Effect of Long-Term Thermal Aging on Microstructure Evolution and Creep Deformation Behavior of a Novel 11Cr-3W-3Co Martensite Ferritic Steel

This paper focused on the microstructure evolution under different thermal aging times at 650 degrees C and its effect on creep behavior in 11Cr-3W-3Co heat-resistant steel. After short-term thermal aging at 650 degrees C (>750 h), a Laves phase was found in the regions adjacent to the PAG boundaries, martensitic lath boundaries, and M23C6 carbides, and gradually swallowed adjacent M23C6 carbides with the aging time increased. Higher contents of Si and P are good promoters of the nucleation of the Laves phase during long-term aging. In addition, the coarsening behavior of the Laves phase, M23C6, and MX were investigated. As the aging time increases, the coarsening behavior among precipitated phases in the above-mentioned example exhibits remarkable variability, which is discussed in detail in this paper, and the evolution of the subgrain size was also analyzed in detail. The increasing rate of subgrain size is, in general, consistent with that of the M23C6 carbide size. The evolution of dislocation density in different aging times shows an obvious difference, and the decreasing rate of dislocation density is significantly affected by the precipitated phase after long-term aging time. The creep performance of the material decreases significantly as the aging time increases, which is closely related to the coarsening of the precipitates such as M23C6 carbides and subgrain during long-term aging.

Automated summary

This paper focused on investigating the microstructure evolution and its effect on creep behavior in 11Cr-3W-3Co heat-resistant steel under different thermal aging times at 650 degrees C. Laves phase was found after short-term thermal aging, which gradually consumed adjacent M23C6 carbides as the aging time increased. Higher Si and P contents promoted the nucleation of Laves phase during long-term aging. The coarsening behavior of precipitated phases and the evolution of subgrain size and dislocation density were also analyzed. The creep performance of the material decreased significantly with increasing aging time, which was attributed to the coarsening of precipitates and subgrain during long-term aging.