Degradation Mechanism of Creep Strength Enhanced Ferritic Steels for Power Plants

  • K. Sawada
  • M. Tabuchi
  • K. Kimura
Chapter

Abstract

Creep strength degradation of Creep Strength Enhanced Ferritic (CSEF) steels was investigated, focusing on microstructural degradation. The creep strength of ASME Gr.91 steel remarkably decreased in the long-term at 600oC and 650oC. If the data in the long-term are selected for regression analysis, we can accurately evaluate long-term creep strength. The data under applied stresses larger than proportional limit stress should be omitted for the analysis. Creep deformation under a stress lower than proportional limit stress is strongly affected by microstructural changes due to diffusion. After long-term creep exposure at 600oC, the martensitic lath structure was collapsed by recovery and coarsening of precipitates occurred. The recovery of lath structure preferentially occurred around prior austenite grain boundaries. The Z-phase particles nucleated around prior austenite grain boundaries during creep exposure, consuming fine MX particles that were main strengthener.

Keywords

Prior Austenite Creep Strength Proportional Limit Creep Life Lath Structure 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  • K. Sawada
    • 1
  • M. Tabuchi
    • 1
  • K. Kimura
    • 1
  1. 1.National Institute for Materials ScienceTsukubaJapan

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