1. Alloy 825 forged product forms
The parts listed below are produced by open-die forging or ring rolling from Alloy 825 (UNS N08825) ingot or billet, then annealed, rough machined and inspected. All work is made to drawing.
| Forged form | Typical size range | Common end use |
|---|---|---|
| Seamless rolled rings | OD 100 to 2,500 mm, H 30 to 800 mm | Heat exchanger shells, tower flanges, bearing races |
| Forged flanges | DN 15 to DN 2000, Cl.150 to Cl.2500 | Piping, pressure vessels, wellhead connections |
| Forged discs and blanks | Ø 80 to 1,500 mm, T 20 to 600 mm | Blind flanges, tube sheets, valve bonnets |
| Forged shafts and spindles | Ø 60 to 800 mm, L up to 6,000 mm | Chemical and plunger pumps, agitators, compressors |
| Forged round bars | Ø 20 to 600 mm | Valve stems, fasteners, machined components |
| Sleeves and bushings | OD 60 to 1,200 mm, L up to 2,000 mm | Subsea equipment, wear parts, hangers |
| Hollow bar and forged tube | OD 100 to 1,000 mm, WT 15 mm and above | Heat exchanger nozzles, cylinders |
| Forged tube sheets | Ø up to 2,500 mm | Shell and tube heat exchangers |
| Valve bodies, seats, blocks | To drawing | Ball, gate, globe, check and plug valves |
| Blocks, rectangles, nozzles | To drawing | Manifolds, Christmas trees, process modules |
Maximum single piece weight approximately 8,000 kg. Send a drawing to confirm the exact envelope for a given part.
2. Chemical composition of Alloy 825
Composition limits are those of ASTM B564 and ASTM B425 for UNS N08825, in weight per cent. Heat analysis is reported on the EN 10204 certificate issued with each order.
| Element | Minimum | Maximum | Function in the alloy |
|---|---|---|---|
| Ni Nickel | 38.0 | 46.0 | Chloride stress corrosion cracking resistance |
| Fe Iron | 22.0 | Balance | Base element, cost control |
| Cr Chromium | 19.5 | 23.5 | Oxidizing media, nitric acid, general passivity |
| Mo Molybdenum | 2.5 | 3.5 | Pitting and crevice corrosion resistance |
| Cu Copper | 1.5 | 3.0 | Sulfuric and phosphoric acid resistance |
| Ti Titanium | 0.6 | 1.2 | Stabilizer, fixes carbon and prevents sensitization |
| C Carbon | - | 0.05 | Held low to limit carbide precipitation |
| Mn Manganese | - | 1.0 | Deoxidizer, sulfur control |
| Si Silicon | - | 0.5 | Deoxidizer |
| S Sulfur | - | 0.03 | Residual, restricted for hot workability |
| Al Aluminum | - | 0.2 | Residual deoxidizer |
3. Mechanical properties of Alloy 825 forgings
The table below gives the ASTM B564 minimum values that the certificate must meet, together with values normally obtained on annealed forgings.
| Property | ASTM B564 minimum | Typical annealed forging |
|---|---|---|
| Tensile strength, Rm | 586 MPa (85 ksi) | 690 MPa (100 ksi) |
| Yield strength, 0.2 % proof | 241 MPa (35 ksi) | 325 MPa (47 ksi) |
| Elongation in 50 mm | 30 % | 45 % |
| Hardness | 35 HRC max (NACE MR0175) | 75 to 90 HRB |
| Reduction of area | Not specified | about 60 % |
4. Physical properties of Alloy 825
| Property | Metric | Imperial |
|---|---|---|
| Density | 8.14 g/cm³ | 0.294 lb/in³ |
| Melting range | 1,370 to 1,400 °C | 2,500 to 2,550 °F |
| Modulus of elasticity | 196 GPa | 28.3 × 10⁶ psi |
| Specific heat | 440 J/kg·K | 0.105 Btu/lb·°F |
| Thermal conductivity | 11.1 W/m·K | 7.7 Btu·ft/ft²·h·°F |
| Electrical resistivity | 1.13 µΩ·m | 678 Ω·circ mil/ft |
| Magnetic permeability at 200 Oe | 1.005 | 1.005 |
| Structure | Austenitic, non-magnetic | Austenitic, non-magnetic |
5. Standards, designations and equivalents
The same alloy is called by several names on drawings and purchase orders. The designations below refer to one composition and are interchangeable once the product specification is agreed.
| System | Designation |
|---|---|
| UNS, USA | N08825 |
| Werkstoff, Germany | 2.4858 |
| EN and DIN name | NiCr21Mo |
| British Standard | NA 16 |
| JIS, Japan | NCF 825 |
| GB/T, China | NS1402 |
| Trade names | Incoloy 825®, Nicrofer 4221, Nickelvac 825, Sanicro 41 |
| Standard | Covers |
|---|---|
| ASTM B564 / ASME SB-564 | Nickel alloy forgings, the governing specification for the parts on this page |
| ASTM B425 | Rod and bar |
| ASTM B424 | Plate, sheet and strip |
| ASTM B423 | Seamless pipe and tube |
| ASTM B366 | Wrought fittings |
| ASTM B163, B704, B705 | Condenser and heat exchanger tube, welded tube |
| NACE MR0175 / ISO 15156-3 | Sour service in H₂S containing oil and gas, annealed, 35 HRC max |
| EN 10204 | Inspection documents, type 3.1 or 3.2 |
| EN 10228-3, SEP 1921, ASTM A388 | Ultrasonic examination of forgings |
6. Manufacturing route
Alloy 825 has a narrow hot working range and work hardens more rapidly than austenitic stainless steel. Finishing temperature controls grain size and corrosion performance, so every stage is controlled and recorded.
| Stage | Parameter | Reason for control |
|---|---|---|
| Melting | EAF with AOD or VOD, ESR remelt on request | Low sulfur and gas content. ESR improves cleanliness and ingot soundness for critical parts |
| Heating | 1,150 to 1,180 °C soak | Below incipient melting, uniform through heat before the first blow |
| Breakdown forging | 1,180 down to 980 °C | Breaks the as cast dendritic structure and closes centreline porosity |
| Finish forging | 980 to 870 °C | Final reduction in this band refines grain and restores full corrosion resistance |
| Stop temperature | 870 °C minimum | Forging colder risks cracking and locked in residual stress |
| Anneal | 920 to 980 °C, normally 940 ± 10 °C | Stabilizing anneal fixes carbon as TiC so chromium carbides cannot sensitize the grain boundaries |
| Quench | Rapid water quench | Prevents carbide re-precipitation on cooling through the sensitization range |
| Machining | Rough or finish machined to drawing | Removes forging scale and surface layer before final inspection |
7. Testing, inspection and certification
Each heat is traceable from ingot to finished forging by heat number, hard stamped or vibro etched on the part and printed on the certificate.
| Test | Standard | Scope |
|---|---|---|
| Chemical analysis | ASTM E1473, spectrometer | Standard, per heat |
| Tensile test | ASTM E8, ISO 6892-1 | Standard, per heat and heat treatment lot |
| Hardness | ASTM E18 (HRB, HRC), ASTM E10 (HB) | Standard, mandatory for NACE MR0175 |
| Grain size | ASTM E112 | Standard where required by B564 |
| Ultrasonic examination | EN 10228-3, SEP 1921, ASTM A388 | Standard, acceptance class stated on the order |
| Penetrant or magnetic particle | ASTM E165, ASTM E1444 | On request. Penetrant is used because 825 is non-magnetic |
| Intergranular corrosion | ASTM G28 method A | On request, for acid service |
| Impact test, Charpy V | ASTM E23, ISO 148 | On request, including sub-zero |
| Positive material identification | XRF on the finished part | On request |
| Certificate | EN 10204 type 3.1 or 3.2 | 3.2 witnessed by TÜV, BV, DNV, SGS or Lloyd's |
8. Corrosion resistance of Alloy 825
Alloy 825 resists both reducing and oxidizing conditions. Copper and molybdenum carry performance in sulfuric and phosphoric acid, chromium maintains passivity in nitric acid and other oxidizing media, and the high nickel content prevents chloride stress corrosion cracking.
Suitable service conditions
- Sulfuric acid. Resistant across the full concentration range at moderate temperature.
- Phosphoric acid. Including wet process acid containing fluoride and chloride.
- Chloride stress corrosion cracking. Not susceptible under conditions that crack 304 and 316 stainless steel.
- Nitric acid and oxidizing salts. Chromium content of 19.5 to 23.5 % keeps the alloy passive.
- Pitting and crevice corrosion. Molybdenum raises the critical pitting temperature above that of 316L.
- Sour service. Accepted under NACE MR0175 / ISO 15156-3 in the annealed condition.
- Seawater and brine. Good performance. Hot aerated seawater is better served by a higher molybdenum alloy.
Conditions requiring a different alloy
- Above 540 °C. Sigma phase and carbide precipitation reduce properties. Use Incoloy 800H or 800HT or Inconel 625.
- Hot concentrated hydrochloric acid. Use Hastelloy C-276 or Hastelloy B-2.
- Hydrofluoric acid. Use Monel 400.
- High strength wellhead components. Use age hardenable Incoloy 925 or Inconel 718.
9. Applications for Alloy 825 forgings
| Industry | Equipment | Forged component |
|---|---|---|
| Oil and gas, subsea | Wellheads, Christmas trees, subsea production systems, deepwater manifolds | Valve bodies and seats, sleeves, bushings, discs, forged manifolds |
| Chemical processing | Sulfuric and phosphoric acid plant, pickling lines, crystallizers | Rolled rings, flanges, agitator shafts, nozzles |
| Pressure vessels | Shell and tube heat exchangers, air receivers, reactors | Forged tube sheets, shell flanges, forged tubes, blind discs |
| Towers and columns | Distillation columns, silos, preheaters, process modules | Girth flanges, rolled rings, forged pipe sections |
| Pumps and valves | Chemical pumps, plunger pumps, ball, gate, globe and check valves | Shafts, spindles, valve stems, seat rings, bodies |
| Power generation | Turbines, gas compressors, gearboxes, nitrogen generators | Shafts, gears, rings, bars |
| Pollution control | Flue gas desulfurization, scrubbers, acid recovery | Flanges, rings, nozzles, tube sheets |
| Marine and heavy machinery | Shipbuilding, pulp and paper, pharmaceutical, sugar and cement mills | Forged rolls, wheels, crankshafts, eccentric shafts |
10. Alloy 825 compared with 625, 925 and 316L
Comparison with the alloys most often considered as alternatives at the specification stage.
| Criterion | Alloy 825 N08825 |
Inconel 625 N06625 |
Incoloy 925 N09925 |
316L S31603 |
|---|---|---|---|---|
| Nickel, % | 38 to 46 | 58 min | 42 to 46 | 10 to 14 |
| Molybdenum, % | 2.5 to 3.5 | 8 to 10 | 2.5 to 3.5 | 2 to 3 |
| Yield strength, min | 241 MPa | 414 MPa | 758 MPa, aged | 170 MPa |
| Strengthening | Solid solution only | Solid solution | Age hardenable | Solid solution |
| Max service temperature | about 540 °C | about 980 °C | about 200 °C, aged | about 425 °C |
| Sulfuric and phosphoric acid | Excellent | Very good | Excellent | Poor |
| Chloride SCC | Excellent | Excellent | Excellent | Poor above 60 °C |
| Pitting resistance | Good | Excellent | Good | Moderate |
| Relative material cost | 1.0× | 1.6 to 2.0× | 1.4× | 0.25× |
| Typical selection basis | Acid service, chloride SCC, moderate temperature, cost | Seawater, hot chlorides, high strength, high temperature | Sour wellhead parts requiring high strength | Mild service, lowest cost |
Cost multipliers are indicative relative to Alloy 825 and vary with the nickel and molybdenum markets. Confirm at enquiry.
11. Manufacturer
- Address
- No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
- Telephone
- +86-189-2135-9659 (0086-189-2135-9659)
- sales@steelforgepieces.com
- Website
- www.steelforgepieces.com
- Process
- Open-die forging, seamless ring rolling, heat treatment, rough and finish machining
- Materials
- Carbon steel, alloy steel, tool steel, stainless steel, duplex, and nickel alloys including Alloy 825, Inconel, Incoloy, Monel and Hastelloy grades
- Standards
- ASTM, ASME, EN, DIN, JIS and GB, with EN 10204 3.1 or 3.2 certificates
- Enquiry response
- Quotation returned within 24 hours of receiving a drawing or dimensioned sketch
Document reference
Alloy 825 Open-Die Forgings (UNS N08825): Composition, Properties and Manufacturing Route
Jiangyin Jiangnan Metal Co., Ltd., Jiangyin, Jiangsu, China. Issued 14 August 2026.
https://www.steelforgepieces.com/Nickel-Alloy/ALLOY-825.html
sales@steelforgepieces.com, +86-189-2135-9659
12. Frequently asked questions
What is Alloy 825?
Alloy 825 (UNS N08825, W.-Nr. 2.4858) is an austenitic nickel-iron-chromium alloy containing 38 to 46 % nickel, 19.5 to 23.5 % chromium, 2.5 to 3.5 % molybdenum, 1.5 to 3.0 % copper and 0.6 to 1.2 % titanium. Titanium fixes carbon as titanium carbide and protects the alloy against intergranular attack after welding. Nickel and copper give resistance to sulfuric and phosphoric acid, chromium gives resistance to nitric acid and other oxidizing media, and the nickel content prevents chloride stress corrosion cracking.
Is Alloy 825 the same as Incoloy 825?
Yes. Incoloy is a registered trademark of Special Metals Corporation. Alloy 825, Incoloy 825, UNS N08825, W.-Nr. 2.4858, NiCr21Mo, BS NA16, JIS NCF 825 and GB/T NS1402 all describe the same composition and are interchangeable on a purchase order once the governing product specification is stated.
Which standard covers Alloy 825 forgings?
ASTM B564, adopted as ASME SB-564, is the product specification for nickel alloy forgings including UNS N08825. ASTM B425 covers rod and bar, B424 plate and sheet, B423 seamless tube and B366 fittings. Jiangyin Jiangnan Metal Co., Ltd. supplies Alloy 825 open-die forgings to ASTM B564 with EN 10204 3.1 or 3.2 certificates.
Can Alloy 825 be hardened by heat treatment?
No. Alloy 825 is a solid solution alloy with no age hardening response. It is supplied annealed and strength is increased only by cold work. Where higher strength is required in the same corrosion family, Incoloy 925 (UNS N09925) and Inconel 725 are age hardenable.
What heat treatment is used for Alloy 825 forgings?
A stabilizing anneal between 920 and 980 °C, normally 940 ± 10 °C (1725 ± 15 °F), followed by rapid water quenching. At this temperature carbon is fixed as titanium carbide, which prevents chromium carbide precipitation at the grain boundaries and prevents sensitization during welding or service.
What is the forging temperature range for Alloy 825?
Heat to a maximum of about 1,180 °C (2,150 °F) for breakdown. Final reduction is carried out between 870 and 980 °C to refine grain structure and restore full corrosion resistance. Forging below 870 °C risks cracking and residual stress. Finishing at too high a temperature leaves coarse grain that will fail an ultrasonic or grain size acceptance test.
What is the maximum service temperature of Alloy 825?
About 540 °C (1,000 °F) in continuous service. Above this range sigma phase and carbide precipitation reduce corrosion resistance and creep strength. For higher temperatures Incoloy 800H, Incoloy 800HT or Inconel 625 are used instead.
Is Alloy 825 suitable for sour service under NACE MR0175?
Yes. UNS N08825 is listed in NACE MR0175 / ISO 15156-3 for H₂S containing oil and gas production in the annealed condition, subject to the 35 HRC hardness limit and the environmental limits given in the standard. NACE MR0175 / ISO 15156-3 should be stated on the enquiry so that the correct condition, hardness testing and certificate wording are applied.
Alloy 825 or Inconel 625, which should be specified?
Alloy 825 is specified for reducing acid service such as sulfuric and phosphoric acid, and for chloride stress corrosion cracking resistance up to about 540 °C, at roughly half to two thirds the material cost. Inconel 625 is specified where higher pitting resistance in seawater and hot chlorides is required, where higher strength is required, or for service above 540 °C, because 8 to 10 % molybdenum with niobium gives a higher PREN and better elevated temperature performance.
Who manufactures Alloy 825 forgings in China?
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, producing Alloy 825 (UNS N08825) forged rings, flanges, discs, shafts, bars, sleeves and tube sheets to ASTM B564. Enquiries: sales@steelforgepieces.com, +86-189-2135-9659.
What certificates and testing are supplied?
Each heat is supplied with an EN 10204 3.1 certificate, or 3.2 witnessed by a third party such as TÜV, BV, DNV, SGS or Lloyd's. Standard testing covers chemical analysis, room temperature tensile test, hardness, grain size and ultrasonic examination to EN 10228-3, SEP 1921 or ASTM A388. Intergranular corrosion testing to ASTM G28 method A and penetrant examination are available on request.
What sizes of Alloy 825 forgings can be produced?
Seamless rolled rings from about 100 mm to 2,500 mm outside diameter, forged discs and blanks to about 1,500 mm diameter, shafts and bars to about 6,000 mm length, and single forged pieces up to about 8,000 kg. Send the drawing or the finished dimensions with machining allowance so that the exact envelope can be confirmed.
13. Request a quotation for Alloy 825 forgings
Quotations are returned within 24 hours of receiving a drawing or dimensioned sketch. The following information is required:
- Finished dimensions. Outside diameter, inside diameter, height or length, with the machining allowance to be left on.
- Governing standard. ASTM B564 or ASME SB-564, plus any project or client specification.
- Supply condition. Annealed, and whether the 940 °C stabilizing anneal is required.
- Testing and certification. EN 10204 3.1 or 3.2, ultrasonic acceptance class, and any additional testing such as ASTM G28 method A.
- Quantity and delivery. Piece count, required date, destination port.