Abstract
Creep testing was conducted on the pre-crept specimens of a 2.25Cr-1Mo steel under constant load. The amount of pre-strain was between 4.4 and 12.0%, and the range of temperature and initial stress was 853 to 903 K and 78.4 to 127.4 MPa, respectively. The relation between creep rate, ε and creep strain, ε was expressed as below over a wide range of creep strain :ε=εOexp(sε), where s is the acceleration factor, ε0 is the imaginary initial strain rate, and the stress and temperature dependence ofεO is given as:ε0=Aσnexp(-QO/RT), where QO is the apparent activation energy for creep of the magnitude of 400±10kJ·mol-1, σ is the true stress, n is the stress exponent of the magnitude of 9.7 and A is the mechanically defined structure factor expressed as below:A=AOexp[(m-n)εp], where AO is the structure factor for virgin specimens and m is the constant. These experimental facts lead to the conclusion that pre-strain and creep strain do not alter the creep mechanism but cause the increase in the mechanically defined structure factor, and creep life, tr is given by tr=1/ (sεO).
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