Microstructural evolution in 12% Cr heat-resistant steel during compression deformation at 650°C

Abstract

ABSTRACTThe 12% Cr heat-resistant steel used for critical components of fossil-fired power plants works in high-temperature and high-pressure steam environments for a long time and inevitably undergoes a certain amount of plastic deformation during service. This plastic deformation will affect the microstructure and hot ductility of the heat-resistant steel and ultimately influence its service life. Therefore, the effect of hot compression deformation on microstructural evolution at 650°C was investigated in this work. As the amount of hot compression deformation increased, the number of subgrains significantly increased, and their sizes gradually decreased. When the amount of deformation reached 50%, dynamic recrystallization occurred, forming a preferred orientation in the rolling direction. and fiber texture appeared in the microstructure when the deformation amount reached 8%, and the intensity of texture was significantly higher than that of texture. Their intensity values further increased with the increase of the amount of deformation. As the amount of hot compression deformation increased, the deviation angle of the Kurdjumov–Sachs (KS) orientation relationship between M23C6 particles and α-Fe gradually increased. Their KS orientation relationship began to be disrupted at the deformation amount of 6% and was completely destroyed at the deformation amount of 20%. With the amount of deformation increasing up to 50%, there were no micropores at the M23C6/matrix interfaces, and no hot cracking occurred. This was mainly attributed to the occurrence of dynamic recrystallization which alleviated stress concentration at the particles /matrix interfaces. The mechanisms of microstructural evolution involving subgrains, grain boundary characteristics, texture evolution, strain distribution, and orientation relationship were discussed in detail.

Keywords

• Heat-resistant steel
• hot compression deformation
• subgrain
• texture
• orientation relationship