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Creep modeling for life evaluation and strengthening mechanism of tungsten alloyed 9–12% Cr steels

  • Kyu-Seop Park
  • Dong-Sik Bae
  • Sung -Keun Lee
  • Goo -Hyun Lee
  • Jung -Ho Kim
  • Takao Endo
Article

Abstract

Recently, high strength tungsten (W) alloyed steels have been developed for use in power plants with higher steam conditions for environmental reasons as well as the improvement of thermal efficiency resulting in lower fuel costs. In order to establish a creep modeling of high strength martensitic steel and to understand the basic role of W in tungsten alloyed 9–12Cr steels, conventional martensitic steels (X20CrMoV121, X20CrMoWV121, and Mod9Cr-1Mo) and tungsten alloyed steels (NF616 and HCM12A) were employed for creep tests and creep behavior analyses by the Ω method. The proposed creep model, which takes into account both primary and tertiary creep, satisfactorily described the creep curves and accurately predicted creep life, as martensitic steel undergoes a relatively large amount of primary creep, up to nearly 30%, over its normal life. The tungsten alloyed steels exhibited a smaller minimum creep rate and a larger stress exponent compared to the conventional steels. In addition, in tungsten alloyed steel, the Ω value features strong stress dependence such that creep life is prolonged at lower stresses due to high Ω values. The importance of the Ω value from the standpoint of creep strengthening in primary and tertiary creep is discussed.

Keywords

creep life omega method imaginary initial strain rate stress exponent 

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Copyright information

© Springer 2006

Authors and Affiliations

  • Kyu-Seop Park
    • 1
  • Dong-Sik Bae
    • 1
  • Sung -Keun Lee
    • 2
  • Goo -Hyun Lee
    • 3
  • Jung -Ho Kim
    • 4
  • Takao Endo
    • 5
  1. 1.Department of Ceramic Science and EngineeringChangwon National UniversityGyeongnamKorea
  2. 2.Department of Materials Science and EngineeringDong-A UniversityBusanKorea
  3. 3.Korea Institute of Machinery and MaterialsGyeongnamKorea
  4. 4.Korea Photonics Technology InstituteGwangjuKorea
  5. 5.Department of Materials EngineeringYokohama National UniversityJapan

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