An Auger electron spectroscopy study of phosphorus and molybdenum grain boundary segregation in a 2.25Cr1Mo steel

Thermodynamics of grain boundary segregation of phosphorus and molybdenum in a 2.25Cr1Mo steel were investigated using Auger electron spectroscopy (AES). After quenching from 980 °C and tempering at 650 °C, the steel samples were aged for different times at 560 °C, 520 °C and 480 °C, respectively, followed by AES measurements. Based on the AES results for equilibrium grain boundary concentrations of phosphorus and molybdenum, it is seen that the interaction between these two elements in segregation is weak and the free energies of segregation are constant, being about 38 kJ/mol and 17 kJ/mol for phosphorus and molybdenum, respectively.