Inconel 718 Flanges
Inconel 718 Flanges
Specification
- Standard: ASTM B564, ASME SB564
- Grade: Inconel 718 (UNS N07718)
- Form: Flanges (Slip-on Flange, Weld Neck Flange, Blind Flange, Socket Weld Flange, Threaded Flange, Lap Joint Flange, Plate Flange)
- Size: Available in various dimensions (½”, ¾”, 1”, 1 ¼”, 1 ½”, 2”, 2 ½”, 3”, 4”, 5”, 6”, 8”, 10”, 12”, 14”, 16”, 18”, 20”, 24”, 26”, 28”, 30”, 32”, 34”, 36”, 38”, 40”, 42”, 44”, 46”, 48”)
- Pressure Class: 150, 300, 600, 800, 900, 1500, 2500
- End Types: Flanged, Threaded, Welded
Inconel 718 Chemical Composition
| Element | % Composition (Nominal) |
|---|---|
| Nickel (Ni) | 50-55% |
| Chromium (Cr) | 17.0-21.0% |
| Iron (Fe) | Balance |
| Molybdenum (Mo) | 2.8-3.3% |
| Cobalt (Co) | 1.0% max |
| Aluminum (Al) | 0.2-0.8% |
| Titanium (Ti) | 0.7-1.2% |
| Manganese (Mn) | 0.35% max |
| Silicon (Si) | 0.35% max |
| Carbon (C) | 0.08% max |
Inconel 718 Mechanical Properties:
| Property | Value |
|---|---|
| Tensile Strength | 140,000 – 180,000 psi (965 – 1240 MPa) |
| Yield Strength | 70,000 – 110,000 psi (485 – 758 MPa) |
| Elongation at Break | 15 – 25% |
| Hardness (Rockwell C) | 35-42 |
| Modulus of Elasticity | 27,000 ksi (186,000 MPa) |
Inconel 718 Physical Properties
| Property | Value |
|---|---|
| Density | 8.19 g/cm³ |
| Melting Point | 1260°C – 1335°C |
| Electrical Resistivity | 1.10 x 10⁻⁶ Ω·m |
| Thermal Conductivity | 10.8 W/m·K |
| Coefficient of Thermal Expansion | 13.0 µm/m·K (20°C – 100°C) |
Possible Alternative Grades:
| Grade | Description |
|---|---|
| Inconel 625 (UNS N06625) | Superior weldability, better resistance to oxidation at higher temperatures. |
| Incoloy 800 (UNS N08800) | Excellent oxidation and corrosion resistance, lower temperature resistance compared to 718. |
| Haynes 230 (UNS N06230) | Offers higher creep resistance and improved high-temperature stability. |
Chemical Formula:
The chemical formula for Inconel 718 is: Ni₅₀Cr₂₀Fe₁₈Mo₃Al₀.8Ti₁.0
Grade Specification Comparison:
| Property | Inconel 718 | Inconel 625 | Incoloy 800 |
|---|---|---|---|
| Maximum Service Temp | 1300°F (704°C) | 2200°F (1204°C) | 1500°F (816°C) |
| Corrosion Resistance | Excellent | Excellent | Good |
| Oxidation Resistance | Excellent | Excellent | Fair |
| Creep Strength | High | Moderate | Good |
| Weldability | Good | Excellent | Moderate |
Corrosion Resistance:
Inconel 718 flanges have excellent resistance to a wide variety of aggressive environments, including acids, alkalis, and seawater. Its chromium content provides superior resistance to oxidation and corrosion, especially in high-temperature conditions. The alloy’s performance in sulfur-bearing environments and acidic solutions makes it a preferred choice for harsh applications.
Heat Resistance:
Inconel 718 is specifically designed to perform at high temperatures, making it an ideal material for components that experience continuous service at temperatures up to 1300°F (704°C). It maintains its strength and oxidation resistance, even under extreme conditions, allowing it to endure high-temperature environments such as those found in gas turbines, jet engines, and high-temperature reactors.
Heat Treatment:
Inconel 718 flanges undergo a precipitation hardening heat treatment, which improves their strength, toughness, and overall mechanical properties. The process typically involves the following stages:
- Solution Annealing: Heat the material to 1700°F (926°C) for one hour.
- Aging: Heat to 1325°F (718°C) for 8 hours, followed by air cooling.
- Final Aging: Heat to 1150°F (621°C) for 8 hours to optimize the mechanical properties.
Welding:
Inconel 718 flanges can be welded using a variety of methods, including gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW). To ensure high-quality welds, preheating and post-weld heat treatments are recommended. Proper welding procedures help avoid cracking and maintain the material’s mechanical properties.
Fabrication:
Inconel 718 is known for its excellent machinability, despite being a high-strength material. It is important to use proper tooling and machining parameters, as the alloy can work-harden quickly. Common fabrication techniques include:
- Cutting: Plasma cutting, laser cutting, and water jet cutting.
- Forming: Forging, bending, and rolling are possible, though care must be taken due to the material’s strength.
- Finishing: Polishing and coating options are available to enhance corrosion resistance.
Applications:
Inconel 718 flanges are commonly used in the following industries and applications:
- Aerospace: Aircraft engines, gas turbines, rocket engines, and heat exchangers.
- Power Generation: Turbines, compressors, and reactors.
- Chemical Processing: Valves, pumps, and flanges in high-temperature reactors.
- Marine: Exhaust systems and seawater-cooled components.
- Medical: Equipment and tools used in high-stress, high-temperature environments.