Citation: Calignano, F.; Manfredi, D.;
Marola, S.; Lombardi, M.; Iuliano, L.
Production of Dense Cu-10Sn Part by
Laser Powder Bed Fusion with Low
Surface Roughness and High
Dimensional Accuracy. Materials
2022, 15, 3352. https://doi.org/
10.3390/ma15093352
Academic Editors: Ludwig Cardon
and Clemens Holzer
Received: 9 April 2022
Accepted: 5 May 2022
Published: 7 May 2022
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Article
Production of Dense Cu-10Sn Part by Laser Powder Bed Fusion
with Low Surface Roughness and High Dimensional Accuracy
Flaviana Calignano
1,2
, Diego Manfredi
2,3,4,
* , Silvia Marola
4
, Mariangela Lombardi
2,3
and Luca Iuliano
1,2
1
Department of Management and Production Engineering (DIGEP), Politecnico di Torino, Corso Duca Degli
Abruzzi, 24, 10129 Torino, Italy; flaviana.calignano@polito.it (F.C.); luca.iuliano@polito.it (L.I.)
2
Integrated Additive Manufacturing Center (IAM)—Politecnico di Torino, Corso Castelfidardo, 51,
10129 Torino, Italy; mariangela.lombardi@polito.it
3
Department of Applied Science and Technology (DISAT), Politecnico di Torino, Corso Duca Degli Abruzzi, 24,
10129 Torino, Italy
4
Center for Sustainable Future Technologies, Istituto Italiano di Tecnologia (IIT), Via Livorno 60,
10144 Torino, Italy; silvia.marola@iit.it
* Correspondence: diego.manfredi@polito.it
Abstract:
Tin-bronze alloys with a tin content of at least 10 wt% have excellent mechanical properties,
wear resistance, and corrosion resistance. Among these alloys, Cu-10Sn was investigated in this
study for production with the laser powder bed fusion process with a 500W Yb:YAG laser. In
particular, a design of experiment (DoE) was developed in order to identify the optimal process
parameters to obtain full density, low surface roughness, and high dimensional accuracy. Samples
were characterized with Archimedes’ method and optical microscopy to determine their final density.
It was shown that the first method is fast but not as reliable as the second one. A first mechanical
characterization was performed through microhardness tests. Finally, a set of process parameters
was identified to produce fully dense samples with low surface roughness and high accuracy. The
results showed that the volumetric energy density could represent an approach that is too simplified,
therefore limiting the direct correlation with the physical aspects of the process.
Keywords:
tin-bronze alloys; laser powder bed fusion; Archimedes’ density; optical microscopy;
surface roughness; volumetric energy density
1. Introduction
The continuous evolution of additive manufacturing (AM) processes for metals is
continuing to attract increasing attention from sectors in which there is the widespread use
of copper alloys. Among the additive technologies, the laser powder bed fusion (L-PBF)
process, also known as selective laser melting (SLM), mainly attracts the attention of the
sectors that need a dense product with a good dimensional accuracy of the components [
1
].
The high reflectivity of Cu at the wavelength of the lasers commonly used in the majority of
L-PBF commercial systems, combined with its high thermal conductivity, causes a certain
instability in the process, as well as the risk of damaging the optical mirror of the L-PBF
machine due to the sustained copper back-reflections [
2
]. For this reason, although there
are new studies on lasers with different wavelengths, many researchers have investigated
the use of copper alloys with lower optical reflectivity than pure copper. Considering the
literature on materials, although constant research is being conducted for the development
of new high-performance copper alloys for the L-PBF process [
3
–
7
], bronze, one of the
oldest metal alloys known to mankind, is still widely used in many industrial applications.
The fields of application range from works of art with bronze sculptures and musical
instruments, to applications of technological importance such as electrical connectors and
high precision springs. Furthermore, bronze, thanks to its excellent resistance to salt-water
Materials 2022, 15, 3352. https://doi.org/10.3390/ma15093352 https://www.mdpi.com/journal/materials
