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Vol.62, No.1, 32 ~ 39, 2024
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| Title |
| Effect of Heat Treatment Temperature on Microstructure, Tensile Properties and δ-Precipitate Phase in Ni-based Superalloy |
| 송전영 Jeon Young Song , 구지호 Ji Ho Gu , 신종호 Jong Ho Shin , 조원희 Won Hui Jo , 이초현 Cho Hyeon Lee , 설재복 Jae Bok Seol , 마영화 Young Wha Ma |
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| Abstract |
| Here, we investigated the influence of δ-precipitate (orthorhombic D0a Ni3Nb-ordered phase) on the room- and high-temperature tensile properties in wrought nickel-based Inconel 625 superalloys subjected to solution and aging heat treatment. Typically, solution heat-treatment temperatures in these alloys affect the solid-state precipitation of δ-phase, which governs high-temperature tensile properties. While precipitation of fine D0a δ-phase is known to have beneficial effects on the mechanical properties owing to the retardation of grain coarsening, Widmanstatten δ precipitation plays a deleterious influence on the fracture toughness, tensile ductility, and fatigue resistance. Therefore, to enhance the mechanical properties of this alloy series, it is key to generate a high number density of fine D0a δ precipitate by adjusting solid solution treatment temperatures. In this study, solution heat treatments were conducted above and below δ-phase solvus temperatures. By applying solution heat treatment at 900℃ and 970℃, this alloy was confirmed to have a Widmanstatten δ phase and is composed similarly to the annealed microstructure. This Widmanstatten δ precipitate was densely distributed at both intergranular and intragranular grains. On the other hand, when solution treatment was applied at 1040 and 1100℃, more coarse particles (approximately 30 μm) with a significant reduction of Widmanstatten type δ phase were obtained. We found that grain size and Widmanstatten δ-phases have an important role in the high-temperature tensile properties of Inconel 625 superalloy series.
(Received 11 July, 2023; Accepted 9 October, 2023) |
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| Key Words |
| Inconel 625 superalloys, solid solution heat treatment, precipitates, grain size |
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