Evaluation of long-term creep rupture life of strength enhanced high Cr ferritic steel on the basis of its temperature dependence

K. Maruyama, Junya Nakamura, Kyosuke Yoshimi

Research output: Contribution to conferencePaper

3 Citations (Scopus)

Abstract

Conventional time-temperature-parameter (TTP) methods often overestimate long-term creep rupture life of creep strength enhanced high Cr ferritic steels. The cause of the overestimation is studied on the basis of creep rupture data analysis on Gr.91, 92 and 122 steels. There are four regions with different values of stress exponent n for creep rupture life commonly in stress-rupture data of the three ferritic steels. Activation energies Q for rupture life in the regions take at least three different values. The values of n and Q decrease in a longer-term region. The decrease in Q value is the cause of the overestimation of long-term rupture life predicted by the conventional TTP methods neglecting the change in Q value. Therefore, before applying a TTP method creep rupture data should be divided into several data sets so that Q value is unique in each divided data set. When this multi-region analysis is adopted, all the data points of the steels can be described accurately, and their long-term creep life can be evaluated correctly. Substantial heat-to-heat and grade-to-grade variation in their creep strength is suggested under recent service conditions of USC power boilers.

Original languageEnglish
Pages732-743
Number of pages12
Publication statusPublished - 2014 Jan 1
Event7th International Conference on Advances in Materials Technology for Fossil Power Plants - Waikoloa, HI, United States
Duration: 2013 Oct 222013 Oct 25

Other

Other7th International Conference on Advances in Materials Technology for Fossil Power Plants
CountryUnited States
CityWaikoloa, HI
Period13/10/2213/10/25

Keywords

  • Breakdown of creep strength
  • Creep life prediction
  • Multi-region analysis
  • Power boiler steel
  • Time-temperature-parameter method

ASJC Scopus subject areas

  • Fuel Technology
  • Renewable Energy, Sustainability and the Environment

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    Maruyama, K., Nakamura, J., & Yoshimi, K. (2014). Evaluation of long-term creep rupture life of strength enhanced high Cr ferritic steel on the basis of its temperature dependence. 732-743. Paper presented at 7th International Conference on Advances in Materials Technology for Fossil Power Plants, Waikoloa, HI, United States.