Effect of Original State of Pipe on Microstructure and Mechanical Properties of FGHAZ of P92 Steel

Taking the new and old P92 pipes as the object, the rod samples of fine grain heat affected zone(FGHAZ)was prepared by using rapid heat treatment process.The microstructure and properties of the two FGHAZ samples were compared through observation by SEM, TEM, microhardness and creep tests, and the effect of the pipe original state on the microstructure and mechanical properties of FGHAZ of P92 steel was revealed. The results show that compared with that of the FGHAZ of new P92 pipe, the dislocation density of the FGHAZ of old P92 pipe is lower, the size of the precipitates is bigger, which decreases the hardness and creep resistance. During creep test, the FGHAZ of the old P92 pipe has higher precipitating tendency of Laves phase, which promotes the formation of creep void, accelerates the creep fracture and shortens the creep rupture life.