Parameter correlation of high-temperature creep constitutive equation for RPV metallic materials

Constant-temperature and constant-load creep tests of SA-508 stainless steel were performed at six temperatures, and the creep behavior and properties of this material were determined. Constitutive models were established based on an isothermal creep method to describe the high-temperature creep behavior of SA-508. Material parameter k, stress exponent nσ, and temperature exponent nt of the established constitutive models were determined through experimental data via numerical optimization techniques. The relationship of k, nσ, and nt was evaluated, and a new coefficient model of k-T, nσ-T, nt-T, and nt-nσ was formulated through the parameters of the isothermal creep equation. Moreover, the isothermal creep equation for this material at every temperature point from 450 °C to 1000 °C was obtained from the models. This method can serve as a reference for isothermal creep analysis and provide a way for the safety assessment of components of reactor pressure vessels.