Inconel 718 at a glance
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Designation
| Item | Value |
|---|---|
| Designation | Inconel 718 |
| Class | Nickel alloys |
| Type | nickel-base alloy |
Composition
| Item | Limit | Source |
|---|---|---|
| Composition | Nickel 50–55 %, chromium 17–21 %, niobium 4.75–5.5 %, molybdenum 2.8–3.3 %, titanium 0.65–1.15 %, aluminum 0.2–0.8 %, iron balance | Special Metals, Inconel alloy 718 bulletin, limiting chemical composition |
Properties
| Property | Value | Source |
|---|---|---|
| Type | Vacuum-melted, precipitation-hardened nickel-base alloy | MIL-HDBK-5J, par. 6.3.5.0 |
| Use range | Creep and stress rupture to 1,300 °F, strength at cryogenic temperature, oxidation resistance to 1,800 °F | MIL-HDBK-5J, par. 6.3.5.0 |
| Welding and forming | Welded easily, excels in resistance to strain-age cracking, readily formable | MIL-HDBK-5J, par. 6.3.5.0 |
| Sheet | AMS 5596 (sheet), 5597 (plate), 5589 (sheet and plate) | MIL-HDBK-5J, Table 6.3.5.0(b) |
| Tubing | AMS 5590 | MIL-HDBK-5J, Table 6.3.5.0(b) |
Design allowables — Inconel 718 sheet, solution treated and aged (AMS 5596)
Sheet 0.010–0.187 in. MIL-HDBK-5J Table 6.3.5.0(b), p. 6-52.
| Property | A basis | B basis | Unit |
|---|---|---|---|
| Ftu, L | 180 | 192 | ksi |
| Ftu, LT | 180 | 191 | ksi |
| Fty, L | 145 | 156 | ksi |
| Fty, LT | 147 | 158 | ksi |
| Fcy, LT | 158 | 170 | ksi |
| Fsu | 124 | 132 | ksi |
| Elongation LT (S basis) | 12 | — | % |
| E | 29.4 | 29.4 | 10³ ksi |
| Density | 0.297 | 0.297 | lb/in³ |
Design allowables come from material supplied solution treated and aged by the suppliers to show heat-treatment response; properties of material formed or cold worked may be different. Plate and AMS 5589 columns carry S-basis values around 180 ksi; G = 11.4 × 10³ ksi.
Notes from the guide
- Heat-treated design values. They do not apply after welding or hot work without the correct treatment.
- The engine or airframe manual governs repairs.
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Sources
- MIL-HDBK-5J, Metallic Materials and Elements for Aerospace Vehicle Structures (31 Jan 2003) — par. 6.3.5.0 and Table 6.3.5.0(b), p. 6-52. Cancelled; superseded by MMPDS.
- FAA-H-8083-31B, Aviation Maintenance Technician Handbook, Airframe, Volume 1 — Working Inconel Alloys 625 and 718, p. 4-82, Figure 4-166.
- MMPDS (formerly MIL-HDBK-5) — the current home of design allowables. A repair substantiation cites MMPDS or the SRM, not a website.
- Special Metals, Inconel alloy 718 — Limiting chemical composition.
Educational reference only. not approved data. Always consult the applicable SRM, AMM, or AC 43.13-1B and your certifying authority.