High-temperature creep property deterioration of the alumina-forming austenitic steel: Effect of σ phase

Abstract

The microstructural evolution of the alumina-forming austenitic (AFA) steel subjected to different cold rolling reductions during creep test at 973 K and 120 MPa was investigated by multiple characterization methods, and the high temperature creep property was also examined. It was found that the creep property of CR10 sample is not satisfactory although cold rolling truly improved it. The creep cavities were observed to nucleate at the interface between B2–NiAl phase and σ phase in the δ-ferrite. The serious coarsening of B2–NiAl phase and σ phase in δ-ferrite was considered as the main factors for the decline of creep property. In addition, the results also suggested that the shape of B2–NiAl phase changes from round to plate with increasing creep time, which resulted from the increase of elastic strain energy. Simultaneously, it was noteworthy that σ phase always grows adjacent to plate-shape B2–NiAl phase, which indicates the coarsening of σ phase is inseparable from that of B2–NiAl phase.