Grain refinement of P91 steel using double austenitization treatment

Abstract

The effect of conventional normalizing and tempering (CNT) and double austenitization-based normalizing and tempering (DNT) heat treatments on the microstructure evolution and mechanical properties of creep strength-enhanced ferritic P91 steel were studied. CNT treatment was performed at 1,050�C and air cooled for 1 h and also at 760�C and air cooled for 2 h. In double austenitization- based normalizing heat treatment, steel was austenitized at 1,050�C and air cooled for 1 h and then normalized in a temperature range of 950�C -1,150�C for 1 h followed by water quenching. After the double normalizing, tempering is performed at 760�C for 2 h. A DNT treatment resulted in homogeneous microstructure formation that led to improved mechanical properties as compared to CNT treatment. The incomplete dissolution of precipitates in single-stage tempering resulted in incomplete martensitic structure formation. � 2018 by ASTM International.