EQUILIBRIUM GRAIN-BOUNDARY SEGREGATION OF PHOSPHORUS IN 2.6CR-0.7MO-0.3V STEELS

The equilibrium grain boundary segregation of phosphorus in two 2.6Cr- 0.7Mo-0.3V steels with 0.06 and 0.005 wt% of C tempered at 823, 853 an d 913 K was investigated. Auger electron spectroscopy was used to esta blish the grain boundary concentrations of the P, C, Cr, Mo and V. Che mical compositions of the carbides were determined by means of EDX/STE M. The standard McLean's theory and Guttmann's theory of co-segregatio n were used to analyze the experimental data. The values of Delta H-p, Delta H-Mo, Delta G(p)(0), Delta G(Mo)(O), and alpha(MoP) were calcul ated. The value of interaction coefficient calculated according to Gut tmann's theory is low to suppose the influence of molybdenum upon the P segregation. The more expressive changes in the grain boundary conce ntrations of P and C in relation to tempering temperature were found o ut in the steel with levier C content.