Inconel 718 Wire is an alloy of chromium that may be age-hardened and combines corrosion resistance with high strength and excellent fabricability. Inconel 718 Wire temperatures as high as 700 °C, it possesses a high creep-rupture strength. Its use in springs is facilitated by its superior relaxation resistance.
Heat-Treatment Method
Inconel 718 Wire is bought in the mill- or solution-annealed state. Prior to fabrication and heat treatment, it may in some cases undergo a stress-relief procedure. In the solution anneals, a precipitation (age) hardening process is performed. The material becomes harder as secondary phases (such as gamma prime and gamma double-prime) precipitate into the metal matrix. Nickel-aluminum, nickel-titanium, and nickel-niobium phases precipitate as a result of aging at temperatures between 600 and 815 C (1100 and 1500 F).
The key to the heat-treatment procedure is making sure that these age-hardening elements are completely in solution at high temperatures (i.e., totally dissolved in the matrix), as failure to do so will result in weak precipitation. There are typically two heat treatments (although slight temperature variations of these recipes are often employed). Solution annealing at 925–1010 °C (1700–1850 °F), then swift cooling (usually in water). Following this, the precipitation hardens for eight hours at 720 °C (1,325 °F), the furnace cools to 620 °C (1,150 °F), holds for ten hours, and then the air cools.
Solution anneals at 1040–1065 °C (1900–1950 °F), then quickly cool (usually in water). The precipitation then undergoes a 10-hour period of hardening at 760 °C (1400 °F), a 10-hour period of furnace cooling to 650 °C (1200 °F), and finally, a 10-hour period of air chilling. In order to prevent discoloration, solution heat treatments are normally carried out in vacuum or argon furnaces with low dew points. The grain size of a sheet after 30 minutes of annealing varies depending on temperature (Fig. 2). Additionally, Inconel® 718 ages far more slowly than alloys that have been toughened with aluminum and titanium. The alloy may therefore be heated and cooled over the aging temperature range at typical speeds while maintaining softness and ductility in the majority of sizes.
Key Features
- High temperature creep rupture resistance is acceptable
- Superior to Inconel X-750 in strength
- Better mechanical characteristics than Nimonic 90 and Inconel X-750 at lower temperatures
- Age resistant
- Dynamic high-temperature applications
Application of Inconel 718 Wire
- The alloy is utilized in high-speed airframe components and jet engine parts such as wheels, buckets, and spacers as well as high-temperature bolts and fasteners.
- Due to its high strength and resistance to chlorides, stress corrosion, and sulfide stress cracking, Inconel 718 is also utilized in the oil and gas drilling and production industries.
- The alloy has been used for wellhead components, pump shafts, and valves in various sectors.
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