| Title |
Effect of Heat Treatment Temperature on Microstructure, Tensile Properties and δ-Precipitate Phase in Ni-based Superalloy |
| Authors |
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) |
| DOI |
https://doi.org/10.3365/KJMM.2024.62.1.32 |
| ISSN |
1738-8228(ISSN), 2288-8241(eISSN) |
| Keywords |
Inconel 625 superalloys; solid solution heat treatment; precipitates; grain size |
| 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) |