Overview
Inconel 718 is a precipitation-hardenable nickel-chromium superalloy renowned for its exceptional high strength, fatigue resistance, creep resistance, oxidation resistance, and corrosion resistance across a wide temperature range.
Developed for demanding aerospace and energy applications, Inconel 718 maintains excellent mechanical properties from cryogenic temperatures up to approximately 700°C (1290°F). The alloy achieves its outstanding strength through precipitation hardening from niobium and titanium additions.
Inconel 718 is widely used in:
- Aerospace Engine Components
- Gas Turbines
- Rocket Engines
- Oil & Gas Equipment
- Nuclear Systems
- High-Temperature Fasteners
- Power Generation Equipment
- Industrial Turbomachinery
Due to its unique combination of strength, corrosion resistance, and manufacturability, Inconel 718 is one of the most widely used nickel-based superalloys in the world.
Material Specification
| Property | Value |
|---|---|
| Material Designation | Inconel 718 |
| UNS Number | N07718 |
| Werkstoff Number | 2.4668 |
| ASTM Standards | ASTM B637, B670, B906 |
| Material Family | Precipitation-Hardened Nickel Superalloy |
| Density | 8.19 g/cm³ |
| Magnetic Property | Slightly Magnetic |
| Typical Supply Condition | Solution Annealed / Aged |
| Standard Forms | Plate, Sheet, Bar, Rod, Tube, Pipe, Wire, Forgings |
Chemical Composition
| Element | Content (%) |
|---|---|
| Nickel (Ni) | 50.0–55.0 |
| Chromium (Cr) | 17.0–21.0 |
| Iron (Fe) | Balance |
| Niobium + Tantalum (Nb+Ta) | 4.75–5.50 |
| Molybdenum (Mo) | 2.80–3.30 |
| Titanium (Ti) | 0.65–1.15 |
| Aluminum (Al) | 0.20–0.80 |
| Cobalt (Co) | ≤1.00 |
| Carbon (C) | ≤0.08 |
| Manganese (Mn) | ≤0.35 |
| Silicon (Si) | ≤0.35 |
The combination of niobium, titanium, and aluminum enables precipitation hardening, resulting in exceptional strength and creep resistance.
Mechanical Properties
Solution Annealed and Aged Condition
| Property | Value |
|---|---|
| Tensile Strength | ≥1240 MPa |
| Yield Strength (0.2%) | ≥1035 MPa |
| Elongation | ≥12% |
| Hardness | 330–450 HB |
| Elastic Modulus | 200 GPa |
Typical Mechanical Performance
| Property | Value |
|---|---|
| Fatigue Resistance | Outstanding |
| Impact Toughness | Excellent |
| Creep Resistance | Outstanding |
| Fracture Toughness | Excellent |
Physical Properties
| Property | Value |
|---|---|
| Density | 8.19 g/cm³ |
| Melting Range | 1260–1336°C |
| Thermal Conductivity | 11.4 W/m·K |
| Electrical Conductivity | 1.3% IACS |
| Electrical Resistivity | 1.25 μΩ·m |
| Thermal Expansion Coefficient | 13.0 × 10⁻⁶/K |
| Specific Heat Capacity | 435 J/kg·K |
High Temperature Performance
| Property | Performance |
|---|---|
| Creep Resistance | Outstanding |
| Stress Rupture Resistance | Outstanding |
| Oxidation Resistance | Excellent |
| Service Temperature | Up to 700°C |
Inconel 718 is specifically designed for long-term service under high stress at elevated temperatures.
Strength-to-Weight Ratio
| Material | Density (g/cm³) | Tensile Strength |
|---|---|---|
| Inconel 718 | 8.19 | 1240 MPa |
| Inconel 625 | 8.44 | 827 MPa |
| Inconel 600 | 8.47 | 550 MPa |
| Titanium Grade 5 | 4.43 | 895 MPa |
Inconel 718 offers one of the highest strength levels among commercially available nickel superalloys.
Corrosion Resistance
| Environment | Performance |
|---|---|
| Fresh Water | Excellent |
| Seawater | Excellent |
| Chloride Solutions | Excellent |
| Oxidizing Acids | Excellent |
| Organic Acids | Excellent |
| Industrial Atmospheres | Excellent |
Inconel 718 provides excellent resistance to:
- Pitting Corrosion
- Crevice Corrosion
- Stress Corrosion Cracking
- Oxidation
- Sulfidation
Recommended surface treatments:
- Pickling
- Passivation
- Electropolishing
- Mechanical Polishing
Oxidation Resistance
| Temperature Range | Performance |
|---|---|
| Up to 650°C | Outstanding |
| 650–700°C | Excellent |
| Above 700°C | Good |
A protective chromium oxide layer provides long-term oxidation resistance.
Fatigue Resistance
| Property | Performance |
|---|---|
| High-Cycle Fatigue | Outstanding |
| Low-Cycle Fatigue | Outstanding |
| Thermal Fatigue | Excellent |
| Cyclic Stress Resistance | Outstanding |
These properties make Inconel 718 one of the most commonly used aerospace engine alloys.
Weldability
| Welding Process | Rating |
|---|---|
| TIG Welding | Excellent |
| MIG Welding | Excellent |
| Resistance Welding | Excellent |
| Laser Welding | Excellent |
Compared with many precipitation-hardened superalloys, Inconel 718 offers excellent weldability.
Machinability
| Process | Rating |
|---|---|
| CNC Turning | Difficult |
| CNC Milling | Difficult |
| Drilling | Difficult |
| Grinding | Good |
| EDM Machining | Excellent |
Machinability Comparison
| Material | Machinability |
|---|---|
| Aluminum 6061 | Excellent |
| 316 Stainless Steel | Good |
| Inconel 625 | Moderate |
| Inconel 718 | Difficult |
High strength and severe work hardening require rigid tooling and optimized machining strategies.
Heat Treatment
Solution Annealing
| Parameter | Value |
|---|---|
| Temperature | 925–980°C |
| Cooling Method | Air Cool |
Double Aging Treatment
| Parameter | Value |
|---|---|
| First Aging | 718°C for 8 Hours |
| Controlled Cooling | 55°C/hour |
| Second Aging | 621°C for 8 Hours |
| Cooling Method | Air Cool |
Heat Treatability
| Property | Performance |
|---|---|
| Precipitation Hardening | Outstanding |
| Structural Stability | Excellent |
| High-Temperature Strength Retention | Outstanding |
The aging process is critical for achieving maximum mechanical performance.
International Equivalent Grades
| Standard | Equivalent Grade |
|---|---|
| UNS | N07718 |
| ASTM | Inconel 718 |
| DIN | 2.4668 |
| EN | NiCr19Fe19NbMo3 |
| ISO | NiCr19Fe19NbMo3 |
| JIS | NCF718 |
| GB/T (China) | GH4169 |
Available Forms
| Product Type | Availability |
|---|---|
| Plate | Yes |
| Sheet | Yes |
| Round Bar | Yes |
| Pipe | Yes |
| Tube | Yes |
| Wire | Yes |
| Forgings | Yes |
Typical Applications
Aerospace Industry
- Turbine Discs
- Compressor Components
- Engine Shafts
- Fasteners
- Jet Engine Parts
Space Industry
- Rocket Engines
- Cryogenic Tanks
- Launch Vehicle Components
Oil & Gas Industry
- Wellhead Equipment
- Downhole Tools
- Subsea Fasteners
- High-Pressure Valves
Power Generation
- Gas Turbine Components
- Turbine Blades
- Combustion Systems
Nuclear Industry
- Reactor Components
- High-Temperature Fasteners
- Structural Systems
Industrial Applications
- High-Strength Bolts
- Springs
- Pressure Vessels
- Heat-Resistant Components
Manufacturing Characteristics
| Manufacturing Process | Rating |
|---|---|
| CNC Machining | Moderate to Difficult |
| Welding | Excellent |
| Forging | Excellent |
| Heat Treatment | Critical |
| Forming | Good |
Advantages
Exceptional Strength
One of the strongest commercially available nickel superalloys.
Outstanding Fatigue Resistance
Ideal for cyclic loading and aerospace applications.
Excellent High-Temperature Performance
Maintains strength and creep resistance up to approximately 700°C.
Good Corrosion Resistance
Suitable for aggressive industrial environments.
Excellent Weldability
Superior to many other precipitation-hardened superalloys.
Proven Aerospace Performance
Widely used in aircraft and space systems.
Limitations
Difficult Machining
High hardness and work hardening increase manufacturing complexity.
High Material Cost
More expensive than stainless steels and many nickel alloys.
Heavy Material
Higher density than titanium alloys.
Temperature Limit Below Some Superalloys
For continuous service above 700°C, other alloys may be preferred.
Comparison with Other Nickel Alloys
| Property | Inconel 718 | Inconel 625 | Inconel 600 |
|---|---|---|---|
| Strength | Highest | High | Moderate |
| Corrosion Resistance | Excellent | Outstanding | Excellent |
| Creep Resistance | Outstanding | Excellent | Good |
| Weldability | Excellent | Outstanding | Excellent |
| Heat Treatable | Yes | No | No |
Comparison with Common Engineering Materials
| Material | Density | Tensile Strength | Service Temperature |
|---|---|---|---|
| Inconel 718 | 8.19 g/cm³ | 1240 MPa | 700°C |
| Inconel 625 | 8.44 g/cm³ | 827 MPa | 980°C |
| Titanium Grade 5 | 4.43 g/cm³ | 895 MPa | 400°C |
| 316L Stainless Steel | 8.00 g/cm³ | 485 MPa | 870°C |
Available Surface Finishes
Raw Finishes
- Mill Finish
- Annealed Finish
- Pickled Finish
Functional Finishes
- Precision Machined Finish
- Ground Finish
- Polished Finish
Specialty Finishes
- Electropolished Finish
- Passivated Finish
- Aerospace Grade Finish
Frequently Asked Questions (FAQ)
What is Inconel 718?
Inconel 718 is a precipitation-hardened nickel-based superalloy designed for high-strength and high-temperature applications.
What is Inconel 718 used for?
Typical applications include:
- Aerospace Engine Components
- Turbine Discs
- Rocket Engines
- Oil & Gas Equipment
- Power Generation Systems
What is the equivalent material to Inconel 718?
Common equivalents include:
- UNS N07718
- DIN 2.4668
- GH4169
- NiCr19Fe19NbMo3
What is the difference between Inconel 718 and Inconel 625?
| Property | Inconel 718 | Inconel 625 |
|---|---|---|
| Strength | Much Higher | Lower |
| Heat Treatable | Yes | No |
| Creep Resistance | Better | Good |
| Corrosion Resistance | Excellent | Outstanding |
Is Inconel 718 corrosion resistant?
Yes. It offers excellent resistance to oxidation, pitting, crevice corrosion, and industrial environments.
Can Inconel 718 be welded?
Yes. It has better weldability than many precipitation-hardened nickel superalloys.
Why choose Inconel 718?
Because it combines:
- Exceptional Strength
- Outstanding Fatigue Resistance
- Excellent High-Temperature Stability
- Good Corrosion Resistance
- Aerospace-Proven Reliability
Is Inconel 718 suitable for aerospace applications?
Yes. It is one of the most widely used aerospace superalloys in turbine engines and structural components.
Does GCNOV provide custom manufacturing services for Inconel 718?
Yes. GCNOV provides:
- CNC Machining
- Precision Turning and Milling
- Nickel Superalloy Fabrication
- Heat Treatment Support
- Surface Finishing
- Prototype Development
- Low-Volume Production
- Mass Production