High-temperature structure stability and mechanical properties of novel 718 superalloy

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 452; pp. 584 - 591
• Main Authors: Du, J.H., Lu, X.D., Deng, Q., Qu, J.L., Zhuang, J.Y., Zhong, Z.Y.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.04.2007; Elsevier
• Subjects: Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder; Creep; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Mechanical properties; Novel 718 superalloy; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Stress rupture; Structure stability; Novel 718 superalloy; Mechanical properties; Stress rupture; Structure stability; Creep; Nickel base alloys; Strengthening; Tetragonal lattices; Phase transformations; SAED; High temperature; Superalloys; Heat treatments; Hardening; Transmission electron microscopy; Orthorhombic lattices; Chemical composition; Microstructure
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2006.11.039

Phase transformation from γ″ (bct) to δ (orthorhombic) at 650 °C or elevated temperature is the main obstacle preventing the conventional In 718 alloy from elevated temperature applications. A kind of novel 718 alloy, which offers 30 °C temperature advantage over conventional In 718, was designed and fabricated by adjustment of chemical composition which included the increasing in content of Al + Ti, the ratio of Al/Ti and the level of P and B. Microstructure of the novel 718 alloy at as-heat treated condition was studied. Variety and morphology of the strengthening phase were evaluated by SEM, TEM and SAED observations. High-temperature structure stability and mechanical properties of the novel 718 alloy were examined after long-term exposure at 680 °C. Results indicate that the strengthening phases in novel 718 alloy are spherical morphology γ′-phase and sandwich γ′ + γ″-phases. The unique structure makes this novel 718 alloy have excellent high-temperature structure stability and mechanical properties compared to the conventional In 718.