High-temperature low-cycle fatigue characteristics of the 12Cr10Co3MoWVNbNB turbine rotor steel

Abstract

Low-cycle fatigue (LCF) experiments of the 12Cr10Co3MoWVNbNB steel at 598 °C and a strain amplitude ranging from 0.27 % to 0.55 % were executed to reveal the fatigue characteristics, fatigue fracture mechanism, and further to predict the high-temperature fatigue life of the new-style turbine rotor steel. The results indicate that the steel exhibits a high-temperature fatigue softening characteristic. During the high-temperature LCF, the cracks are generated at surface or subsurface defects of the specimens, and the fatigue striations and dimples are apparent on the fracture surfaces of the crack propagation zone and the final fracture zone, respectively. The Smith-Watson-Topper (SWT) and Manson-Coffin models are suitable to predict the high temperature fatigue life of the steel at high/low strain amplitudes, respectively. In terms of finite element analysis of the turbine set rotor, it is determined that the steady state strain of the rotor steel is approximately 0.2 %. And thus, the fatigue life of the steel rotor is estimated as 172,500 cycles at the strain amplitude, based on the Eq. (6) in this work. After 100,000 cycles at the strain amplitude, the yield and tensile strengths of the steel specimens are only reduced by 1 % and 3 %, respectively, indicating a long residual life, which is consistent with the above predicting result.