ThePipingMart Blog Grades 718 Inconel Alloy (UNS N07718) – Composition, Properties and Uses

718 Inconel Alloy (UNS N07718) – Composition, Properties and Uses

Inconel 718

Inconel 718 is a type of superalloy that can be used in various applications due to its high strength, corrosion resistance, heat resistance, and physical properties. It is essential for many industries, including aerospace, automotive, and medical. Let’s take a closer look at this unique alloy and explore why it is so important.

Inconel 718 Composition

Inconel 718 comprises nickel-chromium-molybdenum alloy with additions of niobium and Titanium.

Carbon 0.08 max
Manganese 0.35 max
Phosphorus 0.015 max
Sulfur 0.015 max
Silicon 0.35 max
Chromium 17-21
Nickel 50-55
Molybdenum 2.80-3.30
Columbium 4.75-5.50
Titanium 0.65-1.15
Aluminum 0.20-0.80
Cobalt 1.00 max
Boron 0.006 max
Copper 0.30 max
Tantalum 0.05 max
Iron Balance

Inconel 718 Physical properties

718 Inconel is an alloy often used in engineering and aerospace applications requiring a combination of high strength and corrosion resistance. It has a yield strength greater than 90 ksi, making it a material preferred for components and parts requiring considerable strength. The Young’s modulus for Inconel 718 is around 28msi, resulting in good formability, ductility and weldability. Additionally, it has excellent creep-rupture properties at 1300°F and can tolerate temperature extremes ranging from -422°F to 1500°F depending on heat treatment condition. As such, Inconel 718 is often used in high-temperature engine and airframe components due to the robust physical properties that make it an ideal material for challenging engineering conditions.

Solution Treated Solution Treated and Aged
Density 0.296 lb/in3 (8.192 g/cm3) 0.297 lb/in3 (8.22 g/cm3)
Specific Gravity 8.19 8.22
Melting Range 2500-2600°F 1370-1430°C

Inconel 718 Mechanical Properties

This combination gives the alloy excellent mechanical properties like high tensile strength, yield strength, creep resistance, fatigue life, oxidation resistance, and corrosion resistance. The alloy also has good thermal stability, which means it can be used in temperatures up to 1300 degrees Fahrenheit without losing its mechanical or chemical properties.

Yield Strength
 (0.2% offset)
Ultimate Tensile Strength
(% in 2″)
Sheet and strip 80,000 psi (550 MPa) 140,000 psi (965 MPa) 30 (min)
Plate 105,000 psi (725 MPa) 150,000 psi (1,035 MPa) 30 (min)

Solution trated plus precipitation heat treated.

Yield Strength
 (0.2% offset)
Ultimate Tensile Strength
(% in 2″)
150,000 (1,035 MPa) 180,000 psi (1,240 MPa) 12 (min)

Inconel 718 Chemical Properties

The chemical composition of alloy 718 Inconel includes Nickel (58–63%), Chromium (17–21%), Iron (5–9%), Molybdenum (2.8–3.3%) along with other elements such as Titanium (0.65–1.15%), Aluminum (0.2–0.8%), Cobalt (<1%) and Manganese (<1%). These elements give the alloy its unique physical and mechanical properties, making it ideal for many applications where strength and durability are necessary.

Inconel 718 Thermal Properties

Temperature Range Co-Efficients
°C °F W/m.K Btu.ft/°F
0-100 532-212 6.5 11.2

Inconel 718 Equivalent

  • Solution Treatment: 1800°F (982°C) 1 hour
  • Precipitation Treatment: 1325°F (718°C) 8 hours, Furnace Cool at 100°F (55°C) per hour to 1150°F (621°C) 8 hours

Inconel 718 Uses

Alloy 718 has many uses due to its excellent mechanical properties, such as high tensile strength, creep resistance, fatigue life, oxidation resistance and corrosion resistance. Some common applications include aircraft components such as landing gear parts; automotive components such as exhaust manifolds; medical devices such as screws for orthopaedic surgery; nuclear power plants; gas turbines; oil refineries; industrial valves; pressure vessels; heat exchangers; fasteners; bolts; nuts etc. Its heat resistance makes it an ideal material for any application involving elevated temperature operations like jet engines or combustion chambers in cars or motorcycles.

Corrosion Resistance

The high chromium content of Inconel 718 makes it highly resistant to corrosion from strong acids like hydrochloric acid or sulfuric acid at room temperature or elevated temperatures up to 1000°C (1800°F).

Heat Resistance

It also has excellent heat resistance, making it suitable for applications that involve very high temperatures, like jet engine components or combustion chambers in cars or motorcycles.

Heat Treatment

The main purpose of heat treatment is to obtain desired microstructure characteristics that are not achievable through conventional machining methods alone. It also helps improve the properties of the material by altering its hardness, strength, ductility etc., depending on the process used during the heat treatment process. Heat treatments used on Inconel 718 typically include solution annealing followed by ageing or precipitation hardening processes depending on the desired outcome from the heat treatment process, e.g., higher hardness levels achieved through precipitation hardening processes etc.


As far as machining goes, although grade 718 is difficult to machine due to its high work-hardening rate, with correct tool selection and cutting parameters, it can easily be machined into complex shapes with good surface finish quality being achieved after finishing operations like honing/polishing etc.


Welding can be done using several different welding processes like Gas Tungsten Arc Welding(GTAW), Plasma arc welding(PAW), Gas Metal Arc Welding(GMAW) etc., depending on the size/shape/location/thickness of the weld joint required for joining two pieces together using this material, e.g., GTAW would be preferred when welding thin sections. At the same time, GMAW would be suitable when welding thicker sections with larger weld beads, etc.


Inconel 718’s superior mechanical properties make it an indispensable material for many industries, including aerospace, automotive, medical, nuclear power plants, gas turbines, oil refineries, industrial valves, pressure vessels, fasteners, bolts, nuts etc. Its excellent heat resistance, combined with its corrosion resistance, makes it ideal for any application involving elevated temperatures, like jet engine components or combustion chambers. With correct tool selection & cutting parameters coupled with appropriate heat treatments applied according to desired outcomes from these processes, this material can easily be machined into complex shapes & welded together using various welding processes. Thus making this superalloy an integral part of any industry requiring materials that have superior performance qualities.

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