Phosphorus segregation in CrMoV low-alloy steels

The phosphorus segregation at temperatures of 773 and 853 K has been studied in two low-alloy Cr–0.4 Mo–0.5 V steels with different chromium contents (0.85 and 2.5 mass%). Segregation of elements on grain boundaries was measured by means of Auger electron spectroscopy. Transmission electron microscopy techniques were used for the identification of secondary phases in the steels investigated. A significant influence of aging temperature on the kinetics and equilibrium value of phosphorus grain-boundary concentration was observed. Both lower temperature and higher bulk chromium content were found to increase the grain-boundary phosphorus segregation. This is in agreement with the Langmuir–McLean theory, the model of phosphorus–carbon site competition, and also confirms the significant effect of carbide formation on phosphorus segregation in steels.