Inconel 718 N07718 2.4668 NiCr19Fe19Nb5Mo3  Nickel Alloy

Introduce
Inconel 718 is an age-hardenable Alloy-chromium alloy that combines corrosion resistance with high strength and good fabricability. It has high creep-rupture strength at temperatures up to 700 ºC. Its excellent relaxation resistance contributes to its application in springs.

Application
The alloy is used in jet engine and high-speed airframe parts such as wheels, buckets and spacers, and high-temperature bolts and fasteners. Inconel 718 is also used in the oil and gas drilling and production industries due to its high strength and resistance to chlorides, stress corrosion and sulfide stress cracking. Within these industries the alloy has been used for valves, pump shafts and wellhead components.

Standards
718 Sheet, Coil and Plate: UNS N07718, AMS 5596, ASTM B 670, ASME SB 670, B50TF14,
718 Round Bar: UNS N07718, AMS 5662, ASTM B 637, B50TF15, B50809D (Power Generation)
other:AMS 5662, AMS 5663, AMS 5832, AMS 5962, ASTM B637, GE B14H89, ISO 15156-3, (NACE MR 0175)

Key Features
Good creep rupture strength at high temperatures
Higher strength than Inconel X-750
Better mechanical properties at lower temperatures than Nimonic 90 & Inconel X-750
Age hardenable
High temperature dynamic applications

Chemical Composition

Heat treatments
Heat treatments may be adjusted to give required properties. For the best combination of tensile and stress rupture properties, the following quite complex cycle is recommended :
1 hr at 1750/1800ºF (955/980ºC) and air cool, then 8 hrs at 1325ºF (720ºC) and cool at 100ºF/hr (56ºC/hr) to 1150ºF (620ºC), hold for 8 hrs and air cool.
For the best room temperature and cryogenic tensile properties, the cycle is :
1-2hrs at 1950ºF (1065ºC) and air cool, then 8 hrs at 1325ºF (720ºC) and cool at 100ºF/hr (56ºC/hr) to 1150ºF (620ºC), hold for 8 hrs and air cool.

Hot Forming
Because of its strength, INCONEL alloy 718 is more resistant than most materials to deformation during hot forming. It is readily hot-worked if sufficiently powerful equipment is used. Hot forming is performed in the 1650°-2050°F temperature range. In the last operation, the metal should be worked uniformly with a gradually decreasing temperature, finishing with some light reduction in the 1650°-1750°F range. This procedure is necessary to ensure notch ductility in stress-rupture applications when material has been annealed and aged.

Cold Forming 
INCONEL alloy 718 can be cold-formed by standard procedures used for steel and stainless steel. 

Machining
INCONEL alloy 718 can be readily machined, but its high strength and work-hardening characteristics must be considered in the selection and use of proper tool materials and design, operating speeds, and coolants. When machined in the age-hardened condition the alloy will have a slightly better finish; chip action on chipbreaker tools will be better. The use of annealed material, however, provides easier machining and longer tool life.

Super-Plastic Forming
This alloy, designated INCONEL alloy 718SPF, is available as annealed sheet in thicknesses from 0.02 to 0.08 inches (0.5 to 2.0 mm) in widths up to 36 inches (914 mm). The specification SAE AMS 5950 was developed to define the requirements for the alloy.