Effect of processing parameters on the evolution of dislocation density and sub-grain size of a 12%Cr heat resistant steel during creep at 650 °C

The influence of hot-deformation and tempering temperature on the microstructure evolution of a 12%Cr heat resistant steel during short-term creep at 80–250 MPa and 650 °C was investigated. Quantitative determination of dislocation density and sub-grain size in the initial microstructure and after creep was investigated by STEM-HAADF. A correlation between microstructure evolution and creep response is established. All crept samples showed a significant increase of sub-grain size and a reduction of dislocation density. Hot-deformed samples showed better creep strength than non hot-deformed samples due to homogenization of the microstructure. The tempering temperature affected the dislocation density and the sub-grain size evolution, influencing the creep behavior.