Effect of stress on the creep deformation of ASME Grade P92/T92 steels

Abstract The stress versus strain curve of ASME Grade P92/T92 steels was analysed and the stress dependence of the creep deformation behavior was investigated. Good correspondence between 50% of 0.2% offset yield stress and a proportional limit was observed over a range of temperatures from 550 to 700°C. Stress dependence of the minimum creep rate was divided into two groups of high and low stress regimes with a boundary condition of 0% offset yield stress. Creep deformation in the low stress regime was considered to be controlled by dislocation climb. Large stress dependence of the minimum creep rate in the high stress regime was equivalent to the strain rate dependence of flow stress observed in the tensile test. Creep strength in the high stress regime is assumed to be influenced by plastic deformation, and should be excluded for a long-term creep strength evaluation.