On the nature of internal interfaces in a tempered martensite ferritic steel and their evolution during long-term creep

Orientation relationships between ferrite micrograins in a 12% Cr tempered martensite ferritic steel are characterized before and at intermediate times during long-term creep (120 MPa at 550 °C) up to ∼140,000 h. Orientations inherited from the martensitic microstructure during tempering deviate significantly from the well-known/idealized orientation relationships. The observed relationships between micrograins persist throughout creep. The spatial densities of former sub-block, block, and packet boundaries all decrease during creep, suggesting that coarsening takes place on all microstructural scales.