Incoloy A286 and Inconel 718 are the two precipitation hardening alloys most often encountered in aerospace fasteners. Both harden with titanium and both retain their strength at high temperature. The difference is in which metal the matrix is based on.
Iron based, or nickel based?
According to our datasheets, A286 has iron at 49–59.5%, nickel at only 24–27% and chromium at 13.5–16.0%. In other words A286 is in fact an iron-based superalloy — an intermediate class between stainless steel and nickel alloy. Its UNS number reflects that: S66286, that is, the stainless group.
Inconel 718 has nickel at 50.0–55.0% and iron at 12.0–24.0%; with the UNS number N07718 it belongs to the nickel alloy group.
Their hardening mechanisms differ as well. A286 takes its strength from the gamma prime precipitates formed by 1.90–2.35% titanium; there is no niobium. 718 relies mainly on the precipitates of 4.75–5.50% niobium + tantalum.
The practical result shows in the temperature limit. A286 is used up to roughly 700 °C; 718, while close to the same limit, gives higher strength. The real advantage of A286 is cost — with half the nickel content it is markedly more economical.
Comparison in numbers
| PROPERTY | Incoloy A286 | Inconel 718 |
|---|---|---|
| Base metal | Iron | Nickel |
| Nickel (Ni) | 24 – 27% | 50.0 – 55.0% |
| Iron (Fe) | 49 – 59.5% | 12.0 – 24.0% |
| Chromium (Cr) | 13.5 – 16.0% | 17.0 – 21.0% |
| Molybdenum (Mo) | 1.0 – 1.5% | 2.80 – 3.30% |
| Titanium (Ti) | 1.90 – 2.35% | 0.65 – 1.15% |
| Aluminium (Al) | max 0.35% | 0.20 – 0.80% |
| Niobium + Tantalum | — | 4.75 – 5.50% |
| Vanadium (V) | 0.10 – 0.50% | — |
| Boron (B) | 0.001 – 0.010% | max 0.006% |
| Carbon (C) | max 0.08% | max 0.08% |
| Manganese (Mn) | max 2.00% | max 0.35% |
| Silicon (Si) | max 1.00% | max 0.35% |
| UNS | S66286 | N07718 |
| W.Nr (DIN/EN) | 1.4980 | 2.4668 |
| AMS | 5731 · 5732 · 5737 | 5596 · 5663 |
Values are taken from our product datasheets; section thickness and the applied heat treatment regime change the result.
Which one, and when?
Incoloy A286 is preferred — aerospace and automotive fasteners, turbocharger parts, exhaust valves, spring and ring applications, moderately stressed parts below 700 °C. Its cost advantage is clear and it machines more easily than 718.
Inconel 718 is required — turbine discs and blades, highly stressed structural fasteners, rocket engine parts, cryogenic applications. If the specification calls out AMS 5596 or AMS 5663, A286 is not an acceptable substitute.
Neighbouring alloys
For higher temperatures, see our Inconel 718 – Waspaloy comparison; for the solid solution alternative, our Inconel 625 – 718 article.
Technical datasheets
Incoloy A286 — chemical composition, mechanical values, standard equivalents
Inconel 718 — chemical composition, mechanical values, standard equivalents
Both grades are supplied to order in round bar, flat bar, plate, sheet, pipe and forged forms. Contact us for a quotation.