Article
Vat Photopolymerization of Cemented Carbide Specimen
Thomas Rieger
1,2,
* , Tim Schubert
1
, Julian Schurr
1
, Andreas Kopp
1
, Michael Schwenkel
1
, Dirk Sellmer
3
,
Alexander Wolff
4
, Juliane Meese-Marktscheffel
4
, Timo Bernthaler
1
and Gerhard Schneider
1
Citation: Rieger, T.; Schubert, T.;
Schurr, J.; Kopp, A.; Schwenkel, M.;
Sellmer, D.; Wolff, A.; Meese-
Marktscheffel, J.; Bernthaler, T.;
Schneider, G. Vat Photopolymerization
of Cemented Carbide Specimen.
Materials 2021, 14, 7631. https://
doi.org/10.3390/ma14247631
Academic Editors: Antonino Recca,
Ludwig Cardon and Clemens Holzer
Received: 22 November 2021
Accepted: 7 December 2021
Published: 11 December 2021
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4.0/).
1
Materials Research Institute, Faculty Mechanical Engineering and Materials Science, Aalen University,
73430 Aalen, Germany; Tim.Schubert@hs-aalen.de (T.S.); Julian.Schurr@hs-aalen.de (J.S.);
Andreas.Kopp@hs-aalen.de (A.K.); Michael.Schwenkel@hs-aalen.de (M.S.);
Timo.Bernthaler@hs-aalen.de (T.B.); Gerhard.Schneider@hs-aalen.de (G.S.)
2
Department of Mechanical Engineering, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
3
MAPAL Precision Tool Dr. Kress KG, 73431 Aalen, Germany; Dirk.Sellmer@mapal.com
4
H.C. Starck Tungsten GmbH, 38642 Goslar, Germany; Alexander.Wolff@hcstarck.com (A.W.);
Julia.Meese-Marktscheffel@hcstarck.com (J.M.-M.)
* Correspondence: Thomas.Rieger@hs-aalen.de; Tel.: +49-7361-576-1630
Abstract:
Numerous studies show that vat photopolymerization enables near-net-shape printing of
ceramics and plastics with complex geometries. In this study, vat photopolymerization was investi-
gated for cemented carbide specimens. Custom-developed photosensitive WC-12 Co (wt%) slurries
were used for printing green bodies. The samples were examined for defects using quantitative
microstructure analysis. A thermogravimetric analysis was performed to develop a debinding pro-
gram for the green bodies. After sintering, the microstructure and surface roughness were evaluated.
As mechanical parameters, Vickers hardness and Palmqvist fracture toughness were considered. A
linear shrinkage of 26–27% was determined. The remaining porosity fraction was 9.0%. No free
graphite formation, and almost no
η
-phase formation occurred. WC grain growth was observed.
76% of the WC grains measured were in the suitable size range for metal cutting tool applications.
A hardness of 1157 HV10 and a Palmqvist fracture toughness of 12
MPa
√
m
was achieved. The
achieved microstructure exhibits a high porosity fraction and local cracks. As a result, vat pho-
topolymerization can become an alternative forming method for cemented carbide components if the
amount of residual porosity and defects can be reduced.
Keywords:
cemented carbide; additive manufacturing; vat photopolymerization; characterization;
heat treatment
1. Introduction
Cemented carbides are mainly used in the manufacturing industry for cutting, grind-
ing, and drilling applications. These materials are characterized by high strength and
wear resistance, especially at high temperatures and in corrosive environments [
1
]. A
variety of material properties can be achieved through a defined fraction of fine refractory
carbides in a ductile metallic matrix [
2
]. Using tungsten carbide (WC) (the hard material
phase) and cobalt (Co) (the metallic binder phase) is the preferred material system that
combines high strength with high fracture toughness [
3
]. Tools made of cemented carbides
are usually manufactured through pressing and extrusion with subsequent sintering [
4
].
Also, metal powder injection molding (MIM) can be used to manufacture cemented carbide
components [
5
]. Pressing and the MIM process require a specific and expensive tool for
each individual component, which makes the manufacturing of small batches only rarely
economically attractive. Post-processing has limited applicability and is expensive for
cemented carbide components. Additive manufacturing (AM) is a fast, cost-effective, and
resource-saving method for the customized production of small batches and components
with complex geometries. Unused material can be reused for printing new components [
6
].
New tool designs can be realized based on the layer by layer technology. Inner cooling
Materials 2021, 14, 7631. https://doi.org/10.3390/ma14247631 https://www.mdpi.com/journal/materials
