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@PHDTHESIS{Mutter:826748,
      author       = {Mutter, Markus Gerhard},
      title        = {{H}erstellung thermisch gespritzter {S}chichten mit
                      optimierten {S}pannungseigenschaften},
      volume       = {354},
      school       = {Universität Bochum},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2017-00966},
      isbn         = {978-3-95806-200-9},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {198 S.},
      year         = {2016},
      note         = {Universität Bochum, Diss., 2016},
      abstract     = {Gasturbines are widely used in stationary applications for
                      power generation as well as in aero applications due to
                      their high efficiency. The use of ceramic thermal barrier
                      coatings (TBC) on the thermally high loaded turbine
                      components allows either to increase the gas inlet
                      temperature and therefore the efficiency of the system or to
                      increase the lifetime of the system while maintaining the
                      gas inlet temperature on it´s initial level. The ceramic
                      thermal barrier coatings are typically deposited by
                      atmospheric plasma spraying (APS) or electron beam –
                      physical vapor deposition (EB-PVD). While the latter leads
                      to microstructures with beneficial strain tolerance, the APS
                      scores with it´s high deposition rates and the lower
                      thermal conductivity due to the lamellar structure of these
                      coatings perpendicular to the loading direction. Several
                      factors occur during high temperature operation of the
                      gasturbines that can increase the stiffness of the thermal
                      barrier coating, influence the stresses within the thermal
                      barrier coating, and finally may lead to delamination of the
                      coating. The residual stress state of the as-sprayed coating
                      can have an important effect on the behavior of the coating
                      in operation. The in situ measurement of the sample´s
                      curvature during the atmospheric plasma spraying process
                      allows the evaluation of the residual stress evolution
                      during the process and the determination of the residual
                      stress depth profiles in the as-sprayed coatings. However,
                      determination of the change of the stress depth profile in
                      operation is not possible by this technique. The incremental
                      hole-drilling method on the other hand is a widely used
                      technique to determine residual stress depth profiles in the
                      near surface region of components. By a comparison of the
                      two measurement techniques for as-sprayed coatings the
                      enhancement of the incremental hole-drilling method on
                      coating systems is aspired. This finally enables the
                      determination of the change of the residual stress states
                      within the coating, the substrate and especially at the
                      interface between the coating and the substrate by the
                      thermo-mechanical loadings occuring in operation. A
                      fundamental understanding of the interaction between the
                      coating microstructure and the stress evolution is required
                      to enable specific fabrication of coatings with well defined
                      residual stress states. The investigation of these
                      interrelations is aim of the present work. For this purpose,
                      the different particle conditions in the plasma plume were
                      evaluated in this work. Therefore, measurements of the
                      temperature and velocity of single particles along the
                      plasma plume were performed and combined with a simulation
                      of the particle trajectories and the heat transfer between
                      plasma and particles. Experimental studies of single splats
                      deposited on mirror-polished substrates showed a high
                      variety of splat morphologies that were classified into four
                      basic splat-types to allow a systematic evaluation. The
                      formation of these splat-types was linked to distinct
                      particle and substrate conditions. The introduced particle
                      melting degrees enabled the quantification of the relative
                      fractions of the different particle conditions and,
                      consequently, the relative fractions of the splat-types
                      based on the particle temperature measurements. The
                      formation of the coating and the connected properties was
                      interpreted as the statistical distribution of the impact of
                      single particles with various conditions. It was further
                      shown that the properties of the deposited coating exhibit a
                      distinct correlation to the distributions of the particle
                      conditions. This is in particular the case for the coating
                      porosity, which influences the Young´s modulus and the
                      stress evolution. While the Young´s modulus of the coating
                      is well defined by the porosity and the bonding between the
                      single splats, the stress evolution exhibits more complex
                      relations. The stress evolution in a single splat is
                      dominated by the occurrence of various plastic effects
                      (stress relaxation factors) depending on statistical
                      factors, and therefore an exact prediction is hardly
                      possible. An exemplary description was conducted based on
                      existing analytical models and own finite element and
                      analytical calculations. The layering of the single splats
                      during the coating formation process was interpreted in the
                      context of the statistic distribution of the different
                      splat-types. However, it was not possible to completely
                      describe the stress evolution by the influencing parameters
                      used in this investigation. Since the impact frequency of
                      the splats showed an effect on the stress evolution, the
                      influence of the interface temperature between the single
                      splats during deposition on the stress relaxation factors is
                      supposed to play a key role. The outcome of this work can be
                      used as starting point for the fabrication of atmospheric
                      plasma sprayed coatings with well defined residual stress
                      states. This offers the possibility to optimize the residual
                      stress states in terms of the operation conditions as well
                      as the fabrication of suitable samples for the enhancement
                      of the incremental hole-drilling method on coating systems.},
      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/826748},
}