Effect of thermal aging on microstructure and element migration of Sanicro25 steel/P92 steel dissimilar steel welded joint
The microstructure changes and element migration of the dissimilar welded joints after aging will have an impact on its service safety.In this paper,Tungsten Inert Gas welding was used to weld Sanicro25/P92,the welding wire is ERNiCrCoMo-3.The welded joints were aged at 650 ℃ for 500,1 000,and 2000 h,and then observe the effect of aging on microstructure evolution and element migration of welded joints.The results show that the micro-organization varies greatly in different regions of the welding section.The microstructure of P92 steel is divided into P92 steel heat-affected zone(HAZ)and P92 steel non-heat-affected zone(Non-HAZ).After aging,the grain size in the microstructure increases,and the number of Laves phases increases,mainly distributed on the crystal boundary;And the δ ferrite was observed in P92 CGHAZ of the welding,after aging,the number of δ ferite gradually increased to form the δ ferite region.The microstructure of Sanicro25 steel and weld are austenitic grain and dendritic structures,respectively.The obvious change of the microstructure of Sanicro25 steel does not occur after the aging,and the crystal boundary in the weld microstructure is more obvious.Element migration occurred at the interface between P92 steel and weld.After aging for 2 000 h,the element migration tended to be stable.After aging,the hardness of the welding section P92 CGHAZ decreases at most.
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