In this study, the influence of thermal aging and notch on low-cycle fatigue strength of forged mod. 9Cr-1Mo steel was investigated at elevated temperature. Total strain-controlled low-cycle fatigue tests using the smooth specimen and load-controlled low-cycle fatigue tests using the notched specimen were carried out at 873K in air. The triangular, tension-hold and compression-hold trapezoidal waveforms were applied to the specimens in a series of the tests. From the experimental results, there is no effect of the thermal aging on strain-controlled low-cycle fatigue life using the smooth specimen with each strain waveform. However, low-cycle fatigue life of the notched specimen decreased by thermal aging under load-controlled condition with triangular and tension-hold trapezoidal waveform.
