关键词: GH3625合金棒材, 固溶处理, 时效, 显微组织, 拉伸性能, 高温持久性能, 冲击性能

Abstract: Through vacuum induction melting, argon-shielded electroslag remelting, forging and heat treatment, the GH3625 alloy bars with diameter of 148 mm and 84 mm for nuclear power were trial produced. The microstructure, room and elevated temperature tensile tests, high-temperature rupture and creep tests were conducted on the bars under solution treated state, and then the microstructure and toughness characteristics were conducted on the bars solution treated and aged. The results show that both the microstructures of the bars with diameter of 148 mm and 84 mm are single-phase austenite with duplex grain sizes, and the average grain size of the bar with diameter of 84 mm is slightly smaller. The inhomogeneity of grain increases with the extension of aging time. The grain size aged at 780 ℃ is finer, but the precipitation of carbides is more serious at the same time. The room-temperature tensile strength of the bar with diameter of 84 mm is higher than that of 148 mm, and the plasticity is equivalent between the two; the high-temperature tensile properties of the bar with diameter of 84 mm is generally better than that of 148 mm. With the increase of tensile test temperatures, the tensile strength shows a significant decrease trend, the percentage reduction of area shows an upward trend, and the elongation ascends firstly and then descends. The creep rupture life of the bar with diameter of 148 mm is 857 h and 244 h under the test conditions of 780 ℃/150 MPa and 920 ℃/45 MPa, which means good high-temperature creep plasticity. The impact absorbed energy of the bar aged at 560 ℃ is greater than 300 J, which decreases continuously as the aging time increases at 780 ℃ and 920 ℃, and the impact property of the bar aged at 780 ℃ is the poorest.

Key words: GH3625 alloy bars, solution treatment, aging, microstructure, tensile properties, high-temperature rupture properties, impact property