Nickel Alloy 718

Quick Facts

Alloy 718 is an austenitic nickel-based super alloy which is used in applications requiring high strength to approximately 1400°F (760°C) and oxidation resistant to approximately 1800°F (982°C). Alloy 718 exhibits excellent tensile and impact strength even at cryogenic temperatures. High strength at room and elevated temperatures is developed by a precipitation heat treatment at 1325°F (718°C) with cooling and a hold of 1150°F (621°C). The relatively slow response to precipitation hardening permits repair welding of Alloy 718 even in aged condition.

Typical Applications

  • Aircraft turbines
  • Gas turbines
  • Fasteners
  • Spacers
  • Oil & gas applications
  • General high strength applications

Stock Range

We stock a comprehensive range of round bars between 22mm and 142mm in diameter and flat bars with thickness of 15mm-60mm and width of 20mm-160mm.
We also offer:

  • General forgings
  • Rings
  • Blocks

Primarily manufactured in: Europe, US

Industry Specifications

  • AMS 5596, 5597, 5583, 5589, 5590, 5662, 5663, 5664, 5832
  • ASME SB-637, SFA-5.14
  • ASTM B670, B637, B1014
  • German Material no.: 2.4668
  • UNS N07718

Material may also be supplied to customer specifications, subject to enquiry.

Melting Practices

  • VIM/ESR or VAR
  • EF/AOD or VOD/VAR
  • Triple Melted

Chemical Analysis

Alloy 718 is hardened by the precipitation of secondary nickel- (aluminium, titanium, niobium) phases,
giving the alloy a combination of high strength and good corrosion resistance.Chemical Composition, %

Mechanical Properties

Machinability

Alloy 718 is distinguished from other nickel–based alloys by its composition and microstructure. Lower alloyed materials have a more uniform structure, and hence depict better machining behavior. Due to its high strength and work hardening characteristics, tooling, operating speeds and coolants should be considered.

Machinability

There are generally two heat treatments used for Alloy 718:

  • Solution annealed between 1021 and 1038°C (1870°F – 1900°F) followed by rapid cooling andprecipitation hardened around 778°C (1432°F)
  • Solution annealed between 941 and 1010°C (1726°F – 1850°F) followed by rapid cooling and precipitation hardened at 718°C (1324°F). Furnace cooled to 621°C (1150°F) for further age applications (often referred to as API 6A 718). The high strength version is being seen increasingly in oil field applications due to increasingly demanding environments.

Corrosion Resistance

Alloy 718 has excellent corrosion resistance in a range of environments including sea water, HS2, CO2, elemental sulphur and chloride ions over various temperatures. It is resistant to sulphide stress cracking and is capable of passing the sulphide stress corrosion test in accordance with NACE TM 0177 Method C solution A.

Typical results:

  • Critical Pitting Temperature 0-5◦C (32-41◦F) ASTM G48 Method C
  • Crevice Corrosion Temperature 40-45◦C (104-113◦F) ASTM G48 Method D
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