Laser Assisted Turning of Ceramics

Institute of Mineral Engineering
Department of Ceramics and Refractory Materials
Univ.-Prof. Dr. rer. nat. R. Telle
Mechanical Materials Behaviour
Laser Assisted Turning Of Ceramics
The industrially feasable processing methods for the machining of sintered ceramic materials up to now
are restricted to processing methods with a geometrically undefined edge (grinding, honing, lapping)
which are characterized by low abrasion rates and insufficient flexibility. The method of laser assisted
turning which is still in the development phase provides new perspectives in respect of machining time
and geometrical complexity through use of a geometrically defined cutting tool.
In laser assisted turning a rotating workpiece is
continually heated by a laser in front of the cut-
amount. Ceramics with low laser absorption
properties are doted with coloring additives which
ting tool. The aim is to achieve a partial heating
restricted to the shear- or deformation zone directly in front of the tool contact (Fig. 1).
exhibit no negative influence on the material
properties.
The developed ceramics are tested at the Fraunhofer Institute for Production Technology (IPT)
regarding their suitability for laser assisted turning (Fig. 2).
Fig. 1: Principle of laser assisted turning
Due to the viscous-elastic behavior of the grain
border phase the material is locally weakened and
thus shearable at high temperatures. At the Institute of Mineral Engineering appropriate glass
phase systems being developed with softening
points at ~1000°C. Additionally the microstructure is optimized for this method in regard to
the grain-size distribution and glass-phase-
Fig. 2: Prototype at the Fraunhofer IPT
Up to now two oxidic materials – Al2O3 and ZrO2
– and two non-oxidic materials – LPS-SiC and
Si3N4 – have been tested for suitability in laser
assisted turning. Especially Zircon has displayed
outstanding results regarding surface quality (Fig.
3).
protective layer
surface
for preparartion
Fig. 4: Rim zone of a laser assisted turned ZrO2-ceramic
Fig. 3: SEM picture of a ZrO2 surface after laser assisted
turning
TEM analysis provides evidence that this method
of machining does not induce larger defects in the
rim-zone (Fig.4).
Apart from shearing of whole grains occurrence
of trans-crystalline fractures is evident. Grain
debris is detected on the surface to different extends, depending on the material group. The resealing of occurring fractures during the turning
process by the viscous glass phase was observed
in experiments with optimized processing parameters.
Results show that the plastic behavior of ceramic materials under machining conditions results in interesting opportunities for innovative machining methods utilizing the high energy- and force insertion to acquire an excellent surface quality without triggering strength reducing fractures. The continuing research
in this project will - apart from investigations regarding the strength of materials after laser assisted turning -include economic studies of this method.
This work with the project number 12 915 N was financed by the Arbeitsgemeinschaft industrieller Forschungsvereinigungen
(AIF) by founds of the Federal Ministry for Economic Affairs and Energie.
Institute of Mineral Engineering
Department of Ceramics and Refractory Materials
Please contact:
Mauerstrasse 5, 52064 Aachen
phone: +49-(0)241-8094968
fax:
+49-(0)241-8092226
www.ghi.rwth-aachen.de
Univ.-Prof. Dr. rer. nat. R. Telle
phone: +49-(0)241- 8094968
fax:
+49-(0)241-8092226
e-mail: [email protected]