Constitutive equations of the minimum creep rate for 9% Cr heat resistant steels

This study addresses the overestimation of the time–temperature-parameter (TTP) method on the allowable creep strength of 9–12% Cr heat resistant steels. Creep data of 9% Cr heat resistant steels are divided into several data sets according to the creep controlling mechanism. Constitutive equations of the minimum creep rate ε ˙ m depending on applied stress σ and temperature T have been constructed, and the modeling results are found to be well in agreement with the experimental data. The influence of the second phase particles in the power-law-breakdown (PLB) region on 9% Cr heat resistant steels is well reflected by introducing a parameter, σ0, into the equation. Furthermore, the construction of constitutive equations of ε ˙ m from the PLB region to the power-law (PL) region for 9% Cr heat resistant steels has been shown to be feasible.