GRAIN-BOUNDARY SEGREGATION AND CO-SEGREGATION BEHAVIOR OF THREE ELEMENTS IN STEEL 2.25Gr1Mo

Both thermally induced and stress-driven segregation behavior of P, Mo and Cr were experimentally studied in steel 2.25Cr1Mo. The relationship between Mo and P, Cr and P were analyzed. Results of specimens solution treated at 1050°C and held at 540°C show that the concentration of Mo at grain boundary increased with increasing concentration of P during aging, and that the experimental data dots of Mo and P relationship were distributed in a linear zone, whereas, the data dots of Cr and P relationship were scattered. It is concluded that the non-equilibrium grain boundary co- segregation (NGCS) of Mo and P occurred, and the NGCS of Cr and P did not occur during aging in steel with the above heat treatment history. Results of tension test show that both the NGCS of Mo and P, and NGCS of Cr and P occurred under low stresses 30MPa at 500 °C. And the typical multi-elements NGCS of P-Mo-Cr occurred during aging. It is clear that the three elements P, Mo and Cr in steel 2.25Cr1Mo are interactional and inter-promoted.