Inconel 625
2.4856Nickel-chromium-molybdenum-niobium superalloy. Solid-solution strengthened (no precipitation hardening required). Outstanding corrosion resistance from cryogenic to 982°C. Used for jet engine exhaust systems, marine components, chemical processing, flare stacks, and nuclear applications.
International equivalents
| Flag | Standard | Country | Grade | Number | Match |
|---|---|---|---|---|---|
| 🇺🇸 | ASTM | USA | UNS N06625 | N06625 | REF |
| 🇪🇺 | EN | Europe | NiCr22Mo9Nb | 2.4856 | 100% |
| 🇬🇧 | BS | United Kingdom | NA21 | — | 98% |
| 🇫🇷 | AFNOR | France | NC22DNb | — | 97% |
Sources: ASTM B443, DIN 17744, BS 3072, AFNOR
Chemical composition comparison (wt%)
Side-by-side: Inconel 625 (ASTM) (ASTM B443) vs NA21 (BS)
| Element | Inconel 625 (ASTM) | NA21 (BS) | Overlap |
|---|---|---|---|
| C | 0–0.1% | — | — |
| Si | 0–0.5% | — | — |
| Mn | 0–0.5% | — | — |
| Cr | 20–23% | — | — |
| Mo | 8–10% | — | — |
| Ni | ≥ 58% | — | — |
| Al | 0–0.4% | — | — |
| Ti | 0–0.4% | — | — |
| Nb | 3.15–4.15% | — | — |
| Co | 0–1% | — | — |
| Fe | 0–5% | — | — |
Mechanical properties
Annealed
| Property | Value | Unit |
|---|---|---|
| Tensile Strength | ≥ 827 | MPa |
| Yield Strength | ≥ 414 | MPa |
| Elongation | ≥ 30 | % |
| Elastic Modulus | ≥ 205 | GPa |
| Density | ≥ 8.44 | g/cm3 |
Heat treatment
| Process | Temperature | Medium | Holding Time | Notes |
|---|---|---|---|---|
| solution_treating_high | 1093–1204 °C | air | 1 hour min | Grade 2: For creep resistance above 593°C. High solution anneal. |
| solution_treating_low | 927–1038 °C | air | 1 hour min | Grade 1: For service up to 593°C. Best tensile + rupture balance. |
| stress_relief | 899–899 °C | air | 1 hour | For maximum fatigue and tensile strength below 649°C |
Compatibility verdict
Inconel 625 and NA21: 98% 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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