On the thermal stability of a 9Cr-ODS steel aged at 700 °C up to 10000 h - Mechanical properties and microstructure

Thermal aging experiments on a 9Cr-ODS steel were carried out at 700 degrees C with a period from 100 up to 10000 h, and the effects on mechanical properties and microstructural evolutions were investigated. It was found that hardness and tensile properties exhibited negligible degradation by thermal aging. The mixed ductile and brittle fracture modes in the tensile specimens remained almost no change. Although a slight recovery of grains/subgrain structures and dislocations took place, the homogeneously dispersed nano-size oxides with an ultrahigh density in matrix were not affected during the thermal aging. However, a significant coarsening of carbides around grain/subgrain boundaries appeared. Benefited from the extreme stability of nano-size oxides, the 9Cr-ODS steel possesses the excellent thermal stability of mechanical properties exposed to the elevated temperature of 700 degrees C up to 10000 h.