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Laser additive manufacturing of oxide dispersion strengthened steels using laser-generated nanoparticle-metal composite powders

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ScienceDirect
Procedia CIRP 00 (2017) 000–000
www.elsevier.com/locate/procedia
2212-8271 © 2017 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the scientific committee of the 28th C IRP Design Conference 2018.
28th CIRP Design Conference, May 2018, Nantes, France
A new methodology to analyze the functional and physical architecture of
existing products for an assembly oriented product family identification
Paul Stief *, Jean-Yves Dantan, Alain Etienne, Ali Siadat
École Nationale Supérieure d’Arts et Métiers, Arts et Métiers ParisTech, LCFC EA 4495, 4 Rue Augustin Fresnel, Metz 57078, France
* Corresponding author. Tel.: +33 3 87 37 54 30; E-mail address: paul.stief@ensam.eu
Abstract
In today’s business environment, the trend towards more product variety and customization is unbroken. Due to this development, the need of
agile and reconfigurable production systems emerged to cope with various products and product families. To design and optimize production
systems as well as to choose the optimal product matches, product analysis methods are needed. Indeed, most of the known methods aim to
analyze a product or one product family on the physical level. Different product families, however, may differ largely in terms of the number and
nature of components. This fact impedes an efficient comparison and choice of appropriate product family combinations for the production
system. A new methodology is proposed to analyze existing products in view of their functional and physical architecture. The aim is to cluster
these products in new assembly oriented product families for the optimization of existing assembly lines and the creation of future reconfigurable
assembly systems. Based on Datum Flow Chain, the physical structure of the products is analyzed. Functional subassemblies are identified, and
a functional analysis is performed. Moreover, a hybrid functional and physical architecture graph (HyFPAG) is the output which depicts the
similarity between product families by providing design support to both, production system planners and product designers. An illustrative
example of a nail-clipper is used to explain the proposed methodology. An industrial case study on two product families of steering columns of
thyssenkrupp Presta France is then carried out to give a first industrial evaluation of the proposed approach.
© 2017 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the scientific committee of the 28th CIRP Design Conference 2018.
Keywords: Assembly; Design method; Family identification
1. Introduction
Due to the fast development in the domain of
communication and an ongoing trend of digitization and
digitalization, manufacturing enterprises are facing important
challenges in today’s market environments: a continuing
tendency towards reduction of product development times and
shortened product lifecycles. In addition, there is an increasing
demand of customization, being at the same time in a global
competition with competitors all over the world. This trend,
which is inducing the development from macro to micro
markets, results in diminished lot sizes due to augmenting
product varieties (high-volume to low-volume production) [1].
To cope with this augmenting variety as well as to be able to
identify possible optimization potentials in the existing
production system, it is important to have a precise knowledge
of the product range and characteristics manufactured and/or
assembled in this system. In this context, the main challenge in
modelling and analysis is now not only to cope with single
products, a limited product range or existing product families,
but also to be able to analyze and to compare products to define
new product families. It can be observed that classical existing
product families are regrouped in function of clients or features.
However, assembly oriented product families are hardly to find.
On the product family level, products differ mainly in two
main characteristics: (i) the number of components and (ii) the
type of components (e.g. mechanical, electrical, electronical).
Classical methodologies considering mainly single products
or solitary, already existing product families analyze the
product structure on a physical level (components level) which
causes difficulties regarding an efficient definition and
comparison of different product families. Addressing this
Procedia CIRP 74 (2018) 196–200
2212-8271 © 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(https://creativecommons.org/licenses/by-nc-nd/4.0/)
Peer-review under responsibility of the Bayerisches Laserzentrum GmbH.
10.1016/j.procir.2018.08.093
© 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(https://creativecommons.org/licenses/by-nc-nd/4.0/)
Peer-review under responsibility of the Bayerisches Laserzentrum GmbH.
Available online at www.sciencedirect.com
ScienceDirect
Procedia CIRP 00 (2018) 000–000
www.elsevier.com/locate/procedia
2212-8271 © 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/3.0/)
Peer-review under responsibility of the Bayerisches Laserzentrum GmbH.
10th CIRP Conference on Photonic Technologies [LANE 2018]
Laser additive manufacturing of oxide dispersion strengthened steels using
laser-generated nanoparticle-metal composite powders
Markus B. Wilmsa, RenéStreubelb, Felix Frömelc, Andreas Weisheita, Jochen Tenkampc,
Frank Waltherc,Stephan Barcikowskib,Johannes Henrich Schleifenbauma, Bilal Gökceb,*
aChair for Digital Additive Production (DAP), RWTH Aachen University and Fraunhofer Institue of Laser Technology (ILT), 52074 Aachen, Germany
bTechnical Chemistry I and Center for Nanointegration Duisburg-Essen (CENIDE), University Duisburg-Essen, 45141 Essen, Germany
cTU Dortmund University, Department of Materials Test Engineering (WPT), Baroper Str. 303, D-44227 Dortmund, Germany
* Corresponding author. Tel.: +49-201-183-3146; fax: +49-201-183-3049.E-mail address: bilal.goekce@uni-due.de
Abstract
A new route for the synthesis of powder composites suitable for processing with laser additive manufacturing is demonstrated. The powder
composites, consisting of micrometer-sized stainless steel powder, homogenously decorated with nano-scaled Y2O3powder particles, are
manufactured by laser processing of colloids and electrostatic deposition. Consolidated by laser metal deposition and selective laser melting,
the resulting specimens show superior mechanical properties at elevated temperatures, caused by the nano-sized, homogenously distributed
dispersoids.
© 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/3.0/)
Peer-review under responsibility of the Bayerisches Laserzentrum GmbH.
Keywords: Oxide dispersion strengthened materials; ODS; Laser additive manufacturing; Pulsed laser ablation in liquids; Selective Laser Melting
1. Introduction
Oxide dispersion steels are a promising structural material
class for GenIV nuclear reactorsas well as future fusion
reactors [1, 2]. This material class is typically composed of a
ferritic/martensitic steel matrix, alloyed with high amounts of
chromium (9-20%) to exhibit corrosion resistance. The steel
matrix is additionally reinforced with nanometer-sized
dispersoids, composed of titanium-containing yttrium-based
oxides [3,4], exhibiting low solubility in the steel matrix
offering only low potential for coarsening by Ostwald
ripening [5]. The homogeneously distributed dispersoids
increase material strength in particular at high temperatures,
such as creep resistance [8,9]. Additionally, theyact as sinks
for defects, induced by high-energy neutron or ion irradiation,
and therefore increase the resistance against macroscopic
material degradation, such as swelling [10-12].
The main fabrication route for ODS steels is the powder
metallurgy route, consisting of a long-term (up to 48h), batch-
wise mechanical alloying process that uses metal matrix alloy
powder and a nanometer-sized yttrium oxide powder [13-15].
By ball milling in planetary or high-energy attritor type mills
powder composites of metal and oxide particles are formed.
This process is characterized by the dissolution of oxide
particles into the metal powders, since the peak of yttrium
oxide in XRD disappears with prolonged milling times [16].
The ball milling process is subsequently followed by various
types of consolidation processes, such as hot-isostatic pressing
or hot extrusion as well as various thermomechanical
treatments in order to adjust the final microstructure of the
alloy. The complex and expensive fabrication route for ODS
Available online at www.sciencedirect.com
ScienceDirect
Procedia CIRP 00 (2018) 000–000
www.elsevier.com/locate/procedia
2212-8271 © 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/3.0/)
Peer-review under responsibility of the Bayerisches Laserzentrum GmbH.
10th CIRP Conference on Photonic Technologies [LANE 2018]
Laser additive manufacturing of oxide dispersion strengthened steels using
laser-generated nanoparticle-metal composite powders
Markus B. Wilmsa, RenéStreubelb, Felix Frömelc, Andreas Weisheita, Jochen Tenkampc,
Frank Waltherc,Stephan Barcikowskib,Johannes Henrich Schleifenbauma, Bilal Gökceb,*
aChair for Digital Additive Production (DAP), RWTH Aachen University and Fraunhofer Institue of Laser Technology (ILT), 52074 Aachen, Germany
bTechnical Chemistry I and Center for Nanointegration Duisburg-Essen (CENIDE), University Duisburg-Essen, 45141 Essen, Germany
cTU Dortmund University, Department of Materials Test Engineering (WPT), Baroper Str. 303, D-44227 Dortmund, Germany
* Corresponding author. Tel.: +49-201-183-3146; fax: +49-201-183-3049.E-mail address: bilal.goekce@uni-due.de
Abstract
A new route for the synthesis of powder composites suitable for processing with laser additive manufacturing is demonstrated. The powder
composites, consisting of micrometer-sized stainless steel powder, homogenously decorated with nano-scaled Y2O3powder particles, are
manufactured by laser processing of colloids and electrostatic deposition. Consolidated by laser metal deposition and selective laser melting,
the resulting specimens show superior mechanical properties at elevated temperatures, caused by the nano-sized, homogenously distributed
dispersoids.
© 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/3.0/)
Peer-review under responsibility of the Bayerisches Laserzentrum GmbH.
Keywords: Oxide dispersion strengthened materials; ODS; Laser additive manufacturing; Pulsed laser ablation in liquids; Selective Laser Melting
1. Introduction
Oxide dispersion steels are a promising structural material
class for GenIV nuclear reactorsas well as future fusion
reactors [1, 2]. This material class is typically composed of a
ferritic/martensitic steel matrix, alloyed with high amounts of
chromium (9-20%) to exhibit corrosion resistance. The steel
matrix is additionally reinforced with nanometer-sized
dispersoids, composed of titanium-containing yttrium-based
oxides [3,4], exhibiting low solubility in the steel matrix
offering only low potential for coarsening by Ostwald
ripening [5]. The homogeneously distributed dispersoids
increase material strength in particular at high temperatures,
such as creep resistance [8,9]. Additionally, theyact as sinks
for defects, induced by high-energy neutron or ion irradiation,
and therefore increase the resistance against macroscopic
material degradation, such as swelling [10-12].
The main fabrication route for ODS steels is the powder
metallurgy route, consisting of a long-term (up to 48h), batch-
wise mechanical alloying process that uses metal matrix alloy
powder and a nanometer-sized yttrium oxide powder [13-15].
By ball milling in planetary or high-energy attritor type mills
powder composites of metal and oxide particles are formed.
This process is characterized by the dissolution of oxide
particles into the metal powders, since the peak of yttrium
oxide in XRD disappears with prolonged milling times [16].
The ball milling process is subsequently followed by various
types of consolidation processes, such as hot-isostatic pressing
or hot extrusion as well as various thermomechanical
treatments in order to adjust the final microstructure of the
alloy. The complex and expensive fabrication route for ODS
10th CIRP Conference on Photonic Technologies [LANE 2018]
Markus B. Wilms et al. / Procedia CIRP 74 (2018) 196–200 197
2Author name /Procedia CIRP 00 (2018) 000000
steels still poses the main drawback for widespread industrial
applications of these type of materials. Also, conventional
techniques do not offer the possibility of near net shaped
manufacturing. An alternative manufacturing method is Laser
Additive Manufacturing (LAM), which is principally capable
of producing ODS materials by offering high solidification
rates in combination with strong Maragoni forces within small
scaled melt pools. The principalcapability of the LAM
processes Laser Metal Deposition (LMD) [17]and Selective
Laser Melting (SLM) [18-20]to produce ODS materials has
been showed in various studies. However, in all cases
mechanically alloyed powder has been utilized.In this study
the feasibility of nanoparticle-metal powder composites,
fabricated by a new route consisting of laser processing of
colloids (LPC) and subsequent adsorption by pH-controlled
electrostatic interaction on steel powders [21] for the LAM
production of ODS materials is demonstrated. Mechanical
characterization is performed by compression tests of
specimens manufactured by LMD [22]. Additionally the
powder was used to manufacture bulk specimens via SLM.
2. Materials and Methods
Ferritic, stainless steel powder (Nanoval) consisting of
21.03 wt% Cr, 4.67 wt% Al and 0.47 wt% Ti and with two
powder particle fractions of < 45 μm for SLM and 45-90 μm
for LMD was used for laser-based processing of colloids with
0.3 wt% commercial Y2O3nanopowder (Sigma Aldrich).
2.1 Production of composite powders
A 10 ps laser (EdgeWave) with a wavelength of 355 nm
was used with a laser power of 20 W and a repetition rate of
80 kHz to deagglomerate dispersed Y2O3nanoparticles in an
aqueous solution by laser processing of colloids (LPC)
[23,24]via a flow jet configuration [25,26] (Fig. 1) for five
passage cycles. The nanoparticles are adsorbed via
electrostatic interaction by adjusting the pH value of the
aqueous solution [25].
Fig. 1 Schematic drawing of the LPC process and the electrostatic deposition
process in aqueous suspension
2.2 Consolidation via LAM
LMD is conducted on a three-axis handling system
(Schuler-Held) equipped with a diode laser system (Laserline
LDF 2000-30) emitting at wavelengths of 1025 and 1064 nm.
Using a special optical setup a focal spot diameter of approx.
0.6 mm is generated. The powderis injected via a coaxial
powder feed nozzle (Fraunhofer ILT) and a disc-based
feeding system (GTV Verschleißschutz PF2/2) using Ar gas.
Argon is fed through the beam path for additional shielding
from the surrounding atmosphere.
Bulk samples were produced using a laser power of 370 W,
a deposition speed of 2,000 mm/min and a powder feed rate of
1.3 g/min on a water-cooled plate to ensure rapid heat transfer
to the substrate. A two directional deposition pattern,
maintaining constant track offset of 350 μm and height offset
of 210 μm, is used to manufacture bulk samples with 40
layers.
Fig. 2 Schematic drawing of LMD (left) and SLM (right)
SLM is conducted on a laboratory SLM machine (Aconity
MIDI) equipped with a 1kW fiber laser (IPG YLR-1000-WC-
Y14) emitting a wavelength of 1070 nm. The laser scanner is
used to generate a focal spot diameter of approx. 80 μm.
Cubic bulk samples (5 mm3) were manufactured using a
chess-like pattern with a constant layer height of 30 μm, a
scanning speed of 800 mm/s and a laser power of 160 W.
2.3 Microstructural characterization
Microstructural characterization is conducted using light
optical microscopy (LOM) after standard metallographic
preparation of cross sections perpendicular to building
direction and etching with “Nital” agent (3 Vol.% HNO3
(aq.)). Additionally the samples are examined using a
scanning electron microscope (Zeiss Leo 1455EP) in SE-
mode.
2.4 Mechanical characterization
For mechanical characterization quasistatic compression
tests with constant speed (vc=0.0833 mm/min) at room
temperature and at 600°C were performed. A servohydraulic
testing system (Schenck PC63M, Instron 8800 controller)
with a 63kN load cell, equipped with a high temperature
furnace (MTS 653) was used to test cylindrical water-jet cut
specimens (diameter 4 mm, height 5-6 mm). Lubrication
agent (Molykote) was used to minimize friction between the
specimens and the compression dies.
198 Markus B. Wilms et al. / Procedia CIRP 74 (2018) 196–200
Author name /Procedia CIRP 00 (2018) 000–000 3
3. Results
The laser processing (dispersion) of colloidal aqueous
suspension of Y2O3nanoparticles resulted in a significant
reduction of the agglomerates (Fig. 3).
Figures 3a-c) show the presence of agglomerated Y2O3
nanoparticles in dependence of the used treatment method as
imaged by SEM.While ultrasonication of the suspension
already leads to deagglomeration, dispersion by means of
LPC evidently leads to less agglomerates.
Fig.3 Deagglomeration of Y2O3nanoparticles by different treatment methods.
(a-c) SEM images. (D) UV-Vis extinction spectra. (E) Measurement of the
fraction of Y2O3nanoparticles with hydrodynamic diameters >100nm by
dynamic light scattering.
This conclusion is also supported by UV-Vis extinction
spectroscopy (Fig. 3d)) where the extinction is increased by a
better dispersion of the nanoparticles (at the same
concentration). Fig. 3e shows the fraction of particles larger
than 100 nm for different dispersion methods as extracted
from dynamic light scattering measurements. This method
which is dominated by large scatting entities additionally
supports the above observation, i.e.,only laser dispersion by
LPC leads to a significant reduction of the agglomerates.
The subsequent adsorption of laser-irradiated nanoparticles on
raw steel powder, which is also performed in aqueous
suspension, resultsin homogeneous distribution of
nanoparticles on the steel raw powders surface (Fig. 4).
Fig.4 SEM image of raw steel powder (a) and decorated steel powder with
0.3wt% Y2O3(b)
The nanoparticle deposition is achieved by
dielectrophoretic interaction between nanoparticle and
micropowder. For the suspension apH of 6is adjusted
leading to negatively charged steel powder particles and
positively charged nanoparticles. After deposition the
suspension is dried in a furnace (50°C) for several hours. The
steel powder does not additionally oxidize during its transient
immersion time in water as confirmed by REM-EDX
analysis.
The manufactured powder composites are processed with
LMD with the setup described in 2.2. In contrast to non-
reinforced steel powder the melt pool during processing
becomes more turbulent, which is also indicated by increased
spark formation. However, specimens with porosities of
approx. 0.5% could be manufactured and no further
adjustments of process parameters had to be performed. No
cracks could be observed in the manufactured specimens. The
microstructure is characterized by large elongated grains,
which exceed the distance between interlayer boundaries and
therefore indicate epitaxial grain growth (Fig. 5). The grains
are oriented in building direction with asubtle inclination of a
few degrees caused the curvature of the solidification front in
combination with the used building strategy.Grain refinement
by heterogeneous nucleation on dispersed nanoparticles is not
observed. This may be related to the poor wettability of
yttrium oxide by iron-chromium melts. Vickers hardness
measurements (HV10) further confirm that (within the error
of the measurement) the distributed nano-scaled oxides have
no influence on hardness of the material (data not shown).
Fig.5 Light optical microscope image (a) of the microstructure of LMD
produced sample,(b)SEM image revealing the presence of homogenously
distributed oxide particles
A more critical test for ODS steels are compression tests at
high temperatures, since these materials are typically used in
high-temperature environments. The performed compression
tests reveal decreasing mechanical strength with increasing
testing temperature, which is expected and typical for steels.
However, the mechanical properties of steel, reinforced with
nano-scaled Y2O3(labelled in Fig. 6as “Y2O3”), are superior
compared to the unreinforced material. Whereas the increase
of compression stress at room temperature for reinforced steel
is rather small, the increase at higher testing temperatures
(600°C) becomes significantly more pronounced, which can
be explained by impairment of climb or glide motion of
dislocations by dispersed nanoparticles.
Fig.6 Averaged compression behavior at room temperature (a) and 600°C (b)
Markus B. Wilms et al. / Procedia CIRP 74 (2018) 196–200 199
4Author name /Procedia CIRP 00 (2018) 000000
To test the SLM-processability of the powder composites,
further specimens are built by SLM (Fig. 7). These specimens
exhibit porosities of approx. 0.8%. The microstructure is
characterized by elongated grains in building direction. The
width of these grains is considerably smaller than the grains
observed in LMD specimens, which may be caused by the
utility of a smaller beam diameter and therefore higher
solidification rates. Additionally, no inclination of the growth
direction of the grains is visible. However, epitaxial grain
growth can be observed.
Fig. 7 Photograph of the SLM specimen on a316L substrate material (a),
SEM image of homogenously distributed oxides in SLM built specimen (b)
A large number of “spotsindicate the presence of sub-100
nm-sized dispersoids(Fig. 7 right). These small populations
of dispersoids cannot be resolved by the resolution of the used
SEM system. Detailed analysis of these areasrequire
transmission electron microscopy but are not within the scope
of this study.
4. Conclusions and Outlook
The feasibility of a novel powder synthesis route,
consisting of LPC and subsequent electrophoretic deposition
is demonstrated in this study. Powder composites, which are
characterized by ahomogenous distribution of Y2O3-
nanoparticles on the surface of micrometer-sized stainless
steel particles, could be synthesized.The powder composites
were successfully processed by the two LAM processes of
LMD and SLM, leading to bulk specimens with low
porosities and homogenous distribution of nanoscale
dispersoids. Compression tests at elevated temperatures
demonstrate the superior performance of reinforced material
compared to raw stainless steel specimens.
Future investigations will focus on the mechanical
characterization of the SLM processed material as well as the
microstructural characterization by TEM. In order to qualify
these materials for industrial application further mechanical
tests such as long-term creep tests and evaluation of high
energy neutron resistance need to be performed.
Acknowledgments
We thank Veronica Rocio Molina Ramirez for conducting
SEM analysis and Mareen Goßling for her contribution in
performing SLM experiments.
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energy dose.Sci Rep, 2017, 7, 1316
... An approach utilizing laser-processed powder material containing the metallic and ceramic components of the alloy as a feedstock also has been demonstrated. [25][26][27][28] For the LAM process of directed energy deposition (DED), also referred to as laser metal deposition (LMD), general feasibility has been demonstrated using mechanically alloyed powder material [29][30][31]. However, pronounced agglomeration and clustering of oxide nanoparticles in DED-manufactured material are observed [32,33], resulting in the dispersion of agglomerated oxide dispersoids with reduced number densities compared to L-PBF processed material. ...
... [38] HSLC offers higher solidification rates of up to 10 6 K/s [39] compared to conventional DED processes with approx. 10 4 K/s [27,40] and therefore is considered to significantly reduce agglomeration tendencies of nano-scaled oxides during the melting stage, frequently observed in DED processed PM2000 material [25][26][27][28][29]. ...
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In this work, we demonstrate the feasibility of manufacturing an iron-based oxide-dispersion-strengthened (ODS) PM2000 composite material with the chemical composition of Fe20Cr4.5Al0.5Ti + 0.5Y 2 O 3 (in wt.%) via the advanced directed energy deposition (DED) process of high-speed laser cladding (HSLC). The characteristic high solidification rates of HSLC processes allow the successful dispersion of nano-scaled yttrium-based oxides in the ferritic stainless steel matrix. The effective suppression of nano-particle agglomeration during the melting stage, which is frequently observed in conventional DED processes of ODS materials, is reflected by smaller dispersoid sizes and corresponding higher hardness of manufactured specimen compared to DED-manufactured counterparts.
... It can be seen that the grain size of the as-printed IN718/Y 2 O 3 composite sample is slightly larger than that of the as-printed monolithic IN718 sample. The limited grain refinement effect in the as-printed IN718/Y 2 O 3 composite sample is the result of the low wettability between the Y 2 O 3 nanoparticles and the IN718 matrix, which makes them not effective as nucleation sites [35] . However, after solutionizing and aging, there is an increase in equiaxed grains formation in the Y 2 O 3 -reinforced sample after heat treatment as shown in Figure 7C and D. Due to this, the average grain size of the Y 2 O 3 -reinforced sample decreases from 19.1 ± 3.1 (before heat treatment) to 17.1 ± 7.2 µm (after solutionizing) to 12.5 ± 4.1 µm (after aging). ...
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A metal matrix composite with Inconel 718 as the base metal and yttrium oxide (Y2O3) as the reinforcement particles was fabricated by the laser powder bed fusion technology. This paper presents a comprehensive study on the influence of the Y2O3 reinforcement particles on the microstructures and mechanical properties of the heat-treated printed composite. Complex precipitates formation between the Y2O3 nanoparticles and the carbonitride precipitates were shown. The complex precipitates separated into individual Y2O3 and titanium nitride (TiN) nanoparticles after heat treatment. Nano-sized Y-Ti-O precipitates were observed after solutionization due to the release of supersaturated Y in the metal matrix. Grain refinement was also observed in the heat-treated composites due to the high number of nano-sized precipitates. After solutionizing and aging, the grain size of the Y2O3-reinforced sample is 28.2% and 33.9% smaller, respectively, than that of the monolithic Inconel 718 sample. This effectively reduced the segregation of Nbat the grain boundaries and thus, γ′ and γ′′ precipitates were distributed in the metal matrix more homogeneously. Combined with the increased Orowan strengthening from a significantly higher number of nano-sized precipitates and grain boundary strengthening, the composite achieved higher yield strength, and ultimate tensile strength (1099.3 MPa and 1385.5 MPa, respectively) than those of the monolithic Inconel 718 (1015.5 MPa and 1284.3 MPa, respectively).
... Accordingly, crack-tolerant matrix materials, such as aluminum [206,437], aluminum-silicon based alloys [205,207,[438][439][440], and austenitic steels, e.g., 304L [315,441,442] and 316L [357,367,412,[443][444][445][446], can be used to produce defect-free oxide-reinforced parts. High strength ferritic ODS steels, such as PM2000 [13,325,[447][448][449][450], MA956 [451], 18Cr-2W-0.5Ti-0.3Y 2 O 3 [79] and 14Cr-1W-0.3Mn-0.3Si-0.2Ni-0.3TiH 2 -0.3Y 2 O 3 [452] exhibit higher crack susceptibilities, increasing the probability for crack formation during manufacturing, which is frequently observed in PM2000 material. [447,448] However, effective dispersion on nano-scaled oxide particles (Fig. 16a-c), typically enriched in Y and O (Fig. 16d-j) is achieved in PBF-processed ODS alloys. ...
Article
Oxide dispersion strengthened (ODS) alloys are characterized by nanoscale oxide particles homogeneously dispersed in a metallic matrix. They have been developed driven by technological applications such as gas turbines that require increased material strength and creep properties at elevated temperatures, as well as increased resistance to high-energy neutron atmospheres as needed in modern nuclear reactors. Additive manufacturing (AM) offers the possibility to sustainably shorten the conventional sinter-based process chain of ODS materials and is additionally capable of the direct production of complex components. This work aims to critically review the current state of additive manufacturing of ODS alloys, which is mainly based on singular studies and the deduction of influence factors. Challenges in production are emphasized such as the production of suitable powder materials and consolidation techniques including in-situ manufacturing techniques. A main emphasis of this review are process-related influences on the final ODS material and its microstructural features as well as mechanical performance. Different classes of ODS alloys are presented and discussed along with their fields of use. Current drawbacks of ODS alloys are highlighted, enabling a focused development required for the widespread application of this class of materials.
... These suitable additives are hypothesized to improve the properties of the primary alloy. The modified feedstock can be procured [8,9] by (1) simple mixing of additive and primary alloy powders [43] (2) deposition/coating of additive on the surface of the primary alloy powders [44,45] (3) mechanical alloying like ball milling of additive and primary alloy powders [9,36,[46][47][48][49][50] (4) gas atomization of primary alloy powders along with additive [51]. The additive size and quantity of the additive and feedstock procurement method can influence of the final properties of feedstock modified alloy. ...
Article
Feedstock modified powders were produced by ball-milling commercial 316 L stainless steel powder and 1 wt.% additive (Cerium oxide–CeO2, lanthanum (III) nitrate hexahydrate–La(NO3)3.6H2O and chromium nitride–CrN). Laser-powder bed fusion (L-PBF) was performed on modified feedstock using 180, 200, and 220 W laser power. The influence of additives on microstructure and corrosion performance was investigated on the as-printed and ground/polished conditions of L-PBF-316L-additive. The corrosion performance was dependent on the type of the additives. The microstructure of the alloys was correlated with the observed corrosion behavior.
... The modified feedstock powders are sometimes called metal matrix composites (MMCs). The MFP can be procured by: a. producing a prealloyed powder as a combination of starting powders and additive via mechanical alloying [179,[249][250][251][252][253][254][255][256][257] b. coating the starting powder with additive [258][259][260] c. simple mixing of starting powder and additive [261]. Several researchers had successfully printed AM components using modified 316L feedstock. ...
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The applications of laser-powder bed fusion (LPBF), an emerging additive manufacturing (AM) technique, are rapidly growing in various industries. The superior and consistent mechanical and corrosion properties of LPBF-printed components are essential for engineering applications. The 316L stainless steel (SS) is an essential alloy with widespread applications from household items to nuclear and aerospace industries. Extensive research is conducted to understand and improve the mechanical properties of LPBF printed 316L SS. Studying the corrosion behavior of LPBF printed 316L has attracted only limited attention. Additionally, a discrepancy in the corrosion performance of LPBF printed 316L has been reported due to the complex microstructure and defects introduced during LPBF. Therefore, understanding the influence of processing parameters and feedstock on defects and microstructure becomes critical in understanding the processing-corrosion relationships and producing LPBF printed 316L components with reproducible properties. This review presents the influence of feedstock, processing parameters, and post-processing techniques on manufacturing defects, microstructure, and corrosion performance of LPBF printed 316L. Strategies and hypotheses to improve the corrosion resistance of LPBF printed 316L are also presented.
... 74, No. 9, 2022 https://doi.org/10.1007/s11837-022-05418-6 Ó 2022 The Author(s) blending, [21][22][23] along with methods to deposit oxides onto powders in situ, have been reported as alternative feedstock techniques for fabrication by AM. [24][25][26][27][28] While some promising results have been reported, challenges related to heterogeneity and agglomeration of pre-existing Y 2 O 3 remain, and these approaches typically depend on MA processing, which can be a limiting factor to scalability. Several recent studies have sought to bypass the MA step and leverage oxidation within the melt pool, observing the formation of nano-scale oxides from trace amounts of deoxidizers with favorable free energies, such as Si and Mn in austenitic steel, especially at low partial pressures of oxygen in the LPBF chamber. ...
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Laser powder bed fusion (LPBF) additive manufacturing (AM) is a promising route for the fabrication of oxide dispersion strengthened (ODS) steels. In this study, 14YWT ferritic steel powders were produced by gas atomization reaction synthesis (GARS). The rapid solidification resulted in the formation of stable, Y-containing intermetallic Y 2 Fe 17 on the interior of the powder and a stable Cr-rich oxide surface. The GARS powders were consolidated with LPBF. Process parameter maps identified a stable process window resulting in a relative density of 99.8%. Transmission electron microscopy and high-energy x-ray diffraction demonstrated that during LPBF, the stable phases in the powder dissociated in the liquid melt pool and reacted to form a high density (1.7 × 10 ²⁰ /m ³ ) of homogeneously distributed Ti 2 Y 2 O 7 pyrochlore dispersoids ranging from 17 to 57 nm. The use of GARS powder bypasses the mechanical alloying step typically required to produce ODS feedstock. Preliminary mechanical tests demonstrated an ultimate tensile and yield strength of 474 MPa and 312 MPa, respectively.
... These suitable additives are hypothesized to improve the properties of the primary alloy. The modified feedstock can be procured [8,9] by (1) simple mixing of additive and primary alloy powders [43] (2) deposition/coating of additive on the surface of the primary alloy powders [44,45] (3) mechanical alloying like ball milling of additive and primary alloy powders [9,36,[46][47][48][49][50] (4) gas atomization of primary alloy powders along with additive [51]. The additive size and quantity of the additive and feedstock procurement method can influence of the final properties of feedstock modified alloy. ...
Article
Additive manufacturing (AM) is an emerging technology that can build 3d-component in a single step via the layer-by-layer process. Selective laser melting (SLM) is a popular powder bed fusion (PBF) – AM technique that involves rapid heating and cooling cycles with broad temperature gradients and complex thermal history. Moreover, the SLM components are often reported to have lower build densification due to stochastic porosity. The complex thermal cycles and stochastic porosity can negatively influence the corrosion performance of SLM printed 316L Stainless steel (SLM-316L) alloys. The corrosion performance of SLM-316L can be improved by optimizing the SLM processing parameters to improve the density and/or performing post-processing. However, post-processing increases the cost and time to deliver the components and is desired to avoid. Therefore, modifying the feedstock to increase corrosion resistance and therefore tolerance of the pores would help streamline the workflow and eliminate expensive post-manufacturing steps. In this research, the feedstock modification was conducted using ball milling of various additives and 316L powder. Corrosion performance of the SLM specimen was dependent on the additive used to modify the feedstock. Some of the additives imparted significantly improved corrosion performance, as evident from the high pitting and repassivation potentials and absence of metastable pitting. Observed corrosion performance was correlated with the microstructure which was studied using scanning and transmission electron microscopes. X-ray photoelectron spectroscopy and time of flight secondary ion mass spectrometry was used to study the surface film. Role of additives on microstructure and corrosion performance will be discussed.
... Y 2 O 3 [112] or 1 wt./wt% CrN [113]) or deposition or coating of an additive on its surface (for example, 0.3 wt./wt% nano-sized Y 2 O 3 deposited on the surface of a ferritic stainless steel powder [114]). In these reports, very few properties of the composite powder have been presented and there are no comparisons between those properties and those of the starting powder counterpart. ...
Article
Alloys containing a dispersion of fine, stable oxides can develop useful creep strength to 90 percent of their melting temperature, providing a capability of 100 to 150°C or more over conventional high-temperature alloys. Such oxide dispersion-strengthened alloys allow other alloying additions to be optimized to provide superior oxidation resistance. Activities to develop such alloys for severe high-temperature applications are described, together with opportunities for further understanding of the development and growth of protective oxide scales of chromia and alumina. In particular, the use of oxides such as ThO2 and Y2O3 as dispersd phases resulted in the generation of important observations of the ‘reactive element effect’ in high-temperature oxidation. By analogy to the separation of the requirements for alloy strengthening and environmental resistance by insertion of a dispersion of oxide particles, examples are provided of other issues that can be addressed by various dispersed phases, without compromising existing alloy properties.
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The effects of the modification of a high‐γ' Ni‐8.5Cr‐5.5Al‐1Ti (wt.%) model superalloy with 0.5 wt.% Y2O3, manufactured by laser powder‐bed fusion, on the microstructure and compressive creep resistance were investigated. Compared to the base alloy, the oxide‐dispersion strengthened (ODS) alloy exhibits 8‐10 times slower creep rates at 800 °C, over a wide range of compressive stresses (35‐250 MPa). Two creep regimes were observed: diffusional creep, hypothesized to be due to grain boundary sliding, and dislocation creep, with stress exponents n=2 and n=5, respectively. A creep‐resistance anisotropy was observed. Compared to the horizontal direction, the vertical build direction is characterized by lower creep rates, due to the vertically elongated grain structure. Nonetheless, the ODS alloy’s weakest (horizontal) direction shows better creep resistance than the non‐ODS alloy in its strongest (vertical) direction, despite a higher number of as‐built defects (slag, cracks) in the ODS alloy. The strengthening potential of ODS modification of additively manufactured nickel‐based superalloys is thus demonstrated. The development of a successful commercial ODS nickel superalloy for additive manufacturing processing however requires further additions of grain‐boundary strengthening elements as the oxide dispersoids did not significantly increase the grain‐boundary strength, since grain boundary cracking was still prevalent in the ODS alloy. This article is protected by copyright. All rights reserved.
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Highly active, structurally disordered CoFe2O4/CoO electrocatalysts are synthesized by pulsed laser fragmentation in liquid (PLFL) of a commercial CoFe2O4 powder dispersed in water. A partial transformation of the CoFe2O4 educt to CoO is observed and proposed to be a thermal decomposition process induced by the picosecond pulsed laser irradiation. The overpotential in the OER in aqueous alkaline media at 10 mA cm⁻² is reduced by 23% compared to the educt down to 0.32 V with a Tafel slope of 71 mV dec⁻¹. Importantly, the catalytic activity is systematically adjustable by the number of PLFL treatment cycles. The occurrence of thermal melting and decomposition during one PLFL cycle is verified by modelling the laser beam energy distribution within the irradiated colloid volume and comparing the by single particles absorbed part to threshold energies. Thermal decomposition leads to a massive reduction in particle size and crystal transformations towards crystalline CoO and amorphous CoFe2O4. Subsequently, thermal melting forms multi-phase spherical and network-like particles. Additionally, Fe-based layered double hydroxides at higher process cycle repetitions emerge as a byproduct. The results show that PLFL is a promising method that allows modification of the structural order in oxides and thus access to catalytically interesting materials.
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This study investigated the feasibility of using HfO2 as a dispersoid in the additive manufacturing process, compared to Y2O3. The effect of pre-annealing treatment was investigated too. Scanning electron microscopy (SEM) analyses revealed unusually coarse deposition layers for both the HfO2 and Y2O3 dispersed oxide dispersion strengthed (ODS) steels, in both the as-milled and the pre-annealed conditions. The deposited layer of the HfO2 dispersed ODS steel had relatively coarser grains than the deposited layer of the Y2O3 dispersed ODS steel in both the as-milled and the pre-annealed conditions. Moreover, the SEM results also revealed the presence of nanometer sized particles in all the deposition layers of both Y2O3 and HfO2 dispersed ODS steels, and their number densities were far lower than those in conventional bulk ODS steels. However, transmission electron microscopy analyses revealed that the dispersion and retention of nanoparticles within the melt were not achieved, even with HfO2 as a dispersoid, in contrast to the results from the SEM analyses. Furthermore, the deposition layers of both the as-milled Y2O3 and HfO2 ODS steels also exhibited an unusual nano-grained structure. The microhardnesses of the HfO2 and the Y2O3 dispersed ODS steels in both the as-milled and the pre-annealed conditions were higher than the substrate. Furthermore, the Y2O3 dispersed ODS steel had a higher microhardness than the HfO2 dispersed ODS steel in both the as-milled and the pre-annealed conditions.
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Pulsed laser melting in liquid (PLML) has emerged as a facile approach to synthesize submicron spheres (SMSs) for various applications. Typically lasers with long pulse durations in the nanosecond regime are used. However, recent findings show that during melting the energy absorbed by the particle will be dissipated promptly after laser-matter interaction following the temperature decrease within tens of nanoseconds and hence limiting the efficiency of longer pulse widths. Here, the feasibility to utilize a picosecond laser to synthesize Ge SMSs (200~1000 nm in diameter) is demonstrated by irradiating polydisperse Ge powders in water and isopropanol. Through analyzing the educt size dependent SMSs formation mechanism, we find that Ge powders (200~1000 nm) are directly transformed into SMSs during PLML via reshaping, while comparatively larger powders (1000~2000 nm) are split into daughter SMSs via liquid droplet bisection. Furthermore, the contribution of powders larger than 2000 nm and smaller than 200 nm to form SMSs is discussed. This work shows that compared to nanosecond lasers, picosecond lasers are also suitable to produce SMSs if the pulse duration is longer than the material electron-phonon coupling period to allow thermal relaxation.
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div class="title">Mechanisms of Particle Coarsening and Phase Transformation in Oxide Dispersion Strengthened Steels During Friction Stir Welding - Volume 22 Issue S3 - Keith E. Knipling, Bradford W. Baker, Daniel K. Schreiber
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We present a novel route for the adsorption of pulsed laser-dispersed nanoparticles onto metal powders in aqueous solution without using any binders or surfactants. By electrostatic interaction, we deposit Y2O3 nanoparticles onto iron-chromium based powders and obtain a high dispersion of nano-sized particles on the metallic powders. Within the additively manufactured component, we show that the particle spacing of the oxide inclusion can be adjusted by the initial mass fraction of the adsorbed Y2O3 particles on the micropowder. Thus, our procedure constitutes a robust route for additive manufacturing of oxide dispersion-strengthened alloys via oxide nanoparticles supported on steel micropowders.
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A study of creep mechanisms of ferritic ODS alloys was based on high temperature tensile/compression tests combined with electron microscopy analysis of deformed specimens and in situ observations of dislocation motion under stress. The ¯ow stress, its strain-rate sensitivity and its temperature dependence were discussed in terms of solid solution hardening, mutual dislocation interaction, the Orowan process, a thermally activated detachment model and solute drag effects. The mechanisms controlling the ¯ow stress of ferritic ODS alloys were identi®ed. # 2002 Published by Elsevier Science B.V.
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Pulsed laser ablation of pressed yttrium-ion-garnet powders in water is studied and compared to the ablation of a single crystal target. We find that target porosity is a crucial factor which has far-reaching implications on nanoparticle productivity. Although nanoparticle size distributions obtained by analytical disc centrifugation and transmission electron microscopy (TEM) are in agreement, X-ray diffraction and energy dispersive X-ray analysis show that only nanoparticles obtained from targets with densities close to that of a bulk target lead to comparable properties. Our findings also show why the gravimetrical measurement of nanoparticle productivity is often flawed and needs to be complemented by colloidal productivity measurements. The synthesized YIG nanoparticles are further reduced in size by laser fragmentation to obtain sizes smaller 3 nm. Since the particle diameters are close to the YIG lattice constant, these ultrasmall nanoparticles reveal an immense change of the magnetic properties exhibiting huge coercivity (0.11 T) and irreversibility fields (8 T) at low temperatures.
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Oxide dispersion strengthened (ODS) alloys exhibit superior mechanical and physical properties due to the presence of nanoscopic Y(Al, Ti) oxide precipitates, but their manufacturing process is complex. The present study is aimed at further investigation of the application of an alternative, Additive Manufacturing (AM) technique, Selective Laser Melting (SLM), to the production of consolidated ODS alloy components. Mechanically alloyed PM2000 (ODS-FeCrAl) powders have been consolidated and a fine dispersion of Y-containing precipitates were observed in an as built thin-walled component, but these particles were typically poly-crystalline and contained a variety of elements including O, Al, Ti, Cr and Fe. Application of post-build heat treatments resulted in the modification of particle structures and compositions; in the annealed condition most precipitates were transformed to single crystal yttrium aluminium oxides. During the annealing treatment, precipitate distributions homogenised and localised variations in number density were diminished. The resulting volume fractions of those precipitates were 25-40% lower than have been reported in conventionally processed PM2000, which was attributed to Y-rich slag-like surface features and inclusions formed during SLM.
Article
A dual-phase 12Cr oxide-dispersion-strengthened (ODS) alloy, with improved corrosion and oxidation resistance exhibits promising void swelling resistance and microstructural stability under Fe 2þ ion irradiation to 800 dpa at 475 C. Dispersoids were originally present in both ferrite and tempered martensite grains, with the latter having a wider range of dispersoid sizes. In both phases dispersoids >10 nm in diameter are incoherent with the matrix, while smaller dispersoids are coherent. During irradiation the larger incoherent dispersoids shrank and disappeared. Beyond 60 dpa dispersoids in both phases approached a near-identical equilibrium size of ~2e2.5 nm, which appears to be rather independent of local displacement rate. Grain morphology was found to be stable under irradiation. Compared to other ferritic-martensitic alloys, the ion-induced swelling of this alloy is quite low, arising from swelling resistance associated with both tempered martensite and dispersoids in both phase. Swelling in tempered martensite is an order of magnitude less than in the ferrite phase.