Microstructural stability and short-term creep properties of 12Cr-W-Mo-Co steel

In this work, the evolution of microstructure during the aging process and short-term creep deformation behavior for 12Cr-W-Mo-Co (12Cr-CC) steel was investigated at 650 °C. The strengthening effects of microstructure were studied based on the crystal structure of precipitation and their coarsening characterization. It is shown that M23C6 and MX types of secondary phases and martensitic laths were coarsened with the proceeding of aging. Fe2(W, Mo) type of Laves phase was precipitated contiguously to M23C6 during the creep process. Needle-like and bulk shape of Laves phases were observed in the aging process. All these precipitates have the size smaller than 500 nm after aging for 3000 h at 650 °C, demonstrating an excellent microstructural stabilization at 650 °C. The creep rates of 12Cr-CC steel under the high stress level at 650 °C reveal that the steel has superior short-term creep deformation resistance, e.g., the creep rate of 12Cr-CC steel is lower than that of 12Cr-2W-CoMoVNb by at least one order under the stress of 250 MPa. The high short-term creep property provides promising perspective for 12Cr-CC steel to be applied for the power plants run under high pressure and temperature.