a bainite 2.25Cr-1Mo steel at 455oC
Hao Jiang1, Oluwadamilola Olaoluwa Ogunmola1, Zizhen Zhao2, Xu Chen1*
1School of Chemical Engineering & Technology, Tianjin University, Tianjin 300072, China
2School of Mechanical & Automotive Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, China
*Corresponding author:xchen@tju.edu.cn
Abstract: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.
Keywords: 2.25Cr-1Mo steel; static creep; cyclic creep; unloading conditions; anelastic stain recovery