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@PHDTHESIS{Letang:1055067,
      author       = {Letang, Maike},
      title        = {{E}ntwicklung von {R}eparaturmethoden für einkristalline
                      {B}auteile mittels thermischer {S}pritzverfahren},
      volume       = {692},
      school       = {Bochum},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2026-01844},
      isbn         = {978-3-95806-883-4},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {X, 211},
      year         = {2026},
      note         = {Dissertation, Bochum, 2025},
      abstract     = {Single-crystal turbine blades made of nickel-based
                      superalloys, such as CMSX-4, are of great importance for gas
                      turbines due to their excellent high-temperature properties,
                      however, they are subject to various damage mechanisms.
                      Repairing these costly components is desirable for both
                      ecological and economic reasons; however, it poses a
                      challenge as the single-crystal microstructure in the repair
                      area must be restored. This study, conducted as part of
                      Transfer Project 5 within Collaborative Research Center 103,
                      investigates the thermal spray processes Cold Gas Spraying
                      (CGS), Vacuum Plasma Spraying (VPS), and High Velocity Air
                      Fuel Spraying (HVAF), in combination with directional
                      recrystallization, as potential repair methods for
                      single-crystal CMSX- 4 turbine blades. Thermal spray
                      processes show great potential for this application due to
                      their low oxidation and high density. Differences in the
                      process conditions lead to varying coating properties. CGS
                      and VPS achieve the lowest values for porosity and oxygen.
                      HVAF coatings have the highest values for oxygen content and
                      porosity. The residual stress state of the different
                      coatings is also investigated. In the coatings that were
                      produced using CGS and HVAF, compressive residual stresses
                      can be determined, while the VPS coatings exhibit tensile
                      stresses up to a stress-free state. The analysis of the
                      adhesive tensile strength shows that HVAF coatings with the
                      highest compressive stresses fail the earliest. Directional
                      recrystallization to set a columnar microstructure of the
                      repair coatings shows clear differences in the resulting
                      microstructures, with the VPS coating having the most
                      pronounced columnar structure, while the CGS coating
                      develops predominantly equiaxed grains. The differences can
                      mainly be attributed to the different initial
                      microstructures, whereby the presence of the γ’ phase and
                      the degree of work hardening are decisive influencing
                      factors. Despite the process-related limitations of the
                      experimental setup, the fundamental feasibility of columnar
                      grain growth has been demonstrated, paving the way for
                      future optimizations with improved process control.},
      cin          = {IMD-2},
      cid          = {I:(DE-Juel1)IMD-2-20101013},
      pnm          = {899 - ohne Topic (POF4-899)},
      pid          = {G:(DE-HGF)POF4-899},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      doi          = {10.34734/FZJ-2026-01844},
      url          = {https://juser.fz-juelich.de/record/1055067},
}