UNS Number N07718

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.

Available Forms of Inconel 718 at Rooplaxmi Steels:

•           Bar
•           Sheet
•           Plate
•           Pipe & Tube (welded and seamless)
•           Wire

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

 

Inconel 718 Chemical Composition, %:

Ni	Fe	Cr	Cu	Mo	Nb	C	Mn
50.0-55.0	Balance	17.0-21.0	0.30 max	2.80-3.30	4.75-5.50	0.08 max	0.35 max

 

P	S	Si	Ti	Al	Co	B
0.015 max	0.015 max	0.35 max	0.65-1.15	0.20-0.80	1.00 max	0.006 max

 

Application of Inconel 718:

•           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

 

Machining and Fabrication with Inconel 718:

Inconel 718 is hardened by the precipitation of secondary phases (e.g. gamma prime and gamma double-prime) into the metal matrix. The precipitation of these nickel- (aluminum, titanium, niobium) phases is induced by heat treating in the temperature range of 1100 to 1500°F.

Two heat treatments are generally utilized for INCONEL alloy 718:

1. Solution anneal at 1700-1850°F followed by rapid cooling, usually in water, plus precipitation hardening at 1325°F for 8 hours, furnace cool to 1150°F, hold at 1150°F for a total aging time of 18 hours, followed by air cooling.
2. Solution anneal at 1900-1950°F followed by rapid cooling, usually in water, plus precipitation hardening at 1400°F for 10 hours, furnace cool to 1200°F, hold at 1200°F for a total aging time of 20 hours, followed by air cooling

 

Inconel 718 ASTM Specification:

Pipe	Tube	Sheet / Plate	Bar	Forging
AMS 5589, AMS 5590	AMS 5589, AMS 5590	B670	B637	B637

 

Welding Wire Designations:
AWS A5.14 – ERNiFeCr-2

 

Mechanical Properties of Inconel 718:
Typical room temperature properties, 1800°F annealed condition

Ultimate Tensile Strength	135000 psi
Yield	(0.2 % offset) 70000 psi
Elongation	45 %