Study On High Temperature Aging Property Of Sanicro25 And Microstructures And Properties Of Sanicro25/T92 Welded Joints

With the continuous progress of the society and economy,the demanding for energy is also growing fast.Nowadays,more and more methods are applied to improve the efficiency of energy and the thermal efficiency of the unit due to the lack of energy and environment pollution.As a result,it is an inevitable trend to develop the Ultra Supercritical Unit(USC)power generation technique.As the parameters in the Ultra Supercritical Unit are improving,it takes more requirements for high temperature materials.Sanicro25 steel possesses excellent high temperature strength and corrosion resistance,thus.It is the significant candidate material of superheater and reheater in the 630~650oCcritical Unit.Firstly,the high temperature aging property of Sanicro25 steel were studied.Different aging durations,which consists of 100、500、1000 and 2000 h,were taked into account when testing in 650 oC environment.The results showed that the Sanicro25 steel had excellent stability at high temperature and the fine mechanical properties after high temperature aging treatment.Then,the Sanicro25/T92 dissimilar steel welded joints were prepared through gas tungsten arc welding(GTAW),using three Ni-based welding wires.The effect of welding wires on microstructures and mechanical properties of the welded joints was studied.The bright white block ferrite was observed in the T92 side fuse zone of the Sanicro25/T92 welded joints.A further study was applied to ensure the distribution,property,and genesis of δ ferrite.The results revealed that the bright white block ferrite,which is Cr-rich high-temperature δ ferrite,is distributed along the fusion zone.The carbon migration and the chemical constituents of T92 contribute to the generation of δ ferrite.Finally,the creep tests of Sanicro25/T92 welded joints in 650 oC were done under different load stress levels.All the rupture regions were located at T92 material part.Because the rupture time was not long enough to show the creep characteristics of fracture.During the creep test,the dimples initiated,aggregated and fractured.The rupture mode belonged to plastic fracture.