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@PHDTHESIS{Schmitt:1047598,
      author       = {Schmitt, Johannes-Christian},
      title        = {{B}ewertung lokaler {E}igenspannungsverteilungen bei der
                      lokalen {B}auteilreparatur durch {K}altgasspritzen},
      volume       = {680},
      school       = {Bochum},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2025-04401},
      isbn         = {978-3-95806-861-2},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {154, xxvii},
      year         = {2025},
      note         = {Dissertation, Bochum, 2025},
      abstract     = {In recent years, there has been a notable increase in
                      interest in cold spraying, largely due to its potential
                      applications in repair and additive manufacturing.
                      Nevertheless, further research is required to gain insight
                      into the residual stress state and mechanical integrity of
                      cold sprayed coatings. This thesis is concerned with the
                      repair of Inconel 718 components. Such components are
                      employed in gas turbines and other applications due to their
                      exemplary material properties. In this context, a cavity was
                      created, based on the typical repair process, with a depth
                      of 4 mm and 60° conical walls, as a result of the milling
                      process, for the purpose of crack removal. The filling of
                      such deep cavities with Inconel 718 results in the formation
                      of a dense coating with good adhesion. A comprehensive
                      residual stress analysis of the entire cavity was conducted
                      using neutron diffraction, with near-surface measurements
                      supplemented by the incremental hole-drilling method. The
                      resulting residual stress state was found to be
                      direction-dependent due to the geometric limitations of the
                      cavity, as expected, but the specific gas conditions showed
                      the anticipated results. Further experiments were conducted
                      to investigate the effects of different robot speeds by in
                      situ curvature measurements using the ICP sensor. Based on
                      the findings, an analytical model was developed to estimate
                      the resulting temperature gradient at the gas spot. These
                      findings are supported by particle diagnostics and data from
                      an implemented, three-dimensional CFD model in ANSYS Fluent.
                      The results were also used to vary the resulting spray spot
                      of different nozzle geometries in the context of additive
                      manufacturing and to discuss the resulting residual stresses
                      in conjunction with the data pertaining to the gas and
                      particles. The results demonstrate that the restoration of
                      Inconel 718 components by means of cold spraying results in
                      the formation of dense repair coatings with good mechanical
                      properties. The residual stress state is anisotropic,
                      depending on the geometric limitations. In general, it is
                      possible to systematically adjust the residual stress state
                      in cold sprayed coatings by modifying the process parameters
                      and the nozzle geometry in order to achieve the desired
                      stress state. The present work was carried out within the
                      framework of the DFG project VA163/11-1.},
      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-2025-04401},
      url          = {https://juser.fz-juelich.de/record/1047598},
}