in an 8 μm Ra value. Maximum melt of depth achieved is ~0,15 mm
followed by a sintered layer.Mechanical Engineerin
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Mechanical Behavior of SLS Components in Relation to the Build Orientation During the Sintering Process as Measured by ESPI
Selective Laser Sintering (SLS) allows producing real parts from CAD data from materials with
different characteristics compared to the final model, presenting dissimilar mechanical properties
between the prototype and the product. The purpose of this work is to correlate the mechanical
behavior of beam-type specimens produced by SLS with build orientation angle used as a process
parameter, also attempting to demonstrate how this parameter affects the accuracy of the
Empirical Similitude Method (ESM). ESM presents itself as a valuable tool when creating scale
models with SLS, specifically in the framework of evolutionary product design. More
specifically, the Young modulus variation of test specimens of well-known dimensions and
material (DuraformTM PA2
), will be characterized by loading them within the elastic range. The
resulting elastic deformations will be measured using the technique of Electronic Speckle Pattern
Interferometry (ESPI) for small deformations in an out-of-plane configuration, contrasting these
results with the elastic theory of deformations. As a main result, it was found that there exists a
linear correlation between the build angle and the elastic modulus of the parts. Secondly, it was
demonstrated empirically that the ESM predicts better the mechanical response of the part than
TSM. Moreover, a 30% error reduction can be achieved within the ESM when using the build
orientation angle as a process parameter.Mechanical Engineerin
Diseño y construcción de un equipo de soldadura por fricción con asistencia láser para la unión de ejes de acero AISI 1045 y aluminio 2017-T4
Welding metal alloys with dissimilar melting points make conventional welding processes unfeasible to be used. On the other hand, friction welding has proven to be a promising technology capable of joining materials, while preventing the temperature from exceeding the melting point. However, obtaining a welded joint with mechanical properties that are similar to the base materials remains a challenge. In the development of this work, a laser-assisted rotary friction welding equipment was designed and manufactured. A 3 HP conventional lathe was used to provide rotary movement, and a hydraulic pressure system that applies axial force through a simple effect cylinder was designed to generate friction to obtain the union between the base materials. In the implemented equipment, joints of AISI 1045 steel and 2017-T6 aluminum shafts were made. The welded joints were metallurgically evaluated, emphasizing on the chemical composition at the weld interface. For microstructure characterization, scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), and glow discharge optical emission spectrometry (GDOES) were used to measure the initial composition of the welded materials. The results obtained show an adequate joint between the base materials, denoting the usefulness of the equipment manufactured for the union of dissimilar materials.La soldadura de materiales disímiles hace que los procesos de soldadura convencional no sean factibles de ser utilizados. La soldadura por fricción, por otro lado, ha demostrado ser una tecnología prometedora capaz de unir materiales sin que la temperatura supere su punto de fusión. Sin embargo, la obtención de las propiedades mecánicas de la junta soldada con características similares a los materiales base sigue siendo un desafío. En el desarrollo de este trabajo se diseñó y fabricó un equipo de soldadura por fricción rotatoria con asistencia láser. Para proporcionar el movimiento rotatorio se empleó un torno convencional de 3 HP de potencia y para generar fricción se diseñó un sistema hidráulico de presión el cual aplica fuerza axial mediante un cilindro de simple efecto para obtener la unión entre los materiales base. En el equipo implementado se realizaron uniones de ejes de acero AISI 1045 con aluminio 2017-T6; las uniones soldadas se evaluaron metalúrgicamente, haciendo hincapié en la composición química en la interfaz de la soldadura. Para la caracterización de la microestructura se empleó microscopía electrónica de barrido (SEM), espectroscopía de dispersión de energía (EDS) y espectrometría de emisión óptica de descarga luminiscente (GDOES) para medir la composición inicial de los materiales que se soldaron. Los resultados obtenidos muestran una adecuada unión entre los materiales base, denotando la utilidad del equipo fabricado para la unión de materiales disimiles
Diseño y construcción de un equipo de soldadura por fricción con asistencia láser para la unión de ejes de acero AISI 1045 y aluminio 2017-T4
La soldadura de materiales disímiles hace que los
procesos de soldadura convencional no sean factibles
de ser utilizados. La soldadura por fricción, por otro
lado, ha demostrado ser una tecnología prometedora
capaz de unir materiales sin que la temperatura supere
su punto de fusión. Sin embargo, la obtención
de las propiedades mecánicas de la junta soldada con
características similares a los materiales base sigue
siendo un desafío. En el desarrollo de este trabajo
se diseñó y fabricó un equipo de soldadura por fricción
rotatoria con asistencia láser. Para proporcionar
el movimiento rotatorio se empleó un torno convencional
de 3 HP de potencia y para generar fricción se
diseñó un sistema hidráulico de presión el cual aplica
fuerza axial mediante un cilindro de simple efecto
para obtener la unión entre los materiales base. En el equipo implementado se realizaron uniones
de ejes de acero AISI 1045 con aluminio 2017-T6;
las uniones soldadas se evaluaron metalúrgicamente,
haciendo hincapié en la composición química en la
interfaz de la soldadura. Para la caracterización de
la microestructura se empleó microscopía electrónica
de barrido (SEM), espectroscopía de dispersión de
energía (EDS) y espectrometría de emisión óptica de
descarga luminiscente (GDOES) para medir la composición
inicial de los materiales que se soldaron. Los
resultados obtenidos muestran una adecuada unión
entre los materiales base, denotando la utilidad del
equipo fabricado para la unión de materiales disimiles.//Welding metal alloys with dissimilar melting points
make conventional welding processes unfeasible to
be used. On the other hand, friction welding has
proven to be a promising technology capable of joining
materials, while preventing the temperature from
exceeding the melting point. However, obtaining a
welded joint with mechanical properties that are similar
to the base materials remains a challenge. In
the development of this work, a laser-assisted rotary
friction welding equipment was designed and manufactured.
A 3 HP conventional lathe was used to
provide rotary movement, and a hydraulic pressure
system that applies axial force through a simple effect
cylinder was designed to generate friction to obtain
the union between the base materials. In the implemented equipment, joints of AISI 1045
steel and 2017-T6 aluminum shafts were made. The
welded joints were metallurgically evaluated, emphasizing
on the chemical composition at the weld interface.
For microstructure characterization, scanning
electron microscopy (SEM), energy dispersion spectroscopy
(EDS), and glow discharge optical emission
spectrometry (GDOES) were used to measure the initial
composition of the welded materials. The results
obtained show an adequate joint between the base
materials, denoting the usefulness of the equipment
manufactured for the union of dissimilar materials
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Surface modification of ceramic and metallic alloy substrates by laser raster-scanning
This work describes the feasibility of continuous wave laser-raster scanprocessing under controlled atmospheric conditions as employed in three distinct
surface modification processes: (a) surface roughness reduction of indirect-Selective
Laser Sintered 420 martensitic stainless steel–40 wt. % bronze infiltrated surfaces (b)
Si-Cr-Hf-C coating consolidation over 3D carbon–carbon composites cylinders (c)
dendritic solidification structures of Mar–M 247 confined powder precursor grown
from polycrystalline Alloy 718 substrates. A heat transfer model was developed to
illustrate that the aspect ratio of the laser scanned pattern and the density of scanning
lines play a significant role in determining peak surface temperature, heating and
cooling rates and melt resident times. Comprehensive characterization of the surface
of the processed specimens was performed using scanning electron microscopy
viii
(SEM), energy dispersive spectroscopy (EDS), optical metallography, X-ray
diffraction (XRD), and, in certain cases, tactile profilometry. In Process (a), it was
observed that a 24 % to 37 % roughness Ra reduction could be accomplished from the
as-received value of 2.50+/-0.10 microns for laser energy densities ranging from 350
to 500 J/cm2
. In Process (b), complete reactive wetting of carbon-carbon composite
cylinders surface was achieved by laser melting a Si-Cr-Hf-C slurry. Coatings
showed good thermal stability at 1000ºC in argon, and, when tested in air, a percent
weight reduction rate of -6.5 wt.%/hr was achieved. A soda-glass overcoat applied
over the coated specimens by conventional means revealed a percent weight
reduction rate between -1.4 to -2.2 wt.%/hr. Finally, in Process (c), microstructure of
the Mar-M 247 single layer deposits, 1 mm in height, grown on Alloy 718
polycrystalline sheets, resulted in a sound metallurgical bond, low porosity, and
uniform thickness. Polycrystalline dendrites grew preferentially along the [001]
direction from the substrate up to 400 microns. Above that height, dendrites appear to
shift towards the [100] growth direction driven by the thermal gradient and
solidification front velocity. This research demonstrated that surface modification by
high-speed raster-scanning a high power laser beam under controlled atmospheric
conditions is a feasible and versatile technique that can accomplish diverse purposes
involving metallic as well as ceramic surfaces.This work describes the feasibility of continuous wave laser-raster scanprocessing under controlled atmospheric conditions as employed in three distinct
surface modification processes: (a) surface roughness reduction of indirect-Selective
Laser Sintered 420 martensitic stainless steel–40 wt. % bronze infiltrated surfaces (b)
Si-Cr-Hf-C coating consolidation over 3D carbon–carbon composites cylinders (c)
dendritic solidification structures of Mar–M 247 confined powder precursor grown
from polycrystalline Alloy 718 substrates. A heat transfer model was developed to
illustrate that the aspect ratio of the laser scanned pattern and the density of scanning
lines play a significant role in determining peak surface temperature, heating and
cooling rates and melt resident times. Comprehensive characterization of the surface
of the processed specimens was performed using scanning electron microscopy
viii
(SEM), energy dispersive spectroscopy (EDS), optical metallography, X-ray
diffraction (XRD), and, in certain cases, tactile profilometry. In Process (a), it was
observed that a 24 % to 37 % roughness Ra reduction could be accomplished from the
as-received value of 2.50+/-0.10 microns for laser energy densities ranging from 350
to 500 J/cm2
. In Process (b), complete reactive wetting of carbon-carbon composite
cylinders surface was achieved by laser melting a Si-Cr-Hf-C slurry. Coatings
showed good thermal stability at 1000ºC in argon, and, when tested in air, a percent
weight reduction rate of -6.5 wt.%/hr was achieved. A soda-glass overcoat applied
over the coated specimens by conventional means revealed a percent weight
reduction rate between -1.4 to -2.2 wt.%/hr. Finally, in Process (c), microstructure of
the Mar-M 247 single layer deposits, 1 mm in height, grown on Alloy 718
polycrystalline sheets, resulted in a sound metallurgical bond, low porosity, and
uniform thickness. Polycrystalline dendrites grew preferentially along the [001]
direction from the substrate up to 400 microns. Above that height, dendrites appear to
shift towards the [100] growth direction driven by the thermal gradient and
solidification front velocity. This research demonstrated that surface modification by
high-speed raster-scanning a high power laser beam under controlled atmospheric
conditions is a feasible and versatile technique that can accomplish diverse purposes
involving metallic as well as ceramic surfaces.Materials Science and Engineerin
Surface roughness Ra prediction in Selective Laser Melting of 316L stainless steel by means of artificial intelligence inference
Selective Laser Melting (SLM) is a widely used metal additive manufacturing process due to the possibility of elaborating complicated and customized tridimensional parts or components. This paper presents research on predicting surface roughness of 316L stainless steel manufactured SLM parts using the well-known multilayer perceptron (MLP) and an adaptive neuro-fuzzy inference system (ANFIS). Two models were adjusted to predict the top surface quality for different values of laser power, scanning speed, and hatch distance. The obtained results were evaluated and compared in order to ensure the goodness of fit of both techniques. The multilayer perceptron-based model has proved, to possess better predictive capability of the non-linear relationships of the SLM process. However, adequate results were also obtained with the adjusted ANFIS. The consistency of the presented models is also compared with previously published empirical formulations and discussed. As a final result, has been demonstrated that both fitted models outperform the previously published statistic-based approaches