Introduction Inconel 718 is a Nickel-Chromium alloy being precipitation hardenable and having high creep-rupture strength at high temperatures to about 700°C (1290°F). It has higher strength thanInconel X-750 and better mechanical properties at lower temperatures than Nimonic 90 andInconel X-750. Chemical Composition of Inconel 718 The compositional range for Inconel 718 is provided in the table below. Element | Ni+Co | 50 – 55 % | Cr | 17 – 21 % | Fe | BAL | Nb+Ta | 4.75 – 5.5 % | Mo | 2.8 – 3.3 % | Ti | 0.65 – 1.15 % | Al | 0.2 – 0.8 % | Typical Properties of Inconel 718 Typical properties of Inconel 718 are covered in the following table. Property | Density | 8.19 g/cm3 | 0.296 lb/in3 | Melting point | 1336 °C | 2437 °F | Co-Efficient of Expansion | 13.0 µm/m.°C (20-100 °C) | 7.2×10-6 in/in.°F (70-212 °F) | Modulus of rigidity | 77.2 kN/mm2 | 11197 ksi | Modulus of elasticity | 204.9 kN/mm2 | 29719 ksi | Properties of Supplied Materials and Heat Treated Materials Condition of Supply | No.1 Spring Temper/Spring Temper | 1. Solution Anneal at 980°C (1800°F) for 1 hour and air cool and 2. Age harden at 720°C (1330°F) for 8 hours and furnace cool to 620°C (1150°F) and hold at 620°C (1150°F) for a total age hardening time of 18 hours and air cool. | No.1 Spring Temper/Spring Temper (NACE MRO175) | 1. 1010°C (1870°F) 2 hours and air cool and 2. 790°C (1455°F) 6 hours and air cool. | Condition | Annealed | 800 – 1000 N/mm2 | 116 – 145 ksi | – | - | No.1 Spring Temper | 1000 – 1200 N/mm2 | 145 – 175 ksi | – | - | No.1 Spring Temper + Annealed + Aged | 1250 – 1450 N/mm2 | 181 – 210 ksi | -200 to +550°C | -330 to +1020°F | Spring Temper | 1300 – 1500 N/mm2 | 189 – 218 ksi | – | - | Spring Temper + Annealed + Aged | 1250 – 1450 N/mm2 | 181 – 210 ksi | -200 to +550°C | -330 to +1020°F | Relevant Standards Inconel 718 is covered by the following standards: • AMS 5663 • AMS 5832 • AMS 5962 • AMS 5662 • ASTM B637 Equivalent Materials Inconel 718 is the tradename of Special Metals Group of Companies and equivalent to: • W.NR 2.4668 • UNS N07718 • AWS 013 Applications of Inconel 718 Inconel 718 typically finds application in: • Gas turbines • Rocket motors • Space craft • Nuclear reactors and pumps. |