Low stress dislocation creep mechanism in TiN dispersion hardened 20%Cr-25% Ni stainless steel

Consideration is given to the dislocation creep mechanism in TiN dispersion hardened 20% Cr-25% Ni stainless steel at applied stresses between the threshold and transition stresses. A model for the creep rate is presented as a function of the time required for climb bypass in combination with the ratio between the numbers of particles surmounted by Orowan and by climb bypass. That ratio is shown to be dependent on stress, and this dependence can be quantified on the basis of the distribution of interparticle spacings combined with a model of the source shortening. Consideration is given to the creep behaviour following small stress changes within the regime below the transition stress. It is shown that the predictions of the model are only partially in accord with observation, and this is attributed to inadequacies in the description of the time for climb bypass. (author)