Inconel 690
2.4642High-chromium (27-31%) nickel alloy — THE nuclear PWR steam generator tube material, replacing Inconel 600 due to superior SCC resistance. Ni 58% min + Cr 30% = exceptional resistance to oxidizing media, nitric acid, and high-temperature atmospheres. Also used for coal gasification, radioactive waste processing, and sulfuric/hydrofluoric acid environments.
International equivalents
| Flag | Standard | Country | Grade | Number | Match |
|---|---|---|---|---|---|
| 🇺🇸 | UNS | USA | UNS N06690 | N06690 | REF |
| 🇪🇺 | EN | Europe | NiCr29Fe / 2.4642 | 2.4642 | 100% |
Sources: ASTM B168, EN 10095
Chemical composition comparison (wt%)
Side-by-side: Inconel 690 (UNS) (ASTM B168) vs NiCr29Fe / 2.4642 (EN)
| Element | Inconel 690 (UNS) | NiCr29Fe / 2.4642 (EN) | Overlap |
|---|---|---|---|
| C | 0–0.05% | — | — |
| Si | 0–0.5% | — | — |
| Mn | 0–0.5% | — | — |
| Cr | 27–31% | — | — |
| Ni | ≥ 58% | — | — |
| Fe | 7–11% | — | — |
Mechanical properties
Annealed
| Property | Value | Unit |
|---|---|---|
| Tensile Strength | ≥ 586 | MPa |
| Yield Strength | ≥ 241 | MPa |
| Elongation | ≥ 30 | % |
| Elastic Modulus | ≥ 211 | GPa |
| Density | ≥ 8.19 | g/cm3 |
Compatibility verdict
Inconel 690 and NiCr29Fe / 2.4642: 100% composition match
Close equivalents but NOT identical.
Related materials
Hastelloy C-22
2.4602Improved version of Hastelloy C-276 with better resistance to oxidizing media and higher chromium. Considered the most versatile Ni-Cr-Mo alloy for chemical processing. Resists both oxidizing and reducing acids, chlorides, and mixed media. Used for flue gas desulfurization, pharmaceutical, and universal chemical processing.
Alloy 20 / Carpenter 20
2.4660Austenitic Ni-Fe-Cr alloy specifically developed for sulfuric acid resistance. Nb-stabilized against sensitization. Cu addition gives outstanding resistance to H2SO4 at all concentrations up to 80%. Used for sulfuric acid piping, heat exchangers, mixing tanks, pickling equipment, and pharmaceutical processing.
Nimonic 80A
2.4952Nickel-chromium age-hardenable alloy with Ti + Al for gamma-prime strengthening. Developed originally for gas turbine blades. Good creep resistance to ~700°C. Used for exhaust valves, springs at elevated temperatures, nuclear engineering fasteners, and gas turbine components. ≈ UNS N07080.
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