Deformation and fracture processes during creep of 12Cr12Mo14V ferritic steel

The creep and fracture properties of $\text{1}\text{2}\text{Cr}\text{1}\text{2}\text{Mo}\text{1}\text{4}\text{V}$ ferritic steel have been determined over the stress range 125 to 362 MNm^?2 at 838 K using high precision, constant stress equipment. When the variation of the rupture life, t_f, and the secondary creep rate, $\text{?}\text{dot}{}_{\mathrm{<mtext>s</mtext>}}$, with stress, σ, was described as ${}_{\mathrm{<mtext>f</mtext>}}\text{α}\text{?}\text{dot}{}_{\mathrm{<mtext>s</mtext>}}\text{ασ}{}^{\mathrm{n}}$ a stress exponent of was recorded. Comparison with long term data then established that, at stresses below ～ 100 MNn^?2, n decreased gradually until values close to unity were obtained at stresses approaching those encountered in electricity generating plant. This decrease in stress exponent is shown to be attributable to a progressive loss of creep resistance associated with changes in carbide dispersion rather than to any change in the mechanisms by which deformation and failure occur.