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 (epsilon)over dot(m) depending on applied stress sigma 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, sigma(0), into the equation. Furthermore, the construction of constitutive equations of (epsilon)over dot(m) from the PLB region to the power-law (PL) region for 9% Cr heat resistant steels has been shown to be feasible. (C) 2011 Elsevier B.V. All rights reserved.