Inconel 625
A strong, corrosion-resistant Ni-Cr-Mo-Nb nickel alloy
Typical values for the temper in the title
Inconel 625 contains about 21% chromium, 9% molybdenum and about 3.6% niobium. Molybdenum and niobium strengthen it in solid solution, so it is very strong even without heat treatment (about 830–1030 MPa tensile). Its pitting and crevice resistance is excellent, including in seawater.
It is used in marine, chemical, oil and gas (listed in NACE MR0175), aircraft engines and exhaust systems. Its welding filler (ERNiCrMo-3) is also used as an "overalloyed" filler for super-austenitic stainless steels.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | 827–1034 MPa | |
| Yield strength Rp0.2 | 414–758 MPa | |
| Elongation A | 30% | |
| Hardness | 180–280 HB | |
| Modulus of elasticity E | 207 GPa | |
| Density ρ | 8.44 g/cm³ | |
| Machinability | 20% | relative rating in the site database |
Chemical composition (wt %)
| Element | Range | Role |
|---|---|---|
| Ni nickel | min 58.0 | |
| Cr chromium | 20.0–23.0 | oxidation and corrosion resistance |
| Mo molybdenum | 8.0–10.0 | pitting resistance, strengthening |
| Nb+Ta niobium | 3.15–4.15 | strengthening |
| Fe iron | max 5.0 | |
| Co cobalt | max 1.0 | |
| Al / Ti | max 0.40 each | |
| C carbon | max 0.10 |
Ranges per Special Metals and Daido data (UNS N06625).
Conditions and heat treatment
A solid-solution alloy: it is not hardened by heat treatment, and is supplied annealed or cold worked.
| Condition | Properties | When to choose it |
|---|---|---|
| Annealed (Grade 1) | high strength | most uses up to about 600 °C |
| Solution annealed (Grade 2) | better creep resistance | high-temperature service |
Applications
- Marine equipment and subsea components
- Chemical equipment
- Oil and gas (NACE MR0175)
- Exhaust systems and aircraft engines
- Weld overlay and filler wire
Fabrication
Welding
Welds well by TIG and MIG. Careful cleaning before welding is especially important: oil, paint or sulfur on the surface cause weld cracking. With ERNiCrMo-3 filler.
Machining
Nickel alloys work harden, stay strong when hot, and wear tools. Use low speed, a steady feed that does not "rub", sharp rigid tools and plenty of coolant.
Corrosion
Excellent pitting and crevice resistance, including in warm seawater.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| Hastelloy C-276 | 690–1000 / 350–460 MPa | Good — ERNiCrMo-4 | more resistant in reducing environments · material page |
| Inconel 718 | 1240–1380 / 1035–1170 MPa | Good — ERNiCrMo-6 | age hardened, stronger · material page |
| 254 SMO | 650 / 295 MPa | Good — ERNiCrMo-3 | a 6Mo stainless, cheaper · material page |
Common mistakes
Using stainless machining parameters
625 is stronger and work hardens fast. Low speed and rigid tools.
Welding with non-matching filler
The weld becomes the weak link in corrosion.
Choosing 625 where 316L is enough
The price difference is very large.
Equivalents, standards and supply
| EN | 2.4856 |
|---|---|
| DIN | NiCr22Mo9Nb |
| JIS | NCF625 |
| Standards | ASTM B443 / AMS 5599 / ISO 6208 |
| Forms | plate · rod · pipe · welding wire |
| Producers | Special Metals · Haynes Int. · VDM · Valbruna |
Learn more
Values are typical and for comparison only. For design, rely on the standard and the mill certificate. Sources: ASTM (B127, B164, B168, B443, B575, B619 and others), Special Metals and Haynes data sheets, and the METAL HUB materials database. Inconel and Monel are trademarks of Special Metals, and Hastelloy of Haynes International.
Updated: October 31, 2026