NiCr21Mo at a glance
Reference data for NiCr21Mo forgings.
- EN / DIN name
- NiCr21Mo (DIN 17744)
- Werkstoff number
- 2.4858
- UNS number
- N08825
- Common name
- Alloy 825 · Incoloy® 825
- Other designations
- BS NA16 · AFNOR NC21FeDU · ISO NiFe30Cr21Mo3 · JIS NCF825
- Alloy type
- Solid-solution Ni-Fe-Cr alloy with Mo and Cu, stabilised with Ti. Not age-hardenable.
- Forging standard
- ASTM B564 / ASME SB-564
- Sour service
- NACE MR0175 / ISO 15156 · API 6CRA · NACE MR0103
- Density
- 8.14 g/cm³
- Melting range
- 1370–1400 °C
- Usual service limit
- about 540 °C in corrosive service
- Delivery condition
- Hot forged, stabilise annealed ≈940 °C, rapid cool
Another name on your drawing?
This page uses the EN/DIN designation. If your purchase order carries a different name, see 2.4858 forgings for the Werkstoff number or Incoloy 825 forgings for the trade name. The material, the forging route and the certificate are the same. Only the wording on the paperwork changes.
Incoloy® is a registered trademark of Special Metals Corporation. Jiangyin Jiangnan Metal Co., Ltd. is not affiliated with that company. The name is used here only to identify the equivalent grade.
What is NiCr21Mo, and why does it have so many names?
NiCr21Mo is one alloy with several national names. The German material number 2.4858 and the short name NiCr21Mo come from DIN 17744. The American designation is UNS N08825, written as Alloy 825 on most purchase orders. Britain calls it NA16, France NC21FeDU, Japan NCF825 and ISO NiFe30Cr21Mo3. Incoloy 825 is the trade name Special Metals Corporation registered for the same chemistry. A forging ordered under any of these names is the same material, so a drawing calling for 2.4858 can be quoted against ASTM B564 UNS N08825 without a deviation.
Each addition has a job. The high nickel content resists chloride-ion stress corrosion cracking, the usual failure mode of austenitic stainless steel in hot chlorides. Nickel with molybdenum and copper handles reducing acids such as sulphuric and phosphoric acid. Chromium handles oxidising media such as nitric acid, nitrates and oxidising salts. Molybdenum adds pitting and crevice corrosion resistance. Titanium ties up carbon, so the alloy resists intergranular attack in the as-welded condition. That is why NiCr21Mo forgings are common in welded pressure equipment.
How it compares with neighbouring grades
- Versus 316L stainless steel: far higher resistance to chloride SCC and to reducing acids, at a higher price.
- Versus Alloy 800 / 800H: similar Ni-Fe-Cr base, but the Mo, Cu and Ti additions make NiCr21Mo a corrosion alloy rather than a high-temperature alloy.
- Versus Alloy 625 or C-276: lower cost and easier to machine, but less resistant to strong oxidising chlorides and very aggressive acid concentrations.
- Versus Alloy 925 (N09925): same corrosion family, but 925 is age-hardenable and reaches far higher strength for fasteners and hangers.
NiCr21Mo chemical composition
Limits in weight percent. Molybdenum and titanium belong to this grade. A certificate without them is not NiCr21Mo.
| Element | ASTM min | ASTM max | DIN min | DIN max |
|---|---|---|---|---|
| Nickel (Ni) | 38.0 | 46.0 | 38.0 | 46.0 |
| Chromium (Cr) | 19.5 | 23.5 | 19.5 | 23.5 |
| Iron (Fe) | 22.0 | balance | 20.0 | 38.0 |
| Molybdenum (Mo) | 2.5 | 3.5 | 2.5 | 3.5 |
| Copper (Cu) | 1.5 | 3.0 | 1.5 | 3.0 |
| Titanium (Ti) | 0.6 | 1.2 | 0.6 | 1.2 |
| Carbon (C) | – | 0.05 | – | 0.025 |
| Manganese (Mn) | – | 1.0 | – | 1.0 |
| Silicon (Si) | – | 0.5 | – | 0.5 |
| Aluminium (Al) | – | 0.2 | – | 0.2 |
| Sulphur (S) | – | 0.03 | – | 0.015 |
| Phosphorus (P) | not specified | – | – | 0.02 |
| Cobalt (Co) | not specified | – | – | 1.0 |
Check limits against the governing edition of the standard on your order. Where a customer specification is tighter than the table above, we buy the billet to the tighter limits and report the actual heat analysis on the certificate.
Mechanical and physical properties
Mechanical properties of NiCr21Mo forgings
| Property | ASTM B564 minimum | Typical, forged and annealed |
|---|---|---|
| Tensile strength Rm | 586 MPa (85 ksi) | 620–760 MPa |
| Yield strength Rp0.2 | 241 MPa (35 ksi) | 260–380 MPa |
| Elongation A (4D) | 30 % | 35–50 % |
| Reduction of area | not specified | 50–70 % |
| Hardness | ≤ 22 HRC for NACE MR0175 | ≈ 130–190 HB |
Physical properties
| Property | Value |
|---|---|
| Density | 8.14 g/cm³ (0.294 lb/in³) |
| Melting range | 1370–1400 °C |
| Modulus of elasticity | ≈ 196 GPa |
| Thermal conductivity | ≈ 11.1 W/m·K |
| Mean expansion coefficient, 20–100 °C | ≈ 14.0 µm/m·K |
| Specific heat | ≈ 440 J/kg·K |
| Electrical resistivity | ≈ 1.13 µΩ·m |
| Magnetic permeability | ≈ 1.005, practically non-magnetic |
Physical values are typical for the annealed condition and are given for guidance, not as guaranteed properties.
How we forge and heat treat NiCr21Mo
The open-die route used at our Jiangyin works. Each stage is recorded against the heat number.
- MeltingEAF with AOD/VOD refining, and ESR remelting when the specification calls for it.
- Incoming checkSpectrometer analysis and PMI on every heat before the billet is cut.
- Heating1150–1180 °C, soak time matched to section thickness.
- ForgingUpset and drawn on hydraulic presses, or pierced and ring-rolled, finishing above 950 °C.
- Stabilise anneal930–980 °C, then water quench or rapid cool. NiCr21Mo is not aged.
- MachiningRough, proof or finish machining to your drawing and tolerance.
- TestingUT, PT, mechanical tests, hardness survey, PMI and corrosion testing on request.
- CertificationEN 10204 3.1 as standard, 3.2 with third-party witness, then seaworthy packing.
Heat treatment note
NiCr21Mo cannot be hardened by ageing. It is a solid-solution alloy stabilised with titanium, so the only correct heat treatment for a forging is a stabilise anneal near 940 °C followed by rapid cooling. Slow cooling through 650–760 °C allows chromium carbide precipitation at grain boundaries and reduces corrosion resistance. Higher strength comes from cold work, or from moving to the age-hardenable Incoloy 925 or Incoloy 945.
Machining and welding
NiCr21Mo work-hardens quickly. Use positive rake, rigid set-ups, slow speeds with heavy feeds and continuous cuts so the tool stays under the hardened layer. The alloy is readily welded by GTAW, GMAW and SMAW with matching ERNiFeCr-1 or ENiCrMo-3 type consumables. Because it is titanium-stabilised, post-weld heat treatment is normally not required for corrosion service.
NiCr21Mo forged products we supply
All parts are forged to drawing or to a rough size. No tooling cost and no minimum die quantity.
| Forged product | Standard size range | Typical use |
|---|---|---|
| Seamless rolled rings | OD 200–2,600 mm, height ≤ 600 mm, wall ≥ 40 mm | Vessel shell rings, bearing and gear blanks |
| Forged rings and hollow forgings | OD ≤ 2,000 mm, any wall | Body rings, spacer rings, retainers |
| Forged flanges and flange blanks | DN15–DN1200, Class 150–2500, WN, SO, BL, LJ | Piping, heat exchangers, wellhead connections |
| Round bars and shafts | Ø 60–800 mm, length ≤ 6,000 mm | Pump and agitator shafts, valve stems, spindles |
| Discs, disks and blanks | Ø ≤ 1,800 mm, thickness ≤ 600 mm | Closures, blind flanges, gear and wheel blanks |
| Sleeves and bushings | OD ≤ 1,200 mm | Wear sleeves, liners, bearing housings |
| Forged tube sheets | Ø ≤ 2,500 mm, thickness ≤ 400 mm | Shell-and-tube heat exchangers, condensers |
| Hollow bars and forged pipes | OD ≤ 900 mm, bored to drawing | Cylinders, nozzles, forged tubes |
| Blocks, cubes and valve bodies | Single-piece weight 10–8,000 kg | Valve bodies and bonnets, manifolds, seat rings |
| Shaped open-die parts | To drawing | Crankshafts, eccentric shafts, rolls, wheels, gears |
Larger or heavier pieces, and forgings in other nickel alloys, are quoted on request. Surface condition: as forged, shot blasted, pickled, rough machined or finish machined.
Where NiCr21Mo forgings are used
The grade is chosen when chlorides, acids or sour gas would attack stainless steel, but Alloy 625 or C-276 would be over-specified.
| Industry | Typical forged parts | Why NiCr21Mo |
|---|---|---|
| Oil and gas, subsea | Wellhead and Christmas-tree blocks, valve bodies and bonnets, stems, seat rings, hangers, forged flanges | Listed in NACE MR0175 / ISO 15156 for sour H₂S service |
| Chemical and petrochemical | Vessel shell rings, forged tube sheets, nozzles, manways, pump and agitator shafts | Resists sulphuric and phosphoric acid across mixed concentrations |
| Heat exchangers and pressure vessels | Tube sheets, exchanger flanges, closures, air receivers, columns and towers | Ti stabilisation keeps corrosion resistance after welding |
| Pollution control and FGD | Scrubber flanges, duct rings, spray-header parts | Handles hot chloride-bearing condensates |
| Nuclear fuel reprocessing | Nitric-acid service rings, discs and nozzles | Chromium gives resistance to oxidising acids |
| Marine and seawater | Pump shafts, sleeves, bushings, propulsion parts | High resistance to chloride pitting and SCC |
| Pulp, paper and food | Digester parts, rolls, agitator shafts | Clean, non-contaminating and weld-repairable |
| Pickling and acid regeneration | Tank flanges, forged pipes, valve parts | The copper addition improves reducing-acid performance |
Testing, inspection and certification
Non-destructive testing
Ultrasonic testing to EN 10228-4 for austenitic forgings, ASTM A388 or SEP 1921, to the acceptance class on your order. Penetrant testing to ASTM E165 or ASME V Article 6.
Chemistry and PMI
Heat analysis by optical emission spectrometry, plus positive material identification on finished parts, so a NiCr21Mo forging is never confused with a stainless one.
Mechanical testing
Tensile, impact, hardness survey and grain size to the standard on your order, with test blocks heat treated together with the forgings.
Corrosion testing
Intergranular corrosion testing to ASTM G28 Method A or ASTM A262 where the specification requires it.
Certification
EN 10204 3.1 as standard. EN 10204 3.2 witnessed by TÜV, BV, DNV, LR or SGS on request, with full heat-treatment charts.
Traceability
Heat number hard-stamped or vibro-etched on every piece and cross-referenced to the mill certificate and the forging record.
How to order NiCr21Mo forgings
Send a drawing, or the rough dimensions, to sales@steelforgepieces.com. A quotation normally comes back within one working day.
What to include in your enquiry
- Grade as you want it written on the certificate: NiCr21Mo, 2.4858, UNS N08825 or Alloy 825
- Drawing or rough size, and whether you want as-forged, rough machined or finish machined
- Quantity, including one-off and prototype pieces
- Governing specification (ASTM B564, NACE MR0175, client spec) and any tighter chemistry limits
- NDT requirement and acceptance class, and certificate type (EN 10204 3.1 or 3.2)
- Destination port and Incoterm: EXW, FOB Shanghai or Ningbo, CIF or DDP
Typical lead time for open-die NiCr21Mo forgings is 25 to 45 days from order confirmation, depending on billet availability and the amount of machining. Parts are packed in fumigation-free plywood cases suitable for sea freight.
Frequently asked questions about NiCr21Mo
What is NiCr21Mo?
NiCr21Mo is the EN/DIN short name for the titanium-stabilised nickel-iron-chromium alloy with molybdenum and copper covered by Werkstoff number 2.4858 and UNS N08825, sold commercially as Alloy 825. It contains 38–46 % nickel, 19.5–23.5 % chromium, 2.5–3.5 % molybdenum, 1.5–3.0 % copper and at least 22 % iron.
Is NiCr21Mo the same material as Incoloy 825?
Yes. NiCr21Mo, 2.4858, UNS N08825, BS NA16 and Alloy 825 all describe the same alloy, and Incoloy 825 is the trade name registered by Special Metals Corporation for that grade. A forging ordered as NiCr21Mo and one ordered as Alloy 825 are metallurgically identical.
Can NiCr21Mo forgings be hardened by heat treatment?
No. NiCr21Mo is a solid-solution alloy and is not age-hardenable. The correct treatment for a forging is a stabilise anneal near 940 °C followed by rapid cooling, which restores ductility and corrosion resistance. Strength is increased by cold work, or by choosing an age-hardenable grade such as Incoloy 925.
What is the maximum service temperature of NiCr21Mo?
In corrosive service the alloy is normally limited to about 540 °C. Above that, titanium stabilisation no longer reliably prevents carbide precipitation and corrosion resistance falls. For higher temperatures use Alloy 800H, Alloy 625 or Alloy 617.
Which standards apply to NiCr21Mo forgings?
Forgings and forged fittings are ordered to ASTM B564 or ASME SB-564. Bar is ASTM B425, plate ASTM B424, seamless tube ASTM B423 and fittings ASTM B366. The European composition is DIN 17744. For sour service the alloy appears in NACE MR0175 / ISO 15156 and API 6CRA.
Is NiCr21Mo suitable for sour service with H₂S?
Yes. UNS N08825 is a listed corrosion-resistant alloy in NACE MR0175 / ISO 15156 for wellhead and downhole components, within the hardness and environmental limits given in that standard. Its high nickel content also resists chloride stress corrosion cracking.
What is the minimum order quantity?
Jiangyin Jiangnan Metal Co., Ltd. accepts single pieces, prototypes and production batches, because every part is open-die forged to drawing rather than pressed in dedicated dies. There is no tooling charge.
What documents come with the forgings?
Every shipment carries an EN 10204 3.1 certificate showing heat number, chemical analysis, mechanical results and heat-treatment records. EN 10204 3.2 witnessed by TÜV, BV, DNV, LR or SGS is available, along with ultrasonic and penetrant reports and PMI records.
Source, review and citation
Cite this page
“NiCr21Mo (Alloy 825 / UNS N08825 / W.Nr. 2.4858) forging data.” Jiangyin Jiangnan Metal Co., Ltd., Jiangyin, Jiangsu, China. https://www.steelforgepieces.com/Nickel-Alloy/NiCr21Mo.html
This page is written and maintained by the forging and metallurgy team at Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. Composition and property data are taken from ASTM B425, ASTM B564 and DIN 17744 together with our own production and test records. Check all values against the governing edition of the standard before using them in a design calculation.
Last reviewed and updated: · sales@steelforgepieces.com · 0086-189-2135-9659
Request a NiCr21Mo quotation
Send a drawing or the rough size. We quote the forging, heat treatment, machining and certificate as one price.
ManufacturerJiangyin Jiangnan Metal Co., Ltd., open-die forging factory
AddressNo.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
Phone and WhatsApp0086-189-2135-9659
Emailsales@steelforgepieces.com