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11thInternationalConferenceonthe
ScienceofHardMaterials
ICSHM11
KhaoLak,Thailand,25‐29March2019
ProgramandExtendedAbstracts
FILAMENT-EXTRUSION 3D PRINTING OF
HARDMETAL AND CERMET PARTS
Walter Lengauer1,*, Ivica Duretek2, Markus Fürst1, Joamin Gonzalez-Gutierrez2, Stephan Schuschnigg2
Christian Kukla3
1 Vienna University of Technology, Getreidemarkt 9/164CT, 1060 Vienna, Austria
2 Montanuniversität Leoben, Dept. of Polymer Engineering Science, Otto-Glöckel-Str. 2, 8700 Leoben,
Austria
3 Montanuniversität Leoben, Industrial Liaison Dept., Peter-Tunner-Str. 27, 8700 Leoben, Austria
* Corresponding author: walter.lengauer@tuwien.ac.at
ABSTRACT
Additive manufacturing is fast-growing and a most interesting fabrication technology also for parts prepared
out of composite materials. We recently reported on the first ever conducted extrusion-printing techniques on
WC-Co-based hardmetals and Ti(C,N)-based cermets [1,2]. While both materials were prepared with
multiphase starting mixtures blended in an in-house drum milling procedure, the present work reports a study
using two commercially available starting powders (RTP powders) used for fused-filament fabrication (FFF)
of composite parts. In addition, the parts of the present study have a more complicated geometry, not
accessible to pressing and MIM techniques.
The hardmetal and cermet powders contained paraffin wax, since they are normally used for press-and-sinter
applications, their weight was 7 and 3 kg, respectively. As the specific density of the cermet is approx. half of
that of the hardmetal both batches were similar in volume. The multicomponent binder system for FFF was
developed at the Chair of Polymer Processing of Montanuniversität Leoben. Feedstocks of various powder
contents between 42 and 52 vol% were established.
Filaments were prepared using a single screw extruder. An extrusion die with a diameter of 1.75 mm and a
length on 20 mm was used. After exiting the die, the extrudate was transported in a Teflon conveyor belt.
Finally, the filament was spooled using a self-developed haul-off and winding unit. The filaments’ diameter
and ovality was monitored by a laser-based measuring device. A constant geometry of the filament is
important for its continuous transportation in an FFF machine. For this reason, the diameter and the ovality of
the produced filament were monitored during production. The ovality is the difference between the diameter
measure in the horizontal direction minus the diameter measured in the vertical direction; thus, if the filament
has a perfectly round cross-section, the ovality is zero. Table 1 gives the diameter and ovality of both types of
filaments. Both types of filaments were within the recommended tolerances of 1.75 ± 0.15 mm.
Tab. 1: Diameter and ovality of the two types of filaments
Material
Average
Diameter (mm)
Ovality
(mm)
Hardmetal filament
1.759 ± 0.0234
0.014 ± 0.0026
Cermet filament
1.724 ± 0.0314
0.010 ± 0.0023
Printing trials were performed on a Wanhao Duplicator i3V2. The nozzle diameter was 0.4 and 0.6 mm and a
layer height between 0.1 and 0.38 mm, depending on the part size. The slicer software Slic3r Prusa edition
used was. The extrusion temperature was 250 °C and the bed temperature 80 °C. The printing surface was the
standard printing surface of the Wanhao FFF machine.
In all printed parts the first layer had a good adhesion to the printing bed (Figure 1). The layer in contact with
the printing bed had a smoother and continuous surface, compared to the next layers. The printed layers were
bonded correctly.
77
Fig. 1: FFF printed part on the printing bed, left: hard metal, right: cermet
Solvent debinding was performed on a plastic grid in cyclohexane at 60°C using a magnetic stirrer. The parts
were typically submerged for 48-72h, depending on the maximum wall thickness of the parts. After drying
and weighing the parts were subjected to a tube furnace for debinding the backbone and pre-sintering. Flowing
H2 and N2 atmospheres of ambient pressure and various vertex temperatures up to 800°C were applied.
After thermal debinding and weighing the parts were transferred to a vacuum sintering furnace and sintered
in a graphite crucible to final density. The sintering programs for hardmetals and cermets were different with
vertex temperatures of 1400°C and 1480°C, respectively. Figure 2 shows examples of two sintered hardmetal
parts.
Fig. 2: Sintered hardmetal parts, left: catalyst body, right: turbocharger impeller.
Examples for weight change and shrinkage data are given in Table 2, the reference being the printed body.
These figures depend on the amount of filling degree of the printing feedstock.
Tab. 2: Weight change and shrinkage of bodies of the two materials (average of 3 bodies each)
Material
Total Weight change (%)
Total Shrinkage x-y (%)
Total Shrinkage z (%)
Hardmetal
-6.83
-19.72
-22.04
Cermet
-15.03
-23.80
-26.70
References
[1] M.Kitzmantel, W.Lengauer, I.Duretek, V.Schwarz, C.Kukla, C.Lieberwirth, V.Morrison, T.Wilfinger,
E.Neubauer
Potential of extrusion-based 3D-printed hardmetal and cermet parts
Proc. WorldPM 2018, 16.-18.09.2018, Beijing (CN), Part 5, p.938-945
[2] W.Lengauer, I.Duretek, V.Schwarz, C.Kukla, M.Kitzmantel, E.Neubauer, C.Lieberwirth, V.Morrison
Preparation and properties of extrusion-based 3D-printed hardmetal and cermet parts
Proc. EuroPM 2018 (USB), 14.-18.10.2018, Bilbao (E), Session 19, Hard Metals AM
EPMA, Shrewsbury UK, ISBN: 978-1-899072-50-7
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