The Role of Dislocation Climb across Particles at Creep Conditions in 9 to 12 Pct Cr Steels

摘要

The influence of a distribution of particles on creep strength is analyzed. The time it takes for dislocations to climb across the particles is the basis for a model that can describe the effect of particle size distribution, particle area fraction, stress, and temperature on the creep rate. The degradation of microstructure through coarsening is taken into account. The particle size distributions for M23C6 carbides and MX carbonitrides in a 9 pct Cr steel are accurately represented by an exponential function. Coarsening coefficients and phase fractions for MX and M23C6 particles are predicted using thermodynamic modeling, and show good fit to experimental data. The size distributions are used to determine the amount of dislocations, which can either climb across particles or make Orowan loops. The dislocation climb model is integrated into a creep rate prediction model and is used to reproduce experimental creep data for P92 steel.