Critical Assessment of Short-Term Stress-Relaxation Studies for the Prediction of Creep Properties of P91 Steel

An attempt has been made to interrelate the predicted creep-rupture properties using stress relaxation tests (SRT) with those obtained from uniaxial monotonic creep tests in P91 steel. Stress-relaxation tests were performed at specified total strain levels of 1.3 and 2.5% for fixed duration of 24 h at 873 K. The results from SRT have been used to predict the rupture life using Monkman–Grant relation and Gill–Goldhoff correlation for the steel. Further, the observed stress-relaxation behaviour has been described appropriately using an analytical model with suitable parameter values related to activation volume and activation energy.