Creep Deformation Behavior, Microstructure Evolution, and Damage Mechanism of Super304H ODS Steel

Abstract

In this paper, the creep deformation behavior, microstructure evolution, and damage mechanism of Super304H oxide dispersion strengthened (ODS) steel have been systematically investigated at 650 °C. The creep behavior of the ODS steel could be understood by virtue of a dislocation creep deformation mechanism. Interrupted creep experiments under 100 MPa were conducted to further study the microstructure evolution during long-term creep deformation. The grains began to refine at the initial stage, and some M23C6 phases were observed at grain boundaries, which enhanced the microhardness during the first creep stage. Along with creep, both Y2O3 and Cu-rich precipitates exhibited good coherence with the matrix. The Y2O3 precipitates showed better thermal stability than the Cu-rich phase. During the second creep stage, some cavities emerged around the M23C6 phase and at grain boundaries. The cavities gradually developed into significant cracks, causing the steel to fracture. The creep damage due to cavity growth could be determined according to the creep damage tolerance factor value.