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Alloy 625
ISO S (heat-resistant alloys & titanium)Solid solution strengthened nickel-base alloy (Ni-Cr-Mo-Nb). Number: UNS N06625. Standard: ASTM B446 (bar) / ASTM B443 (plate) / ASTM B564 (forgings) / SAE AMS 5666 (bar, forgings, rings) / AMS 5599 (plate).
🌐JIS and international equivalents
“Close” means composition or properties are not exactly the same. Before substituting, check the values in each standard.
| System | Designation | Number | Relation | Confidence |
|---|---|---|---|---|
| UNS | Alloy 625 | UNS N06625 | — | |
| EN | NiCr22Mo9Nb | 2.4856 | close | Agrees in 2+ sources[9][1][7] |
| ISO | NW6625 | NW6625 | equivalent | One source / reference[1] |
| JIS | NCF625 | JIS G 4904 (tubes for heat exchangers) | equivalent | One source / reference[7] |
| GB | — | — | Not confirmed |
Differences between the equivalents (from the sources)
- EN NiCr22Mo9Nb: Number 2.4856 agrees across Special Metals, VDM and Nippon Steel. The symbol NiCr22Mo9Nb is from VDM only. VDM writes C as 0.03–0.10 and Cu≤0.50 for EN 10095, which differ from the UNS ranges (C≤0.10)
- ISO NW6625: Special Metals lists it together with ISO NW6625
- JIS NCF625: Nippon Steel's tube catalog lists NCF625 (JIS G 4904) = N06625 (ASTM B444) = 2.4856 on the same row. The composition in the table is C≤0.10, Si≤0.50, Mn≤0.50, P≤0.015, S≤0.015, Ni≥58.00, Cr 20.00–23.00, Mo 8.00–10.00, Fe≤5.00, Al≤0.40, Ti≤0.40, Nb+Ta 3.15–4.15, which agrees with UNS. No material directly listing NCF625 for bar (JIS G 4901) or plate (G 4902) was found
- GB : Material giving GH3625 is only from distributors' pages, and no primary source was found
📄Related specifications (AMS, ASTM etc.)
Specifications called up on purchase orders and drawings. AMS are SAE aerospace material specifications, split by product form (bar, plate, forging), melting practice and heat treatment. Standard texts are paid, so only titles and scopes checked on the publishers’ public pages are shown.
| Spec | Scope | Confidence |
|---|---|---|
| ASTM B446 | Standard Specification for Nickel-Chromium-Molybdenum-Niobium Alloy, Nickel-Chromium-Molybdenum-Silicon Alloy, and Nickel-Chromium-Molybdenum-Tungsten Alloy Rod and BarBar (hot and cold worked) of N06625 and others. N06625 is delivered in grades with different heat treatments, such as Grade 1 (annealed. Normally used up to 593℃) | Agrees in 2+ sources[10][1] |
| ASTM B443 | Standard Specification for Nickel-Chromium-Molybdenum-Columbium Alloy and Nickel-Chromium-Molybdenum-Silicon Alloy Plate, Sheet, and StripRolled plate, sheet and strip of N06625 and others. Two grades: Grade 1 (annealed) and Grade 2 (solution treated) | Agrees in 2+ sources[11][1] |
| AMS 5666 | Bar, forgings and rings (listed by Special Metals, ATI, Haynes and Carpenter as the applicable specification for 625) | One source / reference[1][8][12] |
| AMS 5599 | Plate, sheet and strip (listed by Special Metals, ATI and Haynes) | One source / reference[1][8][13] |
All ASTM standards on Kezuriba: ASTM standards quick reference.
✈Main aerospace uses (as stated in the sources)
- Aircraft ducting systems, engine exhaust systems, thrust reversers, resistance-welded honeycomb structures housing engine control equipment, fuel and hydraulic piping, spray bars, bellows, turbine shroud rings, heat exchanger tubes for environmental control systems, combustor transition liners, turbine seals, compressor vanes, rocket thrust chamber tubing[1]
- Widely used in airframe and jet engine applications[8]
- Widely used in high-temperature aerospace applications. However, prolonged use above about 593℃ (1100°F) causes embrittlement, so long-term high-temperature use is preferably limited to 593℃[2]
⚗Chemical composition (mass %)
As specified in UNS N06625 (Special Metals' Limiting Chemical Composition)
| Element | Range | Confidence |
|---|---|---|
| Ni | ≥ 58 | One source / reference[1] |
| Cr | 20 – 23 | Agrees in 2+ sources[1][6] |
| Fe | ≤ 5 | Agrees in 2+ sources[1][6] |
| Mo | 8 – 10 | Agrees in 2+ sources[1][6] |
| Nb | 3.15 – 4.15 | Agrees in 2+ sources[1][6] |
| C | ≤ 0.1 | Agrees in 2+ sources[1][6] |
| Mn | ≤ 0.5 | Agrees in 2+ sources[1][6] |
| Si | ≤ 0.5 | Agrees in 2+ sources[1][6] |
| P | ≤ 0.015 | Agrees in 2+ sources[1][6] |
| S | ≤ 0.015 | Agrees in 2+ sources[1][6] |
| Al | ≤ 0.4 | Agrees in 2+ sources[1][6] |
| Ti | ≤ 0.4 | Agrees in 2+ sources[1][2] |
| Co | ≤ 1 | Agrees in 2+ sources[1][2] |
⚖Density
8.44 g/cm³
Special Metals (0.305 lb/cu in, 8.44 gram/cc), Haynes (8.44 g/cm³) and ATI (8.44 g/cm³) agree. VDM gives 8.47 g/cm³
Calculate weight in Alloy 625 →💪Mechanical properties
“Reference” values are not specified minimums from the standard but figures published by makers and others.
| Condition | Tensile MPa | Yield MPa | Elong. % | Hardness | Type of value |
|---|---|---|---|---|---|
| Bar and plate: annealed | 827–1034 | 414–655 | 30–60 | HB 145–220 | Range of typical values (Special Metals. Composite values for each size up to 4in diameter; states they are not for specifications) One source / reference[1] |
| Bar and plate: solution treated | 724–896 | 290–414 | 40–65 | HB 116–194 | Range of typical values (Special Metals. States they are not for specifications) One source / reference[1] |
| Heat exchanger tube NCF625 (JIS G 4904) | ≥ 690 | ≥ 275 | ≥ 30 | — | JIS specified value (tube. Listed in Nippon Steel catalog) One source / reference[7] |
| Annealed / aged | — | — | — | Annealed HRB 88 to HRC 25 (depending on annealing temperature), up to about HRC 40 by aging low-carbon material, HRC 36–42 with 30–60% cold work | Typical value (ATI datasheet) One source / reference[8] |
1 MPa ≈ 145 psi (0.145 ksi). Hardness conversion · unit converter
🔧Machinability notes (as stated in the sources)
- VDM: machine in the annealed condition. Because it work hardens readily, use a low cutting speed and an appropriate feed, and keep the tool continuously engaged. A depth of cut reaching below the work-hardened layer is important. Removing heat with plenty of water-soluble cutting fluid is the key to stable machining[9]
- ATI: it is best machined in the annealed condition, in the same way as other high-strength nickel-base alloys[8]
- Sandvik Coromant cites Inconel 625 as an example of an ISO S solid solution strengthened (non-hardening) nickel-base alloy. ISO S materials have high strength at high temperature, large fluctuations in cutting force from serrated chips, work hardening and built-up edge hardening, and notch wear at the depth-of-cut line[4]
- Special Metals' datasheet gives a table of recommended conditions for turning with single-point tools (Table 12) and refers to its separate booklet "Machining" for details[1]
📚Sources
Primary sources (public documents from makers, industry associations and standards bodies), numbered where each value is cited. Many are in Japanese.
- specialmetals.com https://www.specialmetals.com/documents/technical-bulletins/inconel/inconel-alloy-625.pdf
- haynesintl.com https://haynesintl.com/wp-content/uploads/2023/06/625-brochure.pdf
- atimaterials.com https://atimaterials.com/Products/Documents/datasheets/nickel-cobalt/nickel-based/ati_625_…
- sandvik.coromant.com https://www.sandvik.coromant.com/en-us/knowledge/materials/workpiece-materials
- kyocera.co.jp https://www.kyocera.co.jp/prdct/tool/wp-content/uploads/2014/07/2024-2026_A.pdf
- carpentertechnology.com https://www.carpentertechnology.com/alloy-finder/625
- www-zam.nipponsteel.com https://www-zam.nipponsteel.com/product/pipe/list/pdf/P007_8-9.pdf
- atimaterials.com https://www.atimaterials.com/Products/Documents/datasheets/nickel-cobalt/nickel-based/ati_…
- vdm-metals.com https://www.vdm-metals.com/fileadmin/user_upload/Downloads/Data_Sheets/Data_Sheet_VDM_Allo…
- store.astm.org https://store.astm.org/standards/b446
- store.astm.org https://store.astm.org/standards/b443
- saemobilus.sae.org https://saemobilus.sae.org/standards/ams5666-alloy-bars-forgings-rings-corrosion-heat-resi…
- saemobilus.sae.org https://saemobilus.sae.org/standards/ams5599-alloy-sheet-strip-plate-corrosion-heat-resist…
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