The effect of secondary precipitation on the creep strength of 9Cr1Mo steel

This paper presents the results of an electron optical examination of laboratory creep tested normalised and tempered 9Cr1Mo steel. Creep takes place by matrix deformation leading to localised areas of a highly recovered dislocation mesh. Within these locally recovered regions, secondary precipitation of an M2X dispersion takes place. Nucleation of M2X relies on a dislocation sweeping mechanism, where the local recovery has allowed dislocation movement. The onset of secondary precipitation leads to a modest increase in creep strength and perturbed stress rupture curves. Evidently, stress rupture extrapolations for design purposes should be re-examined in the light of these findings. (author)