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@ARTICLE{Klein:848311,
      author       = {Klein, Felix and Wegener, Tobias and Litnovsky, Andrey and
                      Rasinski, Marcin and Tan, Xiaoyue and Schmitz, Janina and
                      Linsmeier, Christian and Coenen, Jan Willem and Du, Hongchu
                      and Mayer, Joachim and Breuer, Uwe},
      title        = {{O}n {O}xidation {R}esistance {M}echanisms at 1273 {K} of
                      {T}ungsten-{B}ased {A}lloys {C}ontaining {C}hromium and
                      {Y}ttria},
      journal      = {Metals},
      volume       = {8},
      number       = {7},
      issn         = {2075-4701},
      address      = {Basel},
      publisher    = {MDPI},
      reportid     = {FZJ-2018-03556},
      pages        = {488 -},
      year         = {2018},
      abstract     = {Tungsten (W) is currently deemed the main candidate for the
                      plasma-facing armor material of the first wall of future
                      fusion reactors, such as DEMO. Advantages of W include a
                      high melting point, high thermal conductivity, low tritium
                      retention, and low erosion yield. However, was an accident
                      to occur, air ingress into the vacuum vessel could occur and
                      the temperature of the first wall could reach 1200K to 1450K
                      due to nuclear decay heat. In the absence of cooling, the
                      temperature remains in that range for several weeks. At
                      these temperatures, the radioactive tungsten oxidizes and
                      then volatilizes. Smart W alloys are therefore being
                      developed. Smart alloys are supposed to preserve properties
                      of W during plasma operation while suppressing tungsten
                      oxide formation in case of an accident. This study focuses
                      on investigations of thin film smart alloys produced by
                      magnetron sputtering. These alloys provide an idealistic
                      system with a homogeneous distribution of the elements W,
                      chromium (Cr), and yttrium (Y) on an atomic scale. The
                      recommended composition is W with 12 weight $\%$ of Cr and
                      0.5 weight $\%$ of Y. Passivation and a suppression of WO3
                      sublimation is shown. For the first time, the mechanisms
                      yielding the improved oxidation resistance are analyzed in
                      detail. A protective Cr2O3 layer forms at the surface. The
                      different stages of the oxidation processes up to the
                      failure of the protective function are analyzed for the
                      first time. Using 18O as a tracer, it is shown for the first
                      time that the oxide growth occurs at the surface of the
                      protective oxide. The Cr is continuously replenished from
                      the bulk of the sample, including the Cr-rich phase which
                      forms during exposure at 1273K. A homogenous distribution of
                      yttria within the W-matrix, which is preserved during
                      oxidation, is a peculiarity of the analyzed alloy. Further,
                      an Y-enriched nucleation site is found at the interface
                      between metal and oxide. This nucleation sites are deemed to
                      be crucial for the improved oxidation resistance.},
      cin          = {IEK-4 / ER-C-2 / ZEA-3},
      ddc          = {530},
      cid          = {I:(DE-Juel1)IEK-4-20101013 / I:(DE-Juel1)ER-C-2-20170209 /
                      I:(DE-Juel1)ZEA-3-20090406},
      pnm          = {143 - Controlling Configuration-Based Phenomena (POF3-143)},
      pid          = {G:(DE-HGF)POF3-143},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000445096800018},
      doi          = {10.3390/met8070488},
      url          = {https://juser.fz-juelich.de/record/848311},
}