High cycle fatigue properties of modified 9cr-1mo steel at elevated temperatures

Yoshiaki Matsumori, Jumpei Nemoto, Yuji Ichikawa, Isamu Nonaka, Hideo Miura

Research output: Chapter in Book/Report/Conference proceedingConference contribution

3 Citations (Scopus)

Abstract

Since high-cycle fatigue loads is applied to the pipes in various energy and chemical plants due to the vibration and frequent temperature change of fluid in the pipes, the highcycle fatigue behavior of the alloys used for pipes should be understood quantitatively in the structural reliability design of the pipes. The purpose of this study, therefore, is to clarify the high-cycle fatigue strength and fracture mechanism of the modified 9Cr-1Mo steel at temperatures higher than 400°C. This material is one of the effective candidates for the pipes in fast breeder demonstration reactor systems. A rotating bending fatigue test was applied to samples at 50 Hz in air. The stress waveform was sinusoidal and the stress ratio was fixed at -1. The fatigue limit was observed at room temperature and it was about 420 MPa. This value was lower than the 0.2% proof stress of this alloy by about 60 MPa. This decrease can be attributed to the cyclic softening of this material. The limited cycles at knee point was about 8×105 cycles. All fracture was initiated from a single surface crack and no inclusion-induced fracture was observed in the fracture surface by SEM. Thus, the high-cycle fatigue design based on the fatigue limit may be applicable to the modified 9Cr-1Mo steel at room temperature. The fatigue limit of about 350 MPa was also observed at 400°C, and it appeared at about 107 cycles, while it appeared at around 106 cycles at room temperature. Thus, it was confirmed that the fatigue strength of this alloy decrease with temperature. However, the fatigue limit didn't appear at 550°C up to 108 cycles. The fatigue limit may disappear in this alloy at 550°C. It is very important, therefore, to evaluate the ultra-high cycle fatigue strength of this alloy at temperatures higher than 400°C.

Original languageEnglish
Title of host publicationASME 2012 International Mechanical Engineering Congress and Exposition, IMECE 2012
Pages85-89
Number of pages5
DOIs
Publication statusPublished - 2012 Dec 1
EventASME 2012 International Mechanical Engineering Congress and Exposition, IMECE 2012 - Houston, TX, United States
Duration: 2012 Nov 92012 Nov 15

Publication series

NameASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)
Volume8

Other

OtherASME 2012 International Mechanical Engineering Congress and Exposition, IMECE 2012
CountryUnited States
CityHouston, TX
Period12/11/912/11/15

ASJC Scopus subject areas

  • Mechanical Engineering

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