Specifications
| 2.4668 | ASTM B637 | UNS N07718 |
| API 6CRA 718 | NACE MR 01-75 / ISO 15156-3 | – |
Alloy 718
Alloy 718 is a high-strength, corrosion-resistant nickel chromium alloy supplied in the hot worked, solution annealed and age hardened condition. It possesses acceptable corrosion resistance in a range of environments and is resistant to sulphide stress cracking. It also features exceptional welding properties, making it suitable for a wide range of applications. It also offers high levels of corrosion resistance and strength, making it ideal for applications in oil and gas and chemical process industries.
Chemical Composition Limits
| Cr | Ni | Mo | Co | Nb (+Ta) | Ti | V | W | Cu | C | Mn | N | Si | P | S | Fe | Al | |
| Min | 17.00 | 50.00 | 2.80 | – | 4.70 | 0.65 | – | – | – | – | – | – | – | – | – | – | 0.20 |
| Max | 21.00 | 55.00 | 3.30 | 1.00 | 5.50 | 1.15 | – | – | 0.30 | 0.08 | 0.35 | – | 0.35 | 0.015 | 0.015 | Bal | 0.80 |
Mechanical Properties
| Age hardened 120 ksi | Age hardened 140 ksi | |||||||
| Bars up to and including 10” (254) diameter or section | Bars greater than 10” (254mm) diameter or section | Bars up to and including 10” (254) diameter or section | Bars greater than 10” (254mm) diameter or section | |||||
| 0.2% Proof Stress, min | 827 N/mm2 | 125 ksi | 827 N/mm2 | 125 ksi | 965 N/mm2 | 140 ksi | 965 N/mm2 | 140 ksi |
| 0.2% Proof Stress, max | 1000 N/mm2 | 145 ksi | 1000 N/mm2 | 145 ksi | 1034 N/mm2 | 150 ksi | 1034 N/mm2 | 150 ksi |
| Tensile strength, min | 1034 N/mm2 | 150 ksi | 1034 N/mm2 | 150 ksi | 1138 N/mm2 | 165 ksi | 1103 N/mm2 | 160 ksi |
| Elongation, 5.65√S0 and 4D | 20% | – | 20% | – | 20% | – | 20% | – |
| Reduction of Area | 35% | – | 25% | – | 35% | – | 25% | – |
| Hardness (Rockwell C) | 32-40HRC | – | 32-40HRC | – | 34-40 HRC | – | 34-40HRC | – |
| Impact Strength (-60oC) Longitudinal | <3” | <3” | – | – | <3” | <3” | – | – |
| 68J av (61J min) | 50 ft.lb av (45 ft.lb min) | 68J av (61J min) | 50 ft.lb av (45 ft.lb min) | |||||
| Impact Strength (-60oC) Transverse | ≥3” – 10” | ≥3” – 10” | 41J av (37J min) | 30 ft.lb av (27 ft.lb min) | ≥3” – 10” | ≥3” – 10” | 41J av (37J min) | 30 ft.lb av (27 ft.lb min) |
| 47J av (41J min) | 35 ft.lb av (30 ft.lb min) | 47J av (41J min) | 35 ft.lb av (30 ft.lb min | |||||
Physical Properties
| Density (Kg/m3) | 8230 |
| Magnetic Permeability (20°C) | <1.002 |
| Young’s Modulus (kN/mm2) | 200 |
| Specific Electrical Resistance, 20°C (µΩ-m) | 1.25 |
| Mean coefficient of thermal expansion, 20-100°C (m/m/degC) | 12.1 x 10-6 |
| Specific Heat, 20°C (J/kg.K) | 435 |
| Thermal Conductivity, 20°C (W/m.K) | 11.1 |
| Curie Temperature (degC) | -112 (aged) |
Key Features
- Good strength/ductility properties from sub-zero temperatures to over 750°C.
- Acceptable corrosion resistance and fatigue resistance in a wide variety of corrosive chemicals such as seawater and industrial acids.
- Non-magnetic and spark resistant.
- Excellent resistance to stress corrosion cracking, chloride stress corrosion & sulphide stress cracking.
- High fatigue strength in seawater
Applications
- Oil & Gas industry wellhead components, gate valves, choke stems, fasteners, packers, clamps, tubing hangers, downhole equipment.
- Power generation applications such as fasteners, turbines.
- Aerospace components.
- Nuclear power plant containment vessels, valves.
- Engineering applications between 750°C and cryogenic temperatures.