% IMPORTANT: The following is UTF-8 encoded.  This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.

@PHDTHESIS{Kalfhaus:865857,
      author       = {Kalfhaus, Tobias},
      title        = {{E}ntwicklung von {R}eparaturmethoden für
                      {N}ickel-{S}uperlegierungen mittels thermischer
                      {S}pritzverfahren},
      volume       = {470},
      school       = {Univ. Bochum},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2019-05145},
      isbn         = {978-3-95806-418-8},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {VI, 126, XXX},
      year         = {2019},
      note         = {Dissertation, Univ. Bochum, 2019},
      abstract     = {The outstanding high temperature properties of Ni-based
                      superalloys are the reason for their application in modern
                      gas turbines. The development towards a singlecrystalline
                      microstructure lead to a significant increase in efficiency
                      over the past decades. Repair procedures with the potential
                      to reduce the overall cost of these expensive components are
                      of special interest for the gas-turbine industry. The
                      highquality standards and the poor weldability of Ni-based
                      superalloys limit conventional repair procedures. Thermal
                      spray techniques are a promising method for repair
                      applications due to their outstanding coating properties.
                      This thesis is engaged with the potential for a possible
                      repair application of Ni-base superalloys using vacuum
                      plasma spray (VPS) and cold gas spray (CGS). A focus of this
                      thesis is on the single crystalline repair of the alloy
                      CMSX-4. A precise measurement and control of the substrate
                      temperature during both spray techniques is important to
                      influence the microstructural properties of the coating.
                      Therefore, a heated substrate holder with a maximum
                      substrate temperature of 1000 °C was constructed and build.
                      The first part of the thesis considers the influence of an
                      increased substrate temperature on the VPS-coatings. An
                      epitaxial crystal growth of the polycrystalline repair
                      coating is observed in sections on the polished
                      single-crystalline substrate. A parameter study was used to
                      decrease the oxide content within the coatings. The specific
                      movement of the polycrystalline repair coatings into a
                      hot-zone leads to directional annealing, resulting in a
                      columnar microstructure. With the aim of stimulating grain
                      growth from the SX substrate, a FEM-thermal-field evolution
                      of a Bridgman furnace was simulated. The results indicate
                      conditions within the sample to be adequate to allow
                      hot-zone movement through a thick polycrystalline VPS-repair
                      coating originating in the SX-substrate. In the second part
                      of the thesis it is shown that the maximum gas temperature
                      of the CGS-system is not sufficient to deposit CMSX-4.
                      Therefore, the focus for CGS-repair was changed to the
                      polycrystalline repair of IN-738 using the four alloys
                      IN-625, IN-713, IN-738 and Rene’80. The residual stress of
                      the coatings is characterised using a hole-drill and a
                      curvature approach. To improve the coating thickness the
                      elastic stored energy of the coatings is reduced using the
                      heated sample holder and laser structuring results in a
                      better adhesion between the substrate and the coating.It was
                      found that subsequent HIP-heat-treatments decrease the
                      porosity with an increasing annealing temperature. The
                      strongly deformed microstructure of the CGScoatings attached
                      to aged substrate can be rejuvenated with
                      HIP-heat-treatments atoptimized annealing temperatures.
                      Simulated Stress-Strain-Curves using Indentation data
                      revealed similar strength properties of the IN-738-repair
                      coating in comparison to the IN-738-substrate.},
      cin          = {IEK-1},
      cid          = {I:(DE-Juel1)IEK-1-20101013},
      pnm          = {899 - ohne Topic (POF3-899)},
      pid          = {G:(DE-HGF)POF3-899},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/865857},
}