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@PHDTHESIS{Schlegel:283045,
      author       = {Schlegel, Nadin},
      title        = {{U}ntersuchungen zu suspensionsplasmagespritzten
                      {W}ärmedämmschichtsystemen},
      volume       = {305},
      school       = {Ruhr-Universität Bochum},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2016-01727},
      isbn         = {978-3-95806-118-7},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {X, 136 S.},
      year         = {2016},
      note         = {Keine OpenAccess Freischaltung!; Dissertation,
                      Ruhr-Universität Bochum, 2015},
      abstract     = {A higher gas inlet temperature can increase the efficiency
                      of gas turbines, that are applied in stationary power plants
                      or in planes. Therewith, the thermal stress of the turbine
                      components is increased as well, which means that all
                      turbine components need to be protected against high
                      temperature at the same time. Therefore, thermal barrier
                      coatings (TBCs) are used by means of thermal protection.
                      TBCs reduce the heat conduction to the components and thus
                      ensure that the increasing heat caused by the increased gas
                      inlet temperature does not destroy any turbine components.
                      In general, top coats are applied by the atmospheric plasma
                      spraying (APS, lamellar coatings) or by the electron
                      beam-physical vapor deposition process (EB-PVD, columnar
                      coatings). To date, the top coats still consist of yttria
                      partially-stabilized zirconia (YSZ). $\underline{In}$
                      $\underline{the}$ $\underline{first}$ $\underline{part}$
                      $\underline{of}$ $\underline{this}$ $\underline{work}$, YSZ
                      layers have been applied by suspension plasma spraying
                      (SPS). The spray parameters have been optimized, thus
                      coatings consisting of a columnar microstructure were
                      produced. Hence, the SPS process combines the advantages of
                      the APS and the EB-PVD process: high deposition rates at
                      atmospheric pressure. The behavior of the coatings under
                      cyclic temperature load has been tested. In this work, it
                      was noticed that the deposition temperature has a major
                      impact on the lifetime of the coatings in thermal cycling
                      tests. Cold deposition parameters have led to better results
                      in thermal cycling lifetime tests. However, the results have
                      been worse than those of the YSZ coatings deposited with the
                      APS process. Since the coating thicknesses of the SPS YSZ
                      coatings have been thinner than the thicknesses of the APS
                      YSZ coatings, a thin APS YSZ interlayer has been applied
                      between bond coat (BC) and SPS coating. As consequence, the
                      thermal cycling lifetime is increased. It is similar to the
                      lifetime of the APS YSZ standard coatings. However, the
                      failure mechanism of the SPS/APS double layers is different
                      to that of the APS coatings. SPS/APS double layers show a
                      significant depletion of alumina in the BC. This depletion
                      leads to the formation of ductile, fast, and bulky growing
                      oxides at the interface between BC and APS YSZ coating,
                      which lead to the failure of the coating. $\underline{In}$
                      $\underline{the}$ $\underline{second}$ $\underline{part}$
                      $\underline{of}$ $\underline{this}$ $\underline{work}$,
                      alternative materials for the application as TBC materials
                      have been tested, due to the fact that the operation
                      temperature of YSZ is limited to 1200 °C. The alternative
                      materials, which are magnesia alumina spinel,
                      Gd$_{2}$Zr$_{2}$O$_{7}$ and
                      La(Al$_{0.25}$Mg$_{0.5}$Ta$_{0.25}$)O$_{3}$ have been
                      applied by the SPS process as well. An APS YSZ interlayer
                      has been applied to all three materials. The produced
                      magnesia alumina spinel coatings show a columnar
                      microstructure. In comparison to the APS YSZ coatings, they
                      have a longer lifetime in the thermal cycling test. The
                      Gd$_{2}$Zr$_{2}$O$_{7}$ layers are segmented. A first test
                      has shown that the lifetime of these coatings are on the
                      same level as those of the APS YSZ standard coatings.
                      SPS/APS Gd$_{2}$Zr$_{2}$O$_{7}$ double layers fail in the
                      same way as the SPS/APS YSZ double layers.
                      La(Al$_{0.25}$Mg$_{0.5}$Ta$_{0.25}$)O$_{3}$ coatings show a
                      columnar microstructure. They have been tested under cyclic
                      temperature load and in the furnace test. Due to the high
                      durability of these coatings, their resistance against
                      calcium-magnesium-alumino-silicates (CMAS) has been tested
                      at elevated temperatures. The
                      La(Al$_{0.25}$Mg$_{0.5}$Ta$_{0.25}$)O$_{3}$ coatings show
                      excellent thermal cycling lifetimes under CMAS-attack, too.},
      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/283045},
}