# NC21FeDU Forgings (Alloy 825 / UNS N08825 / W.Nr. 2.4858 / NiCr21Mo / NA16)

Source: https://www.steelforgepieces.com/Nickel-Alloy/NC21FeDU.html
Publisher: Jiangyin Jiangnan Metal Co., Ltd., open-die forging factory
Updated: 22 August 2026

NC21FeDU is the AFNOR (French) designation for a nickel-iron-chromium-molybdenum-copper alloy.
The same material carries the numbers UNS N08825, W.Nr. 2.4858 (NiCr21Mo) and BS NA16, and is
sold under the trade name Incoloy 825. Nominal composition is 42% nickel, 22% chromium,
3% molybdenum and 2% copper, stabilised with titanium. It resists sulfuric and phosphoric acid,
chloride stress-corrosion cracking, pitting and intergranular attack, in both oxidising and
reducing conditions.

Jiangyin Jiangnan Metal Co., Ltd. forges NC21FeDU at its works at No.1 Chengxiqiao Road,
Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. Available forms are seamless rolled
rings, flanges, shafts, round bars, discs, sleeves, bushings, tube sheets and hollow forged pipe,
in single-piece weights from about 5 kg up to 15 tonnes. Material is melted by EAF plus AOD or
VOD, with an ESR remelt where the specification asks for one, supplied solution annealed,
ultrasonically tested to EN 10228-3, SEP 1921 or ASTM A388, and certified to EN 10204 3.1 or 3.2.
Enquiries: sales@steelforgepieces.com, +86 189 2135 9659.

## At a glance

| | |
|---|---|
| Grade | NC21FeDU, also written NC21FeDu |
| UNS | N08825 |
| Werkstoff | 2.4858, NiCr21Mo |
| Alloy family | Ni-Fe-Cr-Mo-Cu, austenitic, titanium stabilised, solid solution strengthened |
| Forging spec | ASTM B564 / ASME SB-564 |
| Condition | Solution annealed. Not age hardenable |
| Density | 8.14 g/cm3 |
| Certification | EN 10204 3.1 as standard, 3.2 third party on request |

## What NC21FeDU is

NC21FeDU is fully austenitic, and each of its main additions does a specific job. The nickel
content puts it well outside the range where 300 series stainless steels crack in hot chlorides.
Chromium covers oxidising media such as nitric acid. Molybdenum and copper together give the alloy
its resistance to reducing acids, sulfuric and phosphoric in particular, and the copper is the
reason NC21FeDU handles sulfuric acid better than most other nickel grades. Titanium ties up
carbon so the alloy does not sensitise during welding or hot working, which keeps it resistant to
intergranular attack without a post-weld heat treatment.

Strength comes from solid solution rather than from precipitation. Proof stress in the annealed
condition is therefore modest, 241 MPa minimum, but ductility and toughness are high and the alloy
takes heavy hot reduction without cracking. In a forging shop that matters, and it is why NC21FeDU
turns up in heavy single-piece parts for acid plant and wellhead equipment rather than just in
sheet and tube.

## Equivalent designations and standards

| Standards body or country | Designation |
|---|---|
| AFNOR, France | NC21FeDU |
| UNS, USA | N08825 |
| Werkstoff and DIN, Germany | 2.4858, NiCr21Mo |
| EN | NiCr21Mo |
| BS, UK | NA16 |
| JIS, Japan | NCF 825 |
| GB, China | NS142 |
| Trade names | Incoloy 825, Nicrofer 4221, Alloy 825 |
| ASTM and ASME, forgings | B564 / SB-564 |
| ASTM and ASME, rod and bar | B425 / SB-425 |
| ASTM and ASME, plate sheet strip | B424 / SB-424 |
| ASTM and ASME, seamless tube and pipe | B423, B163 / SB-423, SB-163 |
| Sour service | Listed in NACE MR0175 and ISO 15156-3 within the limits of that standard |

## Chemical composition

Weight percent. ASTM B564 and B425 for UNS N08825, with DIN 17744 limits where they differ.

| Element | Symbol | ASTM B564 / B425 | DIN 17744 (2.4858) |
|---|---|---|---|
| Nickel | Ni | 38.0 to 46.0 | 38.0 to 46.0 |
| Chromium | Cr | 19.5 to 23.5 | 19.5 to 23.5 |
| Iron | Fe | 22.0 min | Balance, about 30 |
| Molybdenum | Mo | 2.5 to 3.5 | 2.5 to 3.5 |
| Copper | Cu | 1.5 to 3.0 | 1.5 to 3.0 |
| Titanium | Ti | 0.6 to 1.2 | 0.6 to 1.2 |
| Carbon | C | 0.05 max | 0.025 max |
| Manganese | Mn | 1.0 max | 1.0 max |
| Silicon | Si | 0.5 max | 0.5 max |
| Aluminium | Al | 0.2 max | 0.2 max |
| Sulfur | S | 0.03 max | 0.015 max |
| Phosphorus | P | Not specified | 0.02 max |
| Cobalt | Co | Not specified | 1.0 max |

If your project specification calls for the tighter DIN carbon and sulfur limits, say so on the
enquiry. The heat has to be picked before forging starts, not after.

## Mechanical properties, solution annealed, room temperature

| Property | Metric | Imperial | Basis |
|---|---|---|---|
| Tensile strength Rm | 586 MPa min | 85 ksi min | ASTM B564 / B425 |
| Yield strength Rp0.2 | 241 MPa min | 35 ksi min | ASTM B564 / B425 |
| Elongation A | 30% min | 30% min | ASTM B564 / B425 |
| Reduction of area Z | 40% typical | 40% typical | Typical, not a spec requirement |
| Hardness | 90 HRB max typical | about 120 to 180 HB | Typical, annealed |
| Impact KV at 20 C | 100 J typical | 74 ft-lb typical | Typical, tested on request |

Values are specification minimums. Actual figures for your parts are reported on the mill test
certificate against the heat number.

## Physical properties at 20 C

| Property | Value |
|---|---|
| Density | 8.14 g/cm3 (0.294 lb/in3) |
| Melting range | 1370 to 1400 C (2500 to 2550 F) |
| Modulus of elasticity | 196 GPa (28.4 x 10^6 psi) |
| Thermal conductivity | 11.1 W/m.K |
| Mean thermal expansion, 20 to 100 C | 14.0 um/m.K |
| Specific heat | 440 J/kg.K |
| Electrical resistivity | 1.13 uohm.m |
| Relative magnetic permeability | about 1.005, effectively non-magnetic |
| Curie temperature | below -110 C |

## Corrosion behaviour

- Sulfuric acid. Resists all concentrations up to moderate temperatures. The copper addition is what makes this possible.
- Phosphoric acid. A standard choice for wet process phosphoric acid evaporators and heat exchangers.
- Chloride stress-corrosion cracking. At around 42% nickel the alloy sits well clear of the range where 300 series stainless steels fail.
- Pitting and crevice corrosion. Molybdenum and chromium give it a clear margin over 316L in chloride bearing media.
- Intergranular corrosion. Titanium stabilisation prevents chromium carbide sensitisation, verified by ASTM A262 or ASTM G28 when the order calls for it.
- Seawater and brine. Used for propeller shafts, tank truck linings and marine heat exchange duty.
- Where it does not suit. Hot concentrated oxidising acids such as boiling nitric, and sustained service above about 540 C.

## Forging and heat treatment

### Melting

Material is melted by electric arc furnace with AOD or VOD refining. An electroslag remelt is
added where the specification calls for better cleanliness, tighter segregation control or a
higher ultrasonic acceptance class. Sour service parts and rotating parts usually fall in that
group.

### Hot working

- Heat uniformly to 1150 to 1180 C and soak long enough for the section to equalise.
- Work down through 1180 to 900 C. Reheat rather than carry on below the finishing temperature.
- Do not finish below about 870 C. Light reductions at low temperature produce duplex grain structure and ultrasonic noise, and both show up later at inspection.
- Put real reduction on the final heat. A high forging ratio is the only way to refine grain in an alloy that has no phase transformation to do it instead.

### Heat treatment

NC21FeDU is not age hardenable. Its titanium is there to stabilise the alloy against carbide
sensitisation, not to form gamma prime, so a solution plus ageing cycle of the sort used on
Inconel 718 or Incoloy 925 will not raise its strength. A drawing that calls for one usually means
the grade was substituted somewhere upstream, and it is worth checking back before anything goes
under the hammer. The correct final condition is:

- Solution or stabilising anneal at 930 to 980 C, hold according to section thickness, then water quench or rapid air cool.
- Fast cooling through the sensitisation range is what preserves corrosion resistance.
- Where the highest resistance to intergranular attack is required, anneal at the top of the range and verify by ASTM G28 method A.

If your design needs more strength in the same corrosion family, specify Incoloy 925 or
Incoloy 945. Those two are genuinely precipitation hardenable.

## Forged forms and size envelope

Indicative open-die capability. The envelope confirmed for your part is stated on the quotation.

| Forged form | Indicative size range |
|---|---|
| Seamless rolled rings | OD 200 to 3000 mm, height up to 800 mm |
| Forged flanges | OD 100 to 2500 mm |
| Discs and disks | OD up to 2500 mm, thickness up to 600 mm |
| Shafts, spindles, round bars | Dia. 60 to 800 mm, length up to 6000 mm |
| Sleeves and bushings | OD up to 1200 mm |
| Tube sheets | OD up to 3000 mm |
| Forged tubes and hollow pipe | OD up to 1200 mm |
| Valve bodies, blocks, seat rings, nozzles | To customer drawing |
| Single-piece weight | 5 kg to 15 000 kg |

Supplied as forged, rough machined or finish machined to drawing. Tolerances, machining allowance
and surface condition are agreed at quotation stage.

## Where NC21FeDU forgings are used

- Chemical and acid processing. Phosphoric acid evaporators, sulfuric acid handling, pickling tanks and baskets, reactor internals, columns, towers, silos and preheaters.
- Oil, gas and offshore. Wellhead and Christmas tree components, subsea and deepwater production hardware, tubing hangers, valve blocks and bodies for sour service.
- Pressure vessels and heat exchange. Forged tube sheets, shell and tube exchanger components, air receivers, nozzles and flanges for corrosive duty.
- Valves and flow control. Ball, gate, globe, check and plug valve bodies, stems, seat rings and strainer components.
- Rotating equipment. Chemical pump and plunger pump shafts, propeller shafts, compressor components, gearbox parts and rolled rings for power transmission.
- Pollution control and nuclear. Flue gas desulfurisation scrubbers, waste processing equipment and hardware for spent nuclear fuel recovery.

## Testing, NDT and certification

- Ultrasonic testing. EN 10228-3, SEP 1921 or ASTM A388, at the class stated on the order.
- Surface NDT. Liquid penetrant to ASTM E165 or EN 571. Magnetic particle does not apply here, the alloy is non-magnetic.
- Chemical analysis. Spectrometric analysis per heat, plus positive material identification on finished parts when required.
- Mechanical testing. Tensile and hardness as standard. Charpy impact and elevated temperature tensile on request.
- Corrosion testing. ASTM G28 method A or ASTM A262 practice C where intergranular resistance has to be demonstrated.
- Grain size and microstructure. ASTM E112, reported when specified.
- Certification. EN 10204 3.1 as standard. EN 10204 3.2 witnessed by TUV, BV, SGS, DNV or Lloyd's Register on request.

## About the works

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging manufacturer at No.1 Chengxiqiao Road,
Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, inside the Yangtze River Delta forging
cluster and about two hours from the ports of Shanghai and Ningbo. We produce open-die forgings
and seamless rolled rings in carbon steel, alloy steel, tool steel, stainless steel and nickel
alloys, for pressure vessel, valve, oil and gas, power generation, marine and heavy machinery
customers.

NC21FeDU parts are made to drawing, not taken off a shelf. The forging route, the heat treatment
and the inspection plan are all set against your governing specification before production starts,
and written into the order.

## Request a quotation

Send us the following and a quotation normally goes back within one working day. Single-piece and
prototype orders are accepted.

- Drawing, sketch, or rough dimensions, plus the quantity
- Governing specification, for example ASTM B564 UNS N08825, and the delivery condition
- Required NDT class and certification level, EN 10204 3.1 or 3.2
- Any project or end user requirement such as NACE MR0175 and ISO 15156

Email: sales@steelforgepieces.com
Telephone: +86 189 2135 9659

## Frequently asked questions

**What is NC21FeDU?**
NC21FeDU is the AFNOR (French) designation for a nickel-iron-chromium-molybdenum-copper alloy
containing nominally 42% nickel, 22% chromium, 3% molybdenum and 2% copper, stabilised with
titanium. The same material carries the numbers UNS N08825, W.Nr. 2.4858 and BS NA16, and is sold
under the trade name Incoloy 825.

**What is NC21FeDU equivalent to?**
UNS N08825 in the USA, W.Nr. 2.4858 and NiCr21Mo in Germany and EN, NA16 in the UK, NCF 825 in
Japan, NS142 in China, and the trade names Incoloy 825 and Nicrofer 4221. Forgings are ordered to
ASTM B564 or ASME SB-564, bar to ASTM B425.

**Is NC21FeDU the same as Incoloy 825?**
Yes. Incoloy 825 is a trade name for the alloy whose French designation is NC21FeDU and whose UNS
number is N08825. Chemistry, properties and applications are identical, so material ordered as
NC21FeDU can be supplied and certified against ASTM B564 UNS N08825.

**What is the chemical composition of NC21FeDU?**
Per ASTM B564 and B425 for UNS N08825: nickel 38.0 to 46.0%, chromium 19.5 to 23.5%, iron 22.0%
min, molybdenum 2.5 to 3.5%, copper 1.5 to 3.0%, titanium 0.6 to 1.2%, carbon 0.05% max, manganese
1.0% max, silicon 0.5% max, sulfur 0.03% max, aluminium 0.2% max. DIN 17744 tightens carbon to
0.025% max and sulfur to 0.015% max, and adds cobalt 1.0% max and phosphorus 0.02% max.

**Can NC21FeDU be age hardened?**
No. It is strengthened by solid solution and stabilised with titanium. The titanium ties up carbon
to prevent sensitisation, it does not form a strengthening precipitate, so ageing will not raise
the strength. The correct final treatment is a solution or stabilising anneal at 930 to 980 C
followed by rapid cooling. Where higher strength is needed in the same corrosion family, specify
Incoloy 925 or Incoloy 945.

**What is the maximum service temperature of NC21FeDU?**
Around 540 C for corrosion service. Long exposure between roughly 650 and 760 C can cost corrosion
resistance and toughness. For continuous higher temperature duty, look at Incoloy 800H,
Incoloy 800HT or Inconel 625.

**Is NC21FeDU magnetic?**
No. In the annealed condition the structure is austenitic and the alloy is effectively
non-magnetic at room temperature, with relative permeability around 1.005. That is also why
magnetic particle inspection does not apply and penetrant testing is used instead.

**Is NC21FeDU acceptable for sour service?**
UNS N08825 is listed in NACE MR0175 and ISO 15156-3 for sour service within the environmental and
hardness limits given in that standard. The permitted envelope depends on product form, condition,
H2S partial pressure, chloride level, pH and temperature, so it has to be confirmed against the
standard for each application.

**What forged shapes are available in NC21FeDU?**
Seamless rolled rings, flanges, shafts, round bars, discs and disks, sleeves, bushings, tube
sheets, forged tubes and pipe, valve bodies, seat rings, nozzles, manifolds and custom forgings to
drawing, in single-piece weights from about 5 kg to 15 tonnes.

**Who supplies NC21FeDU open-die forgings?**
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road,
Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, manufacturing NC21FeDU, also known as
Alloy 825 and UNS N08825, to customer drawing. Contact sales@steelforgepieces.com or
+86 189 2135 9659.

**What certification is supplied?**
EN 10204 3.1 as standard, covering heat number, chemical analysis, heat treatment record,
mechanical results and dimensional report. EN 10204 3.2 witnessed by a third party is available on
request. Ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388.

**How do I get a price?**
Send a drawing or rough dimensions, quantity, governing specification, delivery condition and any
NDT or certification requirement to sales@steelforgepieces.com. Quotations normally go back within
one working day.

## Reference standards

Data on this page is compiled from the standards and producer datasheets listed below. Treat the
figures as guidance. The governing document for any order is the specification named on the
purchase order, and the governing record for any delivered part is its mill test certificate.

- ASTM B564 and ASME SB-564, Nickel Alloy Forgings
- ASTM B425, B424 and B423, UNS N08825 rod and bar, plate sheet and strip, seamless tube
- DIN 17744, Wrought nickel alloys, W.Nr. 2.4858
- EN 10204, Types of inspection documents for metallic products
- EN 10228-3, SEP 1921 and ASTM A388, Ultrasonic testing of forgings
- ASTM G28 and ASTM A262, Intergranular corrosion test methods
- NACE MR0175 and ISO 15156-3, Materials for use in H2S containing environments
- Producer datasheets for Alloy 825 published by Special Metals and VDM Metals

## Related grades

- Incoloy 825 (N08825): https://www.steelforgepieces.com/Nickel-Alloy/Incoloy-825.html
- Incoloy 925: https://www.steelforgepieces.com/Nickel-Alloy/Incoloy-925.html
- Incoloy 945: https://www.steelforgepieces.com/Nickel-Alloy/Incoloy-945.html
- Incoloy 800H: https://www.steelforgepieces.com/Nickel-Alloy/Incoloy-800H.html
- Inconel 625: https://www.steelforgepieces.com/Nickel-Alloy/Inconel-625.html
- Inconel 718: https://www.steelforgepieces.com/Nickel-Alloy/Inconel-718.html
- Hastelloy C-276: https://www.steelforgepieces.com/Nickel-Alloy/Hastelloy-C-276.html
- Monel 400: https://www.steelforgepieces.com/Nickel-Alloy/Monel-400.html
- All nickel alloy grades: https://www.steelforgepieces.com/Nickel-Alloy/

## Citation

Jiangyin Jiangnan Metal Co., Ltd. "NC21FeDU Forgings (Alloy 825 / UNS N08825): grade datasheet and
supply guide." steelforgepieces.com, updated 22 August 2026.
https://www.steelforgepieces.com/Nickel-Alloy/NC21FeDU.html