China has the most supercritical boilers in the world. Grade 91 steels are widely used for high temperature components of supercritical boiler. During high temperature service, microstructural evolution of Grade 91 steel may affect the mechanical properties, including creep strength. However, there are very few studies on quantitative assessment of microstructural evolution for Grade 91 steel, especially on precipitates content.
In this article, microstructural evolution of Grade 91 was studied. A quantitative assessment of microstructure evolution was given during long-term creep, focusing on the precipitated phase content in Grade 91 steel. The results show, the precipitates content of Grade 91 steel has a corresponding relationship with creep damage.