Cyclic creep behaviour and strain classification of a bainite 2.25Cr-1Mo
steel at 455oC
Uniaxial static and cyclic creep tests are carried out on a bainite
2.25Cr-1Mo steel at 455°C. The dependence of cyclic response on varied
unloading conditions is investigated, with unloading rates from 0.6
MPa/s to 39 MPa/s and the valley stress duration from 0 to 30 min.
Fracture surfaces of each specimen are analysed by using a scanning
electron microscopy, and a systematic classification of strain
components under cyclic creep is proposed to determine the actual
damage. The results indicate that, the fracture modes under static and
cyclic creep conditions both have ductile features. Due to the effect of
anelastic strain recovery, the strain accumulation rate under cyclic
creep is significantly retarded as compared with static creep, and the
unloading conditions apparently influence the behaviour of anelastic
strain recovery. Moreover, a life prediction method for cyclic creep
tests based on mean actual strain deducted recovery strain is proposed.