Phosphorus segregation in 2.25Cr–1Mo steel

Abstract

Phosphorus segregation to grain boundaries in a commercial grade 2.25Cr–1Mo steel subjected to a variety of heat treatments has been examined using X-ray spectroscopy in a field emission gun scanning transmission electron microscope. A number of points have been established. Segregation of phosphorus to grain boundaries is present after austenitising and quenching. Tempering for 2 h at 650°C enhances phosphorus segregation during the following aging processes at 520°C. A higher austenitisation temperature (larger grain size) makes subsequent segregation more intense. For specimens austenitised at 1100°C, the concentration of phosphorus segregated to grain boundaries steadily increases with aging time after tempering (from 0 to 210 h). For specimens austenitised at 900°C, the phosphorus concentration at grain boundaries first increases, reaches a maximum at an aging time of ∼ 210 h and then decreases with aging time (480 h).