Alloy 625
Also known as Inconel® 625, UNS N06625, Werkstoff 2.4856
Alloy 625 is a nickel-chromium-molybdenum alloy with excellent corrosion resistance from sub-zero to 980°C and high strength.
Alloy 625 (UNS N06625) is a Nickel-Chromium-Molybdenum-Niobium alloy providing excellent corrosion and fatigue resistance in severe environments from sub-zero temperatures to over 980°C. Strength is derived from the solid-solution effects of molybdenum and niobium on a nickel-chromium base - no precipitation hardening required.
Non-magnetic, spark-resistant and with a Curie temperature of -196°C, it is listed in NACE MR0175 / ISO 15156 for sour service and is resistant to high temperature oxidation and carburisation. Supplied hot worked and annealed.
We stock bar in the UK and USA. Plate, tube and fittings are available on enquiry; forgings and castings to order.
- Good strength and ductility from sub-zero to over 980°C
- Excellent corrosion and fatigue resistance in seawater and industrial acids
- Non-magnetic and spark resistant
- Resistant to high temperature oxidation and carburisation
- Excellent resistance to stress corrosion cracking
| Element | Min | Max |
|---|---|---|
| Nickel (Ni) | 58.0 | - |
| Chromium (Cr) | 20.0 | 23.0 |
| Molybdenum (Mo) | 8.0 | 10.0 |
| Niobium+Tantalum (Nb+Ta) | 3.15 | 4.15 |
| Iron (Fe) | - | 5.0 |
| Cobalt (Co) | - | 1.0 |
| Titanium (Ti) | - | 0.40 |
| Aluminium (Al) | - | 0.40 |
| Manganese (Mn) | - | 0.50 |
| Silicon (Si) | - | 0.50 |
| Carbon (C) | - | 0.10 |
| Phosphorus (P) | - | 0.015 |
| Sulphur (S) | - | 0.015 |
| Property | Imperial | Metric |
|---|---|---|
| 0.2% Proof stress (min) | 60 ksi | 415 N/mm² |
| Tensile strength (min) | 120 ksi | 830 N/mm² |
| Elongation (5.65√S0 & 4D) | 30% | |
| Reduction of area | 35% |
| Property | Imperial | Metric |
|---|---|---|
| 0.2% Proof stress (min) | 50 ksi | 345 N/mm² |
| Tensile strength (min) | 110 ksi | 760 N/mm² |
| Elongation (5.65√S0 & 4D) | 25% | |
| Reduction of area | 35% |
| Property | Value |
|---|---|
| Density (kg/m³) | 8440 |
| Magnetic permeability (20°C) | < 1.001 |
| Curie temperature (°C) | -196 |
| Young's modulus (kN/mm²) | 207.5 |
| Specific heat, 20°C (J/kg.K) | 410 |
| Specific electrical resistance, 20°C (Ω.m) | 0.0129 |
| Thermal conductivity, 20°C (W/m.K) | 9.9 |
| Mean coefficient of thermal expansion, 20-100°C (m/m/K) | 12.8 x 10⁻⁶ |
Equivalents & cross-references
Standard designations
- UNS
- N06625Unified Numbering System
- Werkstoff
- 2.4856German/European material number; NiCr22Mo9Nb
- ASTM
- B446Rod and bar
- AMS
- 5666Bar, rod, wire and forgings
- BS
- 3076British Standard nickel alloys
- NACE
- MR0175 / ISO 15156Sour service
Alloy 625 is also designated UNS N06625, Werkstoff 2.4856, ASTM B446, AMS 5666, BS 3076 and NACE MR0175 / ISO 15156.
Trade name equivalents
-
Inconel 625
Special Metals Corporation
Inconel 625 is a trade name of Special Metals Corporation for Alloy 625.
Common questions
What is the UNS number for Alloy 625?
Alloy 625 is a nickel-chromium-molybdenum-niobium alloy (NiCr22Mo9Nb) covered by UNS N06625, Werkstoff No. 2.4856, ASTM B446, AMS 5666 and BS3076, and is listed in NACE MR0175/ISO 15156. It is supplied in the hot worked and annealed condition and gains high strength from the solid solution effects of molybdenum and niobium from room temperature up to 800°C. Langley Alloys stocks it as bar; plate, tube and fittings are available on enquiry, and forgings and castings are to order.
What is Alloy 625 used for?
Alloy 625 is used for wellhead components, downhole equipment for corrosive and sour service, sheathing, fasteners and clamps; propellers, shafts and propulsion motors; reactor core and control rod components; and chemical process equipment. It provides excellent corrosion and fatigue resistance in a wide variety of severe environments including seawater and industrial acids.
Is Alloy 625 suitable for high temperatures?
Yes. Alloy 625 retains good strength and ductility from sub-zero temperatures to over 980°C, and is resistant to high temperature oxidation and carburisation. It is non-magnetic and spark resistant, with excellent resistance to stress corrosion cracking. In the annealed condition it is fully austenitic and suitable for machining.
What is AMS 5666?
AMS 5666 is the SAE aerospace material specification for UNS N06625 (Alloy 625) bar, rod, wire, and forgings. Langley Alloys supplies Alloy 625 to this specification alongside ASTM B446 and NACE MR0175/ISO 15156.
What is Werkstoff 2.4856?
Werkstoff No. 2.4856 (NiCr22Mo9Nb) is the German/European material number for UNS N06625, a nickel-chromium-molybdenum-niobium alloy stocked by Langley Alloys as Alloy 625.
What is the density of Alloy 625?
Alloy 625 has a density of approximately 8.44 g/cm³ (8440 kg/m³).
Is Alloy 625 magnetic?
No. Alloy 625 is non-magnetic, with a magnetic permeability below 1.001.
Datasheets
Corrosion resistance across the widest range
In this Technical Corner, Rodney covers Alloy 625: a long-established nickel alloy with perhaps the most corrosion-resistant, versatile properties in our portfolio.
With a PREN of 45 (against 31 for 718) and a high nickel content that resists oxidation from cryogenic temperatures up to 900°C, it suits an exceptionally wide range of aerospace and chemical-processing applications.
Visit our YouTube channelAlloy 625 is supplied in the hot worked and annealed condition, annealed above 875°C with water or air quench, with each complete batch ultrasonically tested and all bars visually inspected.
Tools for this grade
Sour-service screen (NACE MR0175)
Sour-Service Screen
Work out whether a service is sour from the H2S partial pressure, and see each alloy's NACE MR0175 / ISO 15156 status and hardness limit. A first-pass screen for oil & gas material selection - the full environmental envelope for a grade is set in ISO 15156-3 Annex A.
Candidate grade
| Grade | Family | NACE status | Hardness limit |
|---|
First-pass screen only. This shows whether the service is sour (from H2S partial pressure) and each material group's NACE MR0175 hardness limit and general suitability. It does not reproduce the full environmental windows (maximum H2S partial pressure, temperature, chloride, in-situ pH per grade) - those are in ISO 15156-3 Annex A and must be checked there for the specific grade, product form and condition. Qualification also depends on heat treatment, cold work and welding.
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