Inconel 718 is a nickel-chromium-molybdenum alloy designed to resist a wide range of severely corrosive environments, pitting and crevice corrosion. This nickel steel alloy also displays exceptionally high yield, tensile, and creep-rupture properties at high temperatures. This nickel alloy is used from cryogenic temperatures up to long term service at 1200° F. One of the distinguishing features of Inconel 718’s composition is the addition of niobium to permit age hardening which allows annealing and welding without spontaneous hardening during heating and cooling. The addition of niobium acts with the molybdenum to stiffen the alloy’s matrix and provide high strength without a strengthening heat treatment. Other popular nickel-chromium alloys are age hardened through the addition of aluminum and titanium. This nickel steel alloy is readily fabricated and may be welded in either the annealed or precipitation (age) hardened condition. This superalloy is used in a variety of industries such as aerospace, chemical processing, marine engineering, pollution-control equipment, and nuclear reactors.
What are the characteristics of Inconel 718?
· Good mechanical properties – tensile, fatigue and creep-rupture
· Yield tensile strength, creep, and rupture strength properties are exceedingly high
· Highly resistant to chloride and sulfide stress corrosion cracking
· Resistant to aqueous corrosion and chloride ion stress corrosion cracking
· High temperature resistant
· Age-hardenable with a unique property of slow aging response that permits heating and cooling during annealing without the danger of cracking.
· Excellent welding characteristics, resistant to postweld age cracking
Chemical Composition, %
| Ni | Fe | Cr | Cu | Mo | Nb | C | Mn | P | S | Si | Ti | Al | Co | B |
| 50.00-55.00 | Remainder | 17.00-21.00 | .30 max | 2.80-3.30 | 4.75-5.50 | .08 max | .35 max | .015 max | .015 max | .35 max | .65-1.15 | .20-.80 | 1.00 max | .006 max |
In what applications is Inconel 718 used?
· Chemical processing
· Aerospace
· Liquid fuel rocket motor components
· Pollution-control equipment
· Nuclear reactors
· Cryogenic storage tanks
· Valves, fasteners, springs, mandrels, tubing hangers
· Well head completion equipment and blow out preventers (BOP’s)
· Gas turbine engine parts
ASTM Specifications
| Sheet/Plate | Bar | Wire |
| B670 | B637 | - |
Mechanical Properties
Typical room temperature properties, 1800°F annealed condition
| Ultimate Tensile Strength, psi | .2% Yield Strength psi | Elongation % | Hardness Rockwell B |
| 135,000 | 70,000 | 45 | 100 |
