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@PHDTHESIS{Koch:826737,
author = {Koch, Denise Silke},
title = {{E}ntwicklung selbstheilender {W}ärmedämmschichten},
volume = {355},
school = {Universität Bochum},
type = {Dr.},
address = {Jülich},
publisher = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
reportid = {FZJ-2017-00955},
isbn = {978-3-95806-201-6},
series = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
Umwelt / Energy $\&$ Environment},
pages = {X, 120 S.},
year = {2016},
note = {Universität Bochum, Diss., 2016},
abstract = {The presented work is dealing with the manufacturing of
self-healing thermal barrier coatings by atmospheric plasma
spraying that are applicable in high temperature processes
with thermal loading. The turbine blades of gas turbines for
example, experience thermal stresses that are induced into
the thermal barrier coatings and can cause crack
development. After a certain time these cracks grow and lead
to a spallation of the coating. By this, the turbine blade
would not be protected any more. With the integration of a
self-healing process, the time between maintenances can be
extended to save operational costs. The basic idea to
realize such self-healing coatings is the integration of
MoSi$_{2}$ as self-healing particles. The oxidation of
MoSi$_{2}$ leads to the formation of SiO$_{2}$ that can
infiltrate cracks and seals them. This can prevent the
spallation of the coating. The presented work was performed
within a project named SAMBA (self-healing thermal barrier
coatings) that was funded by the European Union. The first
step in the production of a self-healing thermal barrier
coating was the integration of MoSi$_{2}$ particles into a
coating. Yttria stabilized zirconia (YSZ) was used as
coating matrix since this is the state of the art material.
Due to a decomposition of the MoSi$_{2}$ when spraying it at
conditions that are needed to produce coatings made out of
YSZ, the manufacturing of a homogeneous mixed coating of YSZ
and MoSi$_{2}$ from a powder mixture of both materials was
not possible. This problem was solved by using a second
injection point located at a distance from the
plasma-torch-exit. Nevertheless the coatings made out of YSZ
and pure MoSi$_{2}$ were not suitable to work as a
self-healing thermal barrier coating due to the fact that
the oxidation of MoSi$_{2}$ was not controlled. The volume
expansion caused by the formation of SiO$_{2}$ induces
stresses into the coating that lead to a failure and the
spallation of the coating. The second step in the
development was to encapsulate the MoSi$_{2}$ particles with
Al$_{2}$O$_{3}$, as this encapsulation was supposed to work
as a protection against a premature oxidation of the
MoSi$_{2}$. As the spraying process leads to a deformation
of the particles during deposition on the substrate, a
pre-encapsulation of the powder would be destroyed. Because
of this, the encapsulation has to be formed in-situ within
the coating. Several coatings were produced using Al doped
MoSi$_{2}$ to integrate it into the YSZ coatings. These
coatings were heat treated and by this several requirements
were determined that need to be fulfilled in order to enable
the self-healing process. Coatings that have been produced
using spraying parameters, that enable the fulfillment of
these requirements, and these coatings resulted in an
improvement of the lifetime of the coatings compared to
standard YSZ coatings. Within the SAMBA project further
analysis and investigations will be performed to be able to
judge on the self-healing abilities of coatings produced by
the procedures described in this work.},
cin = {IEK-1},
cid = {I:(DE-Juel1)IEK-1-20101013},
pnm = {113 - Methods and Concepts for Material Development
(POF3-113) / HITEC - Helmholtz Interdisciplinary Doctoral
Training in Energy and Climate Research (HITEC)
(HITEC-20170406)},
pid = {G:(DE-HGF)POF3-113 / G:(DE-Juel1)HITEC-20170406},
typ = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
url = {https://juser.fz-juelich.de/record/826737},
}