The role of dispersion hardening in creep of steel 2.2Cr-1Mo-(Nb)

A comparison is made of creep properties and structures of two steels of which one was stabilized with 0.38% of niobium. To make an assessment of the effect of initial structure possible, heat treatment was used to prepare two different structural states. The creep properties were found to be significantly affected by the heat treatment, ie., the initial structure. Niobium stabilization was manifest in a change in the dispersion phase which precipitated in the steels in both creep and heat treatment. The hardening effect of the dispersion is only slightly felt while the presence of Nb atoms in the solid solution stabilizes the dislocation structure. (J.P.)