| A fourth-generation high-temperature gas-cooled reactor（HRGR）developed independently in China,uses a GH3625（hereinafter referred to as 625 alloy）nickel-base superalloy as the main component of the control rod system.The alloy undergoes the high temperature aging process under the actual working conditions,which may cause problems such as the stability of the structure and high temperature creep properties.High temperature creep will affect the accuracy of the control rod system components and the flexibility of the component movement.Therefore,it is of great significance to master the microstructure evolution law and the creep variation characteristics after aging of 625alloy in the high temperature aging process,and to select the materials and control the safety threshold of the main components of the control rod system.In this dissertation,625 alloy was selected as the research object,and the aging behavior of the material under high temperature service conditions was studied.The main cut-in point wasδ-Ni3Nb phase.The metallographic microscope（OM）,scanning electron microscope（SEM）and transmission electron microscope were used.（TEM）and other modern analytical methods to study the precipitation mechanism and evolution law ofδphase under different aging conditions of 625 alloy,focusing on the interrelation between the microstructure evolution and high temperature mechanical properties,and applying the electronic creep testing machine to the 625 alloy aging condition.The solid solution samples were subjected to high-temperature creep tests at the same temperature and stress to investigate the variation of creep performance under different aging conditions.The main results of the experimental study show that:（1）When aging time is560°C-920°C and the aging time is 240h,with the increase of aging temperature,the main precipitation phases of 625 alloy aging areγ"phase andδphase;the aging temperature is At 650°C,the time for the precipitation of theδ-Ni3Nb phase in the crystal is about 600 h.When the aging time is 1000 h,the content ofδ-Ni3Nb phase tends to be stable.When the aging temperature is 780°C,theδ-Ni3Nb phase starts to precipitate inside the crystal.The time is about 100 h,and the microhardness value gradually increases.（2）The creep performance and solidification after aging at 560°C due to the different content and distribution ofδphase in the aging process under the creep condition of780°C34.8MPa240h The creep performance of the solution is close to that of 780°C.The creep performance after aging at 780°C is better than that of solid solution.The creep performance at 920°C is inferior to that of solid solution. |
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