EBSD parameter assessment and constitutive models of crept HR3C austenitic steel

Creep damage and evolution of HR3C steel at 650 °C were investigated using electron backscatter diffraction (EBSD), and EBSD-based parameter assessments were conducted. EBSD analyses show that the grain size is almost unchanged and no obvious texture formed after creep at different creep rates. The lowest proportion of low \(\Sigma\) coincidence site lattice grain boundaries under 150 MPa implies that the primary twin structures are preserved under the low stress level, while some twin structures evolved into general grain boundaries at the high creep level. Two main damage features of microcracks and cavities can be seen along the grain boundaries: the former emerged at higher stress levels, while the latter appeared at the lower stress level, and both were shown under medium stress. Band contrast shows that the most severe creep damage is present at 170 MPa. It implies that the creep mechanism differs distinctly under different stress levels, and the transition point is around 170 MPa. Kernel average misorientation is better to describe the local plastic deformation related to the strain distribution while grain reference orientation deviation describes the inhomogeneous strain distribution. Creep lifetime prediction models including the isothermal method, Larson-Miller parameter method and Monkman–Grant relation were evaluated by the experimental data and literature data, and they are valid for predicting creep behavior.