Cr concentration dependence of overestimation of long term creep life in strength enhanced high Cr ferritic steels

K. Maruyama, H. Ghassemi Armaki, R. P. Chen, K. Yoshimi, M. Yoshizawa, M. Igarashi

Research output: Contribution to journalArticlepeer-review

33 Citations (Scopus)

Abstract

Creep rupture data and microstructural degradation during aging of high Cr ferritic boiler steels with enhanced creep strength have been studied with special attention to prediction of long term creep rupture life. Tempered lath martensite structure in the high Cr ferritic steels remains unchanged during short term aging, whereas static recovery of the lath martensite structure proceeds when diffusion distance during aging becomes sufficiently long as is the case in long term creep. The static recovery brings about premature failure in long term creep and decreases in apparent activation energy for creep life. The decrease in activation energy is responsible for overestimation of rupture life reported in strength enhanced high Cr ferritic steels. The boundary from a short term region with high activation energy QH to a long term region with low activation energy QL moves towards longer time with decreasing Cr concentration. The difference in activation energy (QH - QL) primarily determines the extent of overestimation of rupture life predicted from short term data. In general, the extent of overestimation is less serious at 9%Cr as compared to 12%Cr.

Original languageEnglish
Pages (from-to)276-281
Number of pages6
JournalInternational Journal of Pressure Vessels and Piping
Volume87
Issue number6
DOIs
Publication statusPublished - 2010 Jun

Keywords

  • Activation energy for rupture life
  • High Cr ferritic steel
  • Microstructural degradation
  • Overestimation of rupture life
  • Tempered lath martensite

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering

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