Influence of thermal exposures on phase evolution in 12Cr-1Mo-0.35V steel

In this work, the effect of time-temperature annealing parameters on phase occurrence and phase chemical composition changes was examined in 12Cr-1Mo- 0.35V steel. The phase analysis was carried out by energy dispersive X-ray spectroscopy (EDX) and electron diffraction (SAD). Experimental results of phase occurrence have been compared with their equilibrium data calculated using PD-pp program based on the Hillert-Staffansson model. The same proced ure was used for evaluation of chemical composition changes of the phases. After annealing at 500-700 degreesC for 100-5000 hours, the M23C6, Laves an d MX secondary phases were identified. The M23C6 carbide was found to be th e majority phase; together with MX they have been detected in all states. S tatistically significant occurrence of Laves phase was found at temperature s up to 620 degreesC; at 650 degreesC it was found aft;er 5000 hours of ann ealing only.