Product Focus – INCONEL alloy 718

If you need high strength and excellent corrosion resistance for demanding environments, INCONEL 718 alloy is worth considering. We'll take a closer look at its specifications.
If your project requires an alloy with ultra-high strength, consider INCONEL 718 alloy. This nickel/cobalt and chromium alloy is a potential choice for a wide range of applications, including rings, casings and formed sheet metal parts for liquid-fuel rockets, aircraft and land-based gas turbine engines, as well as cryogenic storage tanks-all of which require the metal to perform at its best. Its excellent mechanical properties remain consistent over a wide temperature range, from -200°C to 700°C.

In addition to its high strength, INCONEL 718 alloy has good corrosion resistance in a wide range of environments and is well protected against chloride-ion stress corrosion cracking. The addition of chromium to the nickel-based alloy makes it resistant to attack by oxidizing elements and sulfur-containing compounds. Molybdenum, as a supporting element, helps resist pitting corrosion in many cases.

Molybdenum is widely selected because it is a versatile metal that is easy to machine into complex parts. Molybdenum is known for its excellent resistance to post-weld cracking. It is also easy to machine, but its strength must be considered when considering the processing method.

Heat Treatment
The alloy exhibits good tensile, fatigue, creep, and rupture strength in a wide range of conditions. In most cases, INCONEL 718 alloy is specified as solution annealed and precipitation hardened (also known as age hardened). In order to retain the full strength of the alloy, it must be heat treated under very specific conditions. Its hardening is achieved by precipitation of secondary phases (such as gamma-′ and gamma-′ duplex) in the metal matrix. Two common heat treatment methods are generally used for this alloy.

First, for INCONEL 718 alloy, the best heat treatment process is to anneal at 1700-1850°F (about 850-900°C) and then age to obtain the best combination of fracture life, notched fracture life, and fracture ductility. In addition, this process also provides the highest room temperature tensile strength, yield strength, and the highest fatigue strength.

However, if your project requires optimum transverse ductility, impact strength, and low temperature notched tensile strength in thick sections, a 1900-1950°F (approximately 860-900°C) anneal and appropriate aging treatment will be required. This process will produce notched brittleness during stress rupture.

For detailed technical specifications of this alloy, please refer to the Grades section of our website. If you think your project could benefit from INCONEL 718 alloy, please contact a member of our sales team.