A study of the creep behavior of modified 9Cr–1Mo steel using continuum-damage modeling

A micromechanical model is developed for the evaluation of creep deformation and rupture times of modified 9Cr–1Mo steel specimens. Creep deformation in metals is generally induced by the dislocation generation, motion, and annihilation. To evaluate the creep behavior of the modified 9Cr–1Mo steel the Orowan’s equation was employed, which is valid for both glide and climb-controlled dislocation movement. The evolution of the dislocation density was modeled by considering the generation and annihilation of single and dipole dislocations. In addition to dislocation motion as a basis for creep deformation, there are several other factors which determine the creep resistance of this steel. Among these, the most significant are precipitate coarsening, solid solutions depletion, and void/crack nucleation and growth. The evolution of these mechanisms during creep deformation was accounted for by introducing specific continuum damage terms. Creep tests were also performed at several stress and temperature levels. The comparison of the numerical model results with the experimental data showed satisfactory agreement.