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@PHDTHESIS{Igel:1043291,
      author       = {Igel, Jens},
      title        = {{I}nnovative {P}lasma {S}prayed {T}hermal {B}arrier
                      {C}oatings for {E}nhanced {F}lexibility in {G}as {T}urbine
                      {O}peration},
      volume       = {665},
      school       = {Bochum},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2025-02817},
      isbn         = {978-3-95806-827-8},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {V, 153, XXXVI},
      year         = {2025},
      note         = {Dissertation, Bochum, 2025},
      abstract     = {Thermal barrier coatings (TBCs) in power plant turbines are
                      primarily designed for high thermal insulation properties.
                      As a result, they enable a high combustion temperature in
                      the turbine, making the power generation process very
                      efficient. In the future, however, the operational
                      flexibility of modern power plant turbines will become
                      increasingly important to maintain grid stability. Frequent
                      fluctuations in the amount of electricity fed into the grid
                      due to the high volatility of renewable energy sources, as
                      well as changing loads, require constant adjustment of power
                      generation. In the future, this will be made possible by gas
                      turbines that must be started up and shut down quickly and
                      flexibly. The challenges for the coating system arise from
                      the different properties of the materials applied. The
                      different expansion of layers and substrates during
                      temperature changes introduces stresses into the coating
                      system when the turbine is started up or shut down. In
                      addition, the high operating temperatures lead to
                      detrimental phase transformations and sintering of the
                      ceramic top layer, reducing the strain tolerance and thus
                      the flexible application of the coatings. The objective of
                      this study was therefore to develop an optimized TBC system
                      capable of withstanding rapid mechanical load and
                      temperature changes. The development focused on the
                      optimization of the bond coat as well as the top layer of
                      the TBC system. For the bond coat optimization, aspects such
                      as surface roughness, thermal expansion coefficients and the
                      effect of pre-oxidation of the bond coat on the performance
                      of the coatings during thermal cycling were investigated. In
                      contrast, the effect of different microstructures produced
                      by different plasma spraying processes on the thermal
                      cycling performance of the ceramic topcoats was
                      investigated. In addition, innovative analysis methods were
                      used for the various plasma-sprayed thermal barrier coatings
                      to investigate coating properties and failure mechanisms in
                      detail. These methods include digital image correlation,
                      which enables to analyze strain changes on the sample
                      surface during thermal cycling. In this way, the forced
                      elongation of the ceramic top layer by the substrate
                      material could be shown, as well as local changes in
                      elongation over the cycles, which finally might result in
                      coating failure. A further method is the laser shock
                      adhesion test. This allows to determine the interfacial
                      bonding of coatings and to introduce specific defects into
                      coating systems. The growth of these defects can be observed
                      during thermal cycling, providing important insights for
                      investigating the failure mechanisms in thermal barrier
                      coating systems. Overall, the optimizations more than
                      doubled the service life of the thermal barrier coatings
                      compared to a reference coating system as used in today’s
                      turbines. In addition, insights were gained into the failure
                      mechanisms that occur with differently structured
                      topcoatings. At the end of the work, further opportunities
                      for improvement were identified that can be investigated in
                      the future.},
      cin          = {IMD-2},
      cid          = {I:(DE-Juel1)IMD-2-20101013},
      pnm          = {1241 - Gas turbines (POF4-124)},
      pid          = {G:(DE-HGF)POF4-1241},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      doi          = {10.34734/FZJ-2025-02817},
      url          = {https://juser.fz-juelich.de/record/1043291},
}