Creep behavior of 2.25Cr1Mo steel—Effects of thermal ageing and pre-strain

Effects of thermal ageing and pre-strain on the shape of creep curves of 2.25Cr1Mo steel have been studied. Analysis revealed that the thermal ageing increases the tendency to soften but not the pre-strain. Softening due to carbide coarsening thus appears to be the dominant mechanism of creep. Over a range of stress and temperature, creep data were generated under different microstructural conditions and collected from literature to examine the potential of the mechanism-based model used for predicting creep behavior. A fairly accurate prediction of creep life up to 5% strain is achieved using eight materials constants extracted from the creep curves of steel having similar initial microstructure. The limitation and reliability of the model used to assess creep behavior of service-exposed steels have been discussed.