High-strain high-temperature fatigue properties of a 0·5Cr–Mo–V steam turbine casing steel

Abstract

AbstractAbstractThe high-strain high-temperature fatigue behaviour of a cast 0·5 Cr–Mo–V steel for steam turbine casings has been evaluated extensively in tests lasting several years. The results define the influence of strain range, dwell period, fatigue-cycle shape, and test temperature on the cyclic endurance. The effect of these parameters on the peak stress and on the stress-relaxation behaviour is also described. A comprehensive review of the data available for Cr–Mo and Cr–Mo–V casing steels suggests that they all have similar resistance to high-strain high-temperature fatigue cracking. An accurate description of the data, facilitating interpolation and extrapolation, is given by ihe relationship established between dwell period and cyclic endurance. However, comparative evaluation of creep–fatigue damage accumulation models together with metallographic examination of test specimens indicates that the life-fraction rule provides the best method of predicting the behaviour of steam turbine components in service.