Alloy 718
- ALLOY 718 • UNS N07718 • WNR 2.4668
Alloy 718 was initially developed for the aerospace industry but its excellent strength and corrosion resistance were recognised by the oil industry and it is now widely used in this field also.
Alloy 718 is a nickel-chromium alloy with additions of niobium & molybdenum which can be heat-treated to give high strength, good corrosion resistance, ease of formability and which can be welded with good resistance to strain age cracking. The alloy can be used at temperatures up to 700ºC.
Alloy 718 for the oil industry is heat treated such that the hardness does not exceed 40HRC which is the maximum allowed by NACE MR-01-75/ ISO 15156: 3 to prevent stress corrosion cracking. The major applications in this field are Valves and precision tubing.
Alloy 718 for aerospace and power generation is heat treated to give maximum strength and high creep resistance with typical hardness values exceeding 42HRC. The major applications are components for gas turbines, aircraft engines, fasteners and other high strength applications.
- Available Tube Product form
- Straight
- Seamless
- Typical Applications
- Heat exchangers
- Well Head Completion Equipment
- Mandrels
- Valves
- Industries predominantly using this Grade
- Aerospace
- Oil and gas
- Nuclear and Power
- Typical Manufacturing Specifications
- AMS 5589
- AMS 5590
- Also Individual Customer Specifications.
- Technical Data
Mechanical Properties
| Temper | Solution-treated | |
| Tensile Rm | 155 | ksi (min) |
| Tensile Rm | 1069 | MPa (min) |
| R.p. 0.2% Yield | 95 | ksi (min) |
| R.p. 0.2% Yield | 655 | MPa (min) |
| Elongation (2” or 4D gl) | 30 | % (min) |
Physical Properties (Room Temperature)
| Specific Heat (0-100°C) | 435 | J.kg-1.°K-1 |
| Thermal Conductivity | 11.4 | W.m -1.°K-1 |
| Thermal Expansion | 13 | μm/μm/°C |
| Modulus Elasticity | 200 | GPa |
| Electrical Resistivity | 1.32 | Ohm-cm |
| Density | 8.19 | g/cm3 |
Chemical Composition (% by weight)
| Element | Min | Max |
| C | - | 0.08 |
| Si | - | 0.35 |
| Mn | - | 0.35 |
| P | - | 0.015 |
| Ai | 0.2 | 0.8 |
| B | - | 0.6 |
| Co | - | 1 |
| Cr | 17 | 21 |
| Cu | - | 0.3 |
| Fe | Balance | |
| Mo | 2.8 | 3.3 |
| Nb | 4.75 | 5.5 |
| Ni | 50 | 55 |
| Ti | 0.65 | 1.15 |
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