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.
Character
lGood mechanical properties – tensile, fatigue and creep-rupture
lYield tensile strength, creep, and rupture strength properties are exceedingly high
lHighly resistant to chloride and sulfide stress corrosion cracking
lResistant to aqueous corrosion and chloride ion stress corrosion cracking
lHigh temperature resistant
lAge-hardenable with a unique property of slow aging response that permits heating and cooling during annealing without the danger of cracking.
lExcellent welding characteristics, resistant to postweld age cracking
Application
lChemical processing
lAerospace
lLiquid fuel rocket motor components
lPollution-control equipment
lNuclear reactors
lCryogenic storage tanks
lValves, fasteners, springs, mandrels, tubing hangers
lWell head completion equipment and blow out preventers (BOP’s)