10 key points about Inconel 718

Double Sun
July 3, 2024
5:21 pm
530

Inconel 718 is a versatile nickel-chromium alloy notable for its high strength and exceptional resistance to environmental challenges in aerospace and other high-tech industries. Here is a structured exploration of its properties and applications:

inconel 718 physical properties

Property	Value
Density	8.19 g/cm³
Melting Point	1260-1340°C (2300-2440°F)
Thermal Conductivity	11.4 W/m·K at 200°C
Specific Heat Capacity	435 J/kg·K at 100°C
Thermal Expansion	13.0 µm/m·K at 20-100°C
Electrical Resistivity	1.25 µΩ·m at 20°C
Modulus of Elasticity	200 GPa (29,000 ksi)
Poisson’s Ratio	0.29
Tensile Strength	965 MPa (140,000 psi) minimum
Yield Strength (0.2% offset)	550 MPa (80,000 psi) minimum
Hardness	330 HB max (Brinell Hardness)
Elongation	12% minimum
Reduction of Area	17% minimum

inconel 718 composition

Nickel (Ni): Comprising 50-55% of the alloy, nickel provides high-temperature strength and excellent corrosion resistance, forming the base of Inconel 718.

Chromium (Cr): Making up 17-21% of the alloy, chromium enhances oxidation resistance and contributes significantly to the overall strength of the material.

Iron (Fe): Present as the balance of the composition, iron acts as a filler metal that stabilizes the alloy structure.

Niobium (Nb) and Tantalum (Ta): These elements constitute 4.75-5.5% of the alloy and are crucial for strengthening Inconel 718 through the formation of gamma prime (γ’) and gamma double prime (γ”) precipitates.

Molybdenum (Mo): At 2.8-3.3%, molybdenum increases both strength and corrosion resistance, particularly in reducing environments.

Titanium (Ti): With a content of 0.65-1.15%, titanium contributes to the formation of the gamma prime (γ’) phase, significantly increasing the alloy’s strength.

Aluminum (Al): Making up 0.2-0.8%, aluminum works with titanium to form the gamma prime (γ’) phase, which enhances the alloy’s strength.

Cobalt (Co): Present at a maximum of 1.0%, cobalt helps improve high-temperature strength and enhances corrosion resistance.

Carbon (C): At a maximum of 0.08%, carbon adds to the overall strength by forming carbides within the alloy.

Manganese (Mn): Present at a maximum of 0.35%, manganese acts as a deoxidizer and improves the alloy’s hot-working properties.

Silicon (Si): With a maximum of 0.35%, silicon serves as a deoxidizer and improves the castability of the alloy.

Phosphorus (P): Kept at a maximum of 0.015%, phosphorus is minimized to avoid embrittlement of the alloy.

Sulfur (S): Also kept at a maximum of 0.015%, sulfur is limited to prevent hot cracking and embrittlement.

Boron (B): Present at a maximum of 0.006%, boron enhances grain boundary strength, improving the alloy’s performance at high temperatures.

Copper (Cu): At a maximum of 0.3%, copper improves resistance to corrosion, especially in acidic environments.

Mechanical properties of inconel 718 at elevated temperatures

Ultimate Tensile Strength at 650°C (1200°F): 965 MPa (140 ksi)
Yield Strength at 650°C (1200°F): 760 MPa (110 ksi)
Elongation at 650°C (1200°F): 10-15%
Reduction of Area at 650°C (1200°F): 10-15%

inconel 718 density

Density: 8.19 g/cm³ (8190 kg/m³)

inconel 718 melting point

Melting Point: 1260-1340 °C (2300-2440 °F)

inconel 718 hardness

Brinell Hardness (HB): 330-370 HB
Rockwell Hardness (HRC): 44-47 HRC

inconel 718 yield strength

Yield Strength (0.2% Offset): 1030-1100 MPa (150-160 ksi)

inconel 718 thermal conductivity

Thermal Conductivity: 11.4 W/m·K at 21°C (70°F)

inconel 718 material properties can bring applications

Aerospace Components

Application: Gas turbine blades, compressor blades, and jet engine components.
Key Properties:
- High-Temperature Strength: Inconel 718 maintains its strength at temperatures up to 700°C (1292°F), making it ideal for high-stress turbine and engine parts.
- Oxidation Resistance: Excellent resistance to oxidation at high temperatures ensures longevity and reliability in aerospace environments.

2. Rocket Engines

Application: Components such as rocket motor casings and combustion chambers.
Key Properties:
- High Strength-to-Weight Ratio: Ensures structural integrity while keeping the weight low, crucial for aerospace applications.
- Creep Resistance: Ability to withstand deformation under high temperature and stress over time.

3. Nuclear Reactors

Application: Reactor core components and control rod mechanisms.
Key Properties:
- Corrosion Resistance: Exceptional resistance to a wide range of corrosive environments, including radiation and high temperatures found in nuclear reactors.
- Radiation Resistance: Maintains mechanical properties even under intense radiation.

4. Oil and Gas Industry

Application: Downhole shafts, wellhead components, and tubing.
Key Properties:
- Corrosion Resistance: Excellent resistance to hydrogen sulfide and other corrosive chemicals found in oil and gas extraction.
- High Strength: Capable of withstanding high pressure and mechanical stresses encountered during drilling and extraction.

5. Chemical Processing

Application: Heat exchangers, reaction vessels, and piping.
Key Properties:
- Corrosion Resistance: Withstands harsh chemical environments, including acids and alkalis.
- High Strength: Ensures durability and reliability in equipment exposed to extreme chemical conditions.

6. Cryogenic Applications

Application: Storage tanks and cryogenic piping systems.
Key Properties:
- Maintains Toughness at Low Temperatures: Inconel 718 retains excellent mechanical properties at cryogenic temperatures, making it suitable for ultra-low temperature applications.

7. Marine Applications

Application: Marine fasteners, springs, and other components exposed to seawater.
Key Properties:
- Corrosion Resistance: Highly resistant to seawater corrosion and biofouling.
- Fatigue Resistance: Withstands cyclic loading and mechanical stresses common in marine environments.

Summary

The unique combination of high-temperature strength, corrosion resistance, and excellent mechanical properties makes Inconel 718 an ideal material for various demanding applications. Its ability to perform reliably in extreme conditions, from the high temperatures of aerospace engines to the corrosive environments of chemical processing and the low temperatures of cryogenic storage, underscores its versatility and robustness.

Common forms of inconel 718

Inconel 718 Sheets and Plates: Used in the aerospace industry for making structural components.
Inconel 718 Bars and Rods: Used for manufacturing high-strength fasteners, bolts, and other hardware.
Inconel 718 Wires: Utilized in applications requiring high strength and corrosion resistance, such as springs and electrical components.
Inconel 718 Tubes and Pipes: Used in the chemical processing and oil & gas industries for handling corrosive fluids at high temperatures.
Inconel 718 Forgings: Custom shapes and sizes for specific high-performance components in aerospace, marine, and industrial applications.