Inconel 718 Alloys (UNS N07718)

Products

Inconel 718 (ASTM B637, AMS 5662, AMS 5663)

Inconel 718 sheets are nickel-chromium-molybdenum alloys. They resist corrosion, pitting, and oxidation in harsh environments. The alloy stays strong and stable at high temperatures. It shows excellent tensile, yield, and creep-rupture strength. It performs well under heat and pressure. Inconel 718 also offers great corrosion resistance. It is easy to form, weld, and machine. Supreme Engineering Limited is one of the top Inconel 718 suppliers and manufacturers in India.

The alloy welds easily and resists post-weld cracking. It can be fabricated quickly and at a low cost. It combines high tensile, fatigue, and rupture strength. These features make it durable and reliable. Inconel 718 works well in aerospace, chemical, marine, and power industries. It is used in turbine discs, rocket casings, rings, and engine components. It performs well in aircraft and land-based gas turbines. Inconel 718 sheets deliver strength, endurance, and corrosion resistance in the toughest conditions.

Key Properties

Inconel 718 is a nickel-chromium-molybdenum alloy. It is strong, corrosion-resistant, and stable under heat and pressure. Below are its main properties explained clearly and simply.

1. High Strength

Inconel 718 has very high strength. It keeps this strength at temperatures up to 700°C (1290°F). It works well in engines, turbines, and high-stress parts. The alloy stays strong during long use under heavy loads.

2. Excellent Corrosion Resistance

The alloy fights corrosion in tough environments. It resists oxidation, pitting, crevice corrosion, and cracking. It performs well in both oxidizing and reducing atmospheres. This makes it ideal for marine and chemical industries.

3. Great Weldability

Inconel 718 welds easily. It resists post-weld cracking and needs little preheat or post-treatment. It works well with TIG, MIG, and stick welding. This helps reduce time and cost during fabrication.

4. Strong Creep and Fatigue Resistance

The alloy keeps its creep and fatigue strength during long service at high temperatures. It works well in rotating parts like turbine blades, rotors, and gas engines.

5. Easy Forming and Machining

You can form and machine Inconel 718 without much trouble. It can be hot-formed or cold-formed. It machines well in the annealed condition when using proper tools and cutting speeds.

6. Heat and Oxidation Resistance

The alloy stands strong in high heat and oxidizing environments. It forms a stable oxide layer that protects its surface. It does not scale or lose strength under heat.

7. Stable Structure

Its gamma prime and gamma double prime phases give it a stable microstructure. This stability helps it perform well even after long exposure to heat or pressure.

8. Non-Magnetic

Inconel 718 is non-magnetic in all conditions. It stays stable even after heat treatment or cold working. It suits tools and parts that must not attract magnetic fields

9. Works in Cryogenic Conditions

The alloy stays tough and ductile at very low temperatures. It is often used in space and aerospace parts that face both extreme heat and cold.

10. Long Service Life

Inconel 718 lasts long with low maintenance. Its strength and corrosion resistance reduce part failures. It saves time and cost over long operations.

Inconel 718 offers high strength, great weldability, corrosion protection, and heat resistance. It performs under pressure and lasts long. These traits make it ideal for aerospace, marine, chemical, and power industries.

Performance Profile:

Inconel 718 is a strong nickel-chromium-molybdenum alloy. It shows high strength, corrosion resistance, and stability at high temperatures. This alloy performs well in harsh environments like jet engines, turbines, and oil and gas systems. It offers long life, easy fabrication, and great reliability under stress.

1. Mechanical Strength

Inconel 718 has very high tensile and yield strength. It keeps its form and power at temperatures up to 700°C (1300°F). Niobium and molybdenum give it strong resistance to stress and deformation.

2. High-Temperature Performance

The alloy stays strong when heated. It resists oxidation, scaling, and fatigue at high temperatures. It keeps its shape even during long exposure to heat. These features make it perfect for gas turbines, rocket engines, and aircraft parts.

3. Corrosion and Oxidation Resistance

Inconel 718 resists attack from acids and harsh chemicals.

4. Fabrication and Machinability

The alloy is easy to form, weld, and machine. It does not crack after welding. You can forge or heat-treat it without much distortion. Its good workability helps reduce cost and time during production.

5. Fatigue and Creep Resistance

Inconel 718 handles stress and heat cycles very well. It resists creep, rupture, and fatigue even after long use. Its stable structure helps it last longer in turbine blades, compressor parts, and fasteners.

6. Thermal Stability and Conductivity

The alloy shows low heat transfer and high thermal stability. It resists sudden temperature changes. It stays reliable in engines and heat exchangers that face frequent heating and cooling.

7. Cryogenic Properties

Inconel 718 stays tough even at very low temperatures. It works well down to −253°C, making it suitable for cryogenic tanks, rockets, and space tools.

8. Magnetic and Electrical Properties

This alloy is non-magnetic and stable. It keeps steady electrical resistance even when heated. These features make it useful for high-stress electrical systems.

9. Wear and Erosion Resistance

Its hard surface protects against friction, wear, and erosion. The oxide layer helps prevent damage. It performs well in high-speed and high-pressure systems, giving longer service life.

10. Applications Summary

Inconel 718 is used in many industries:

Aerospace: Turbine blades, engine parts, and discs
Energy: Reactor parts and gas turbines
Oil & Gas: Valves and drilling tools
Chemical Plants: Heat exchangers and vessels
Space: Rocket casings and cryogenic systems

Inconel 718 is strong, durable, and easy to work with. It offers high strength, corrosion resistance, and thermal stability. Its balanced features make it ideal for critical and high-performance uses across industries.

Common Applications

Inconel 718 is a strong, corrosion-resistant alloy made from nickel, chromium, and molybdenum. It performs well in heat, pressure, and harsh conditions. Because of these features, it is used in many key industries.

1. Aerospace Industry

Aerospace uses Inconel 718 for its strength and heat resistance. It stays stable under high stress and temperature. Applications include:

2. Gas Turbine and Power Generation

Aerospace uses Inconel 718 for its strength and heat resistance. It stays stable under high stress and temperature. Applications include:

3. Oil and Gas Industry

The alloy resists corrosion, sour gas, and high pressure. It works well in deep drilling and harsh offshore sites. Applications include:

4. Marine and Offshore Engineering

Inconel 718 resists saltwater and keeps strength under pressure. It ensures safe operation in marine setups. Applications include:

5. Chemical and Industrial Plants

The alloy resists acids, alkalis, and oxidizing chemicals. It lasts long in chemical plants and reactors. Applications include:

6. Automotive and Racing

Inconel 718 handles extreme heat and stress in vehicles. It supports performance and durability. Applications include:

7. Nuclear Industry

The alloy endures high pressure, radiation, and heat in nuclear systems. It helps ensure safe operation. Applications include:

8. Tooling and Manufacturing

Inconel 718 stays tough under friction and heat. It is used in heavy manufacturing tools. Applications include:

Inconel 718 stands out for strength, corrosion resistance, and heat stability. It works well in aerospace, energy, marine, and industrial systems. Its reliability makes it a top choice for engineers worldwide.

Specifications:

Inconel 718
Alloy 718
UNS N07718
W.Nr. 2.4668
ASTM B670 (Sheets, Plates, and Strips)
ASTM B637 (Bars, Forgings, and Forging Stock)
ASTM B906 (Seamless and Welded Tubing)
AMS 5596 (Sheet, Strip, and Plate)
AMS 5662 (Bars, Forgings, and Rings – Solution Heat Treated)
AMS 5663 (Bars, Forgings, and Rings – Precipitation Heat Treated)
AMS 5664 (Bars and Forgings – Hot Worked)
BS 3076 NA 51
DIN 17744
ISO 15156 / NACE MR0175
EN 2.4668

Chemical Composition (WT %):

Element	Symbol	Weight % (wt%) — Typical / Limits	Role / Effect on alloy	Notes / Standard limits
Nickel	Ni	50.0 – 55.0 (balance)	Main matrix. Gives corrosion resistance and high-temperature strength.	Nickel forms the base. Most of the alloy is Ni.
Chromium	Cr	17.0 – 21.0	Provides oxidation and corrosion resistance. Helps form a protective oxide.	Key for corrosion and scale resistance.
Iron	Fe	Remainder / balance (typically ~17–21 when Ni lower)	Fills matrix. Affects toughness and cost.	Often listed as “balance” in specs. Actual Fe depends on Ni content. (Continental Steel & Tube Company)
Niobium (Columbium) + Tantalum	Nb (Cb) + Ta	4.75 – 5.50 (Nb mainly; Ta trace)	Promotes γ″ precipitates. Drives age-hardening and high strength.	Nb (often shown as Cb) is the γ″ former. Ta is usually ≤0.05%. (AZoM)
Molybdenum	Mo	2.80 – 3.30	Adds solid-solution strength. Improves creep and pitting resistance.	Contributes to high-temperature strength. (specialmetals.com)
Titanium	Ti	0.65 – 1.15	Helps form γ′ and γ″ phases with Al. Aids age-hardening.	Balance of Ti controls precipitation kinetics. (AZoM)
Aluminium	Al	0.20 – 0.80	Works with Ti to form strengthening precipitates (γ′).	Small but critical for precipitation strengthening.
Carbon	C	≤ 0.08 (max)	Affects carbide formation. Influences creep and fracture behavior.	Kept low to avoid excessive carbides. (AZoM)
Manganese	Mn	≤ 0.35 (max)	Deoxidizer and impurity control. Minor solid-solution effect.	Controlled for cleanliness and toughness. (AZoM)
Silicon	Si	≤ 0.35 (max)	Deoxidizer. Small effect on strength.	Kept low to avoid embrittlement. (AZoM)
Phosphorus	P	≤ 0.015 (max)	Impurity. High levels harm toughness.	Strictly limited per specs. (AZoM)
Sulfur	S	≤ 0.015 (max)	Impurity. Promotes hot cracking and reduced ductility.	Kept very low. (AZoM)
Cobalt	Co	≤ 1.00 (max)	Minor strengthening. Sometimes present from raw materials.	Limited to control cost and property balance. (AZoM)
Boron	B	≤ 0.006 (max)	Grain boundary strengthener in tiny amounts.	Very small addition; helps creep strength if controlled. (AZoM)
Copper	Cu	≤ 0.30 (max)	Impurity; small effect on corrosion.	Limited in most specs. (AZoM)
Tantalum (trace)	Ta	≤ 0.05 (max)	Often reported with Nb. Minor role in precipitation.	Usually included in the Nb+Ta total. (AZoM)

Physical Properties:

Property	Metric Value	Imperial Value	Description / Remarks
Density	8.19 g/cm³	0.296 lb/in³	Indicates the compactness of the alloy. High density supports strength and durability in aerospace and industrial applications.
Melting Point	1260 – 1336 °C	2300 – 2440 °F	The alloy retains strength and resists deformation at high temperatures. Ideal for turbine and engine components.
Specific Heat Capacity	435 J/kg·K	0.104 BTU/lb·°F	Represents the heat required to raise the temperature by one degree. Shows good thermal stability.
Thermal Conductivity (at 100°C)	11.4 W/m·K	78.9 BTU·in/hr·ft²·°F	Measures heat transfer ability. Inconel 718 has moderate thermal conductivity, reducing heat loss under load.
Electrical Resistivity (at 20°C)	1.29 × 10⁻⁶ Ω·m	50.8 µΩ·in	Shows strong resistance to electric current, suitable for high-temperature electrical systems.
Elastic Modulus (Tensile Modulus)	200 GPa	29 × 10⁶ psi	Reflects the stiffness of the alloy. It resists deformation under tension and compression.
Poisson’s Ratio	0.29	0.29	Describes the ratio of lateral strain to axial strain under stress. Ensures good ductility.
Coefficient of Thermal Expansion (20–100°C)	13.0 µm/m·°C	7.2 µin/in·°F	Indicates how much the alloy expands when heated. Stable and predictable under thermal cycling.
Hardness (Rockwell C)	36 – 45 HRC	36 – 45 HRC	Represents the material’s surface resistance to indentation. The hardness depends on heat treatment.
Modulus of Rigidity (Shear Modulus)	77 GPa	11.2 × 10⁶ psi	Measures the alloy’s ability to resist shear deformation. Ensures high load-bearing performance.
Young’s Modulus	205 GPa	29.7 × 10⁶ psi	Confirms the excellent elasticity and rigidity of the alloy under stress.
Thermal Expansion (100–500°C)	13.3 µm/m·°C	7.4 µin/in·°F	Low thermal expansion rate enhances dimensional stability during heat exposure.
Magnetic Permeability (at 200 Oersted)	1.002 max	1.002 max	Inconel 718 is nearly non-magnetic even after cold working or heat treatment.
Modulus of Resilience	1.23 × 10⁶ J/m³	0.18 × 10⁶ psi	Reflects the energy the alloy can absorb without permanent deformation.
Thermal Diffusivity (at 100°C)	2.8 mm²/s	0.0043 in²/s	Represents the rate of heat spread through the alloy’s structure.
Density at Room Temperature	8190 kg/m³	0.296 lb/in³	Indicates consistent material mass per volume, suitable for heavy-duty use.
Maximum Service Temperature (Oxidizing Atmosphere)	700 °C	1292 °F	The highest temperature at which the alloy maintains its mechanical and chemical properties.
Specific Gravity	8.19	8.19	Ratio of density compared to water. Shows the compactness and strength of the alloy.

Mechanical Properties

Property	Metric	Imperial	Condition / Notes
Density	8.19 g/cm³	0.296 lb/in³	At 20°C
Melting Point	1260–1336°C	2300–2440°F	—
Tensile Strength (Ultimate)	1240 MPa	180 ksi	Annealed + Aged
Yield Strength (0.2% Offset)	1035 MPa	150 ksi	Annealed + Aged
Elongation at Break	12–25 %	12–25 %	Depends on condition
Hardness (Rockwell C)	33–44 HRC	33–44 HRC	Aged condition
Elastic Modulus	205 GPa	29.7 × 10³ ksi	Room temperature
Poisson’s Ratio	0.29	0.29	—
Shear Modulus	77.2 GPa	11.2 × 10³ ksi	—
Fatigue Strength	510 MPa	74 ksi	10⁷ cycles, aged
Creep Rupture Strength (at 650°C for 1000 hr)	655 MPa	95 ksi	—
Fracture Toughness (K_IC)	120 MPa√m	109 ksi√in	Aged condition
Impact Strength (Charpy V-Notch)	170 J	125 ft-lb	Room temperature
Thermal Conductivity	11.4 W/m·K	78.8 BTU·in/hr·ft²·°F	At 21°C
Specific Heat Capacity	435 J/kg·K	0.104 BTU/lb·°F	At 21°C
Thermal Expansion Coefficient	13.0 µm/m·°C	7.2 µin/in·°F	20–100°C range
Electrical Resistivity	125 µΩ·cm	49.2 µΩ·in	At 20°C
Modulus of Rigidity	81.7 GPa	11.9 × 10³ ksi	—
Service Temperature Range	-253°C to 704°C	-423°F to 1300°F	Typical operating range
Magnetic Permeability	1.0006 max	1.0006 max	Non-magnetic in annealed condition
Machinability Rating	15–20% (of B1112 steel)	—	Difficult to machine due to hardness
Formability	Good	Good	Hot and cold workable
Weldability	Excellent	Excellent	Resistant to post-weld cracking
Creep Resistance	Very High	Very High	Retains strength at high temperature
Oxidation Resistance	Excellent	Excellent	Up to 980°C (1800°F)

Heat treatment:

Heat Treatment Stage	Temperature Range (°C / °F)	Holding Time	Cooling Method	Purpose / Effect
Solution Annealing (Standard Anneal)	980–1010°C / 1800–1850°F	1–2 hours	Air Cool or Faster	Dissolves precipitated phases and homogenizes structure. Prepares alloy for aging.
Solution Annealing (Alternate High-Strength Anneal)	940–955°C / 1725–1750°F	1–1.5 hours	Air Cool	Produces slightly higher strength and lower ductility. Used when greater hardness is required.
Stabilization Treatment (Optional)	760–870°C / 1400–1600°F	1–4 hours	Air Cool	Stabilizes microstructure before aging. Helps prevent distortion and improves uniformity.
Double Aging – Step 1 (Primary Age Hardening)	720°C / 1325°F	8 hours	Furnace Cool to 620°C / 1150°F at 50°F (28°C) per hour	Promotes precipitation of γ” (gamma double prime) and γ’ (gamma prime) phases, which increase strength.
Double Aging – Step 2 (Secondary Age Hardening)	620°C / 1150°F	8 hours	Air Cool	Completes precipitation process and develops final mechanical properties. Maximizes creep and rupture strength.
Stress Relieving (Optional)	870°C / 1600°F	1 hour	Air Cool	Reduces residual stresses after cold work or machining. Prevents cracking during service.
Precipitation Hardening (Direct Aging from Solution)	720°C → 620°C / 1325°F → 1150°F	8 hours at 720°C, then furnace cool at 50°F/hr to 620°C and hold for 8 hours	Air Cool	Develops full hardness and tensile strength in one continuous cycle. Common industrial practice.
Weld Heat Treatment (Post-Weld Anneal + Aging)	980°C / 1800°F followed by aging cycle (720°C/8hr → 620°C/8hr)	Variable	Air Cool	Restores ductility and strength lost in welding. Reduces risk of post-weld cracking.

Frequently Asked Questions (FAQs)

What is Inconel 718 and what makes it special?

Inconel 718 is a nickel-chromium-molybdenum alloy. It stays strong in extreme heat and resists corrosion. The alloy works well up to 700°C (1290°F). It fights oxidation, pitting, and crevice damage. It is tough, easy to weld, and ideal for high-stress use in aerospace, marine, and power plants.

What are the main applications of Inconel 718?

Industries use Inconel 718 where high strength and heat resistance are needed. It is common in jet engines, gas turbines, rocket parts, and exhaust systems. It is also used in compressor discs, nuclear reactors, and drilling tools. Its long life and corrosion resistance make it reliable for heavy-duty work.

How does Inconel 718 perform during welding and fabrication?

Inconel 718 welds easily and resists cracking. It can be formed, forged, and machined with the right tools. The alloy keeps its strength after welding and heat treatment. Its stable structure helps in making complex parts. This makes it a favorite for aerospace and engineering industries.

What are the mechanical properties of Inconel 718?

Inconel 718 has high tensile and yield strength. It also resists fatigue and creep at high temperatures. Its tensile strength reaches about 1350 MPa. The alloy stays stable under pressure for long periods. These traits make it safe and dependable for critical uses.

How does Inconel 718 compare with other Inconel grades?

Inconel 718 is stronger and easier to weld than Inconel 600 or 625. It performs better in high-stress and high-heat areas. Inconel 625 focuses more on corrosion resistance. Inconel 718 offers both strength and workability. That is why aerospace and turbine makers prefer it for demanding jobs.