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@PHDTHESIS{Lttschwager:17293,
      author       = {Lüttschwager, Frank},
      title        = {{R}auchgasseitige {K}orrosion von {N}ickelbasislegierungen
                      für zukünftige {D}ampfkraftwerke},
      volume       = {132},
      school       = {RWTH Aachen},
      type         = {Dr. (Univ.)},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {PreJuSER-17293},
      isbn         = {978-3-89336-773-3},
      series       = {Schriften des Forschungszentrums Jülich : Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {145 S.},
      year         = {2011},
      note         = {Record converted from JUWEL: 18.07.2013; RWTH Aachen,
                      Diss., 2011},
      abstract     = {Coal is still the most important energy source in Germany.
                      In 2009 it produced 42.9 $\%$ of the overall German
                      electrical power. Coal is available world-wide in large
                      quantities and can be delivered economically. One of the
                      possible ways to reduce CO$_{2}$ pollution is the increase
                      of efficiency of coal fired power plants, which requires
                      steam conditions of up to 700 °C – 730 °C and 350 bar.
                      Because many German power units will reach the end of their
                      technical lifespan in a few years or the following decade,
                      one will have the possibility to build up modern types of
                      power plants with increased efficiency of more than 50 \%.
                      Some international standards (European Pressure Equipment
                      Directive or ASME Boiler and Pressure Vessel Code) require
                      100 000 hour creep rupture strength of 100 MPa at 750 °C.
                      Therefore, nickel base alloys are in the focus of material
                      qualification processes. Nickel base alloys are well
                      investigated due to their hot corrosion behaviour. It is
                      known that sodium sulphate may generate hot corrosion on
                      those alloys at temperatures above its melting point of 884
                      °C. On nickel base alloys an eutectic mixture of nickel
                      sulphate and sodium sulphate with a melting point of 671 °C
                      can be generated, which leads to accelerated corrosion. This
                      work examines, whether the high amount of sulphur and alkali
                      metals will induce hot corrosion at the estimated working
                      temperature on devices manufactured from nickel base alloy.
                      Two synthetic coal ash deposits, according to the chemical
                      composition of hard coal and lignite, and typical flue gases
                      with and without sulphur dioxide were blended of pure
                      agents. The reactions of the deposits with heater tubes´
                      materials and synthetic flue gases are examined in the
                      temperature range from 650 °C to 800 °C and different time
                      ranges up to 2000 hours. The corroded specimen are examined
                      with SEM/EDX to identify relevant corrosion products and
                      determine the corrosivity of deposited compounds. Deposits
                      increase the corrosion rate of nickel base alloys in
                      comparison to air oxidation, even when there is no gaseous
                      sulphur oxide, like SO$_{2}$ or SO$_{3}$. This effect may be
                      found by examining model systems, for example inert deposits
                      like metal oxides, silicates or aluminosilicates and
                      corrosive deposits like alkali sulphates. Kinetic
                      investigations are carried out with a newly developed
                      electrochemical pickling method, which allows to calculate
                      the rates of hot corrosion underneath deposits. A material
                      ranking is given for the alloys 263, 617 and 740, and it can
                      be shown that under coal firing conditions lignite ash is
                      much more corrosive than hard coal ash. Finally,
                      thermodynamical calculations show possible reaction products
                      formed during the combustion of various world market coals
                      in power units. The coals’ potential of corrosion attacks
                      is evaluated qualitatively by using experimental and
                      thermodynamical data.},
      cin          = {IEK-2},
      ddc          = {500},
      cid          = {I:(DE-Juel1)IEK-2-20101013},
      pnm          = {Rationelle Energieumwandlung},
      pid          = {G:(DE-Juel1)FUEK402},
      typ          = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
      url          = {https://juser.fz-juelich.de/record/17293},
}