关键词: N06625合金, 组织, 性能, 长期时效

Abstract: Microstructural and property changes of N06625 alloy seamless tube after solution treatment at 1150 ℃ for 40 min and long-term aging at 750 ℃ were investigated. The results show that during long-term aging at 750 ℃, the grain size of the N06625 alloy remains relatively stable, M₂₃C₆ carbides primarily precipitate along the grain boundaries, while the needle-like δ-phase preferentially forms at the grain boundaries and twin boundaries, subsequently spreading throughout the grain interior, and eventually forming a Widmanstätten-like δ-phase structure. Within the aging time range of 0-3000 h, the room-temperature impact property decreases significantly, while the hardness increases rapidly. However, as the aging time continues to increase, both the room-temperature impact property and hardness tend to stabilize. During long-term aging, the room-temperature impact fracture mechanism of the N06625 alloy changes from ductile fracture to brittle fracture. The extensive precipitation of Widmanstatten-like δ-phase is identified as the primary factor influencing the room-temperature impact property. The N06625 alloy tube exhibits an extrapolated creep strength of 88.036 MPa at 750 ℃ for 100 000 h, satisfying the engineering design requirements of high-temperature gas-cooled reactor.

Key words: N06625 alloy, microstructure, properties, long-term aging