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@PHDTHESIS{Duan:830192,
      author       = {Duan, Ran},
      title        = {{P}rediction of {O}xidation {I}nduced {L}ife {T}ime for
                      {FCC} {M}aterials at {H}igh {T}emperature {O}peration},
      volume       = {374},
      school       = {RWTH Aachen},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliotek},
      reportid     = {FZJ-2017-03768},
      isbn         = {978-3-95806-230-6},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {vi, 180 S.},
      year         = {2017},
      note         = {RWTH Aachen, Diss., 2016},
      abstract     = {With an increasing application of high temperature alloys,
                      especially Ni-based superalloys in automobile and other
                      industrial fields, the ability to predict components‟
                      lifetime becomes a predominant demand from both safety and
                      energy consumption aspects. In the present investigation, an
                      attempt was made to develop a generalized oxidation lifetime
                      model for chromia-forming FCC alloys that can be
                      incorporated into alloy data sheets and easily understood
                      and employed by component designers. The model captures the
                      most important damaging oxidation effects relevant for
                      component design: wall thickness loss, scale spallation and
                      the occurrence of “breakaway” oxidation. The material
                      used for development of the concept was the wrought NiCrW
                      base alloy 230. For deriving modeling input parameters and
                      for verification of the model approach, specimens of this
                      alloy with different thicknesses were exposed cyclically for
                      different times at temperatures in the range 950 - 1050°C
                      in static laboratory air. The studies concentrated on thin
                      specimens (thickness 0.2 - 0.5 mm) to obtain data for
                      critical subscale depletion processes resulting in
                      “breakaway” oxidation within reasonably achievable test
                      times up to 3000 h. The oxidation kinetics and oxidation
                      induced subscale microstructural changes from the long term
                      tests were combined with results from thermogravimetric
                      analyses (TGA), scanning electron microscopy (SEM) with
                      energy dispersive x-ray (EDX) spectroscopy and electron
                      backscatter diffraction (EBSD), as well as glow discharge
                      optical emission spectroscopy (GDOES). Oxidation induced
                      microstructural changes as function of specimen thickness,
                      time and temperature were estimated and modeled using the
                      software packages Thermocalc and DICTRA. The modeling of the
                      oxide scale spalling and re-formation was based on the
                      cyclic oxidation spallation program (COSP), which was
                      published previously. The program was modified to adapt the
                      approach to the present experimental observations. A new
                      model was developed to describe accelerated oxidation
                      occurring after longer exposure times in case of the
                      thinnest specimens. The calculated oxidation kinetics was
                      correlated with the Cr reservoir equation, by means of which
                      the relation between the consumption and the remained
                      concentration of the scale forming element (Cr) in the
                      alloys is established as a function of temperature and
                      specimen thickness. The results obtained by the reservoir
                      approach were compared with calculations of Cr concentration
                      profiles using a finite difference model. Based on this
                      approach, a generalized lifetime diagram is proposed in
                      which wall thickness loss as function of time, specimen
                      thickness and temperature as well as times to reaching a
                      critical chromium subscale depletion are presented. The same
                      approach was subsequently applied to the nickel base alloys
                      X and NiCr 8020 as well as the austenitic steel Nicrofer
                      2020. Both Ni base alloys showed shorter times to critical
                      subscale depletion than alloy 230; alloy X mainly due to
                      higher scale growth rates, alloy NiCr 8020 due to poorer
                      scale adherence and a lower initial Cr content. The
                      austenitic steel showed the shortest lifetime mainly due to
                      Mn and Ti induced high growth rates of the chromia scale and
                      resulting low Cr interface concentrations.},
      cin          = {IEK-2},
      cid          = {I:(DE-Juel1)IEK-2-20101013},
      pnm          = {899 - ohne Topic (POF3-899)},
      pid          = {G:(DE-HGF)POF3-899},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:0001-2017071203},
      url          = {https://juser.fz-juelich.de/record/830192},
}