Steady-state creep in a 25 wt % Cr-20 wt % Ni austenitic stainless steel

Abstract

Steady-state creep behaviour of a 25 wt % Cr-20 wt % Ni stainless steel without precipitates was studied in the stress range 9.8 to 39.2 MPa at temperatures between 1133 and 1193 K. The results of stress-drop tests indicate that, in the steady-state creep region, diffusion-controlled recovery creep is dominant. Such recovery creep can be accounted for in terms of the composition of the internal stress,σ _i=σ_s+σ_c, except in the case of fine-grained specimens where d<80 μm, whered is the mean grain diameter,σ _s is possible to reduce easily and is comparable to the driving stress for creep, andσ _c is the persistent stress field due to metastable substructure. In the fine-grained specimens, it is suggested that the steady-state creep is dominantly controlled by grain boundaries.