Incoloy 825 (UNS N08825 / W. Nr. 2.4858 / NiCr21Mo) is a titanium-stabilized austenitic nickel-iron-chromium alloy with deliberate additions of molybdenum (2.5–3.5 %), copper (1.5–3.0 %), and titanium (0.6–1.2 %). This multi-element chemistry delivers outstanding resistance to both oxidizing and reducing corrosion environments — including sulfuric acid, phosphoric acid, organic acids, seawater, and chloride-bearing media — at temperatures from ambient up to approximately 540 °C.
The key performance advantage of Alloy 825 over conventional austenitic stainless steels (e.g. 316L, 317L) is its high nickel content (38–46 %), which suppresses chloride-induced SCC while the combined molybdenum and copper additions provide exceptional resistance to reducing acids — most notably sulfuric acid at concentrations below 40 % and above 90 %, and phosphoric acid across the full concentration range. Titanium stabilization prevents sensitization and intergranular attack in the heat-affected zone after welding, making the alloy particularly suitable for fabricated vessels and piping assemblies used in sour gas processing and offshore facilities. The alloy’s stable austenitic structure also maintains toughness down to cryogenic temperatures, an advantage in offshore LNG applications.
SHUNFU METAL produces N08825 bar via double-melting (VIM + ESR) for critical sour-service grades. Bars are stabilize-annealed at 940–980 °C, water-quenched, then subject to 100 % ultrasonic testing per ASTM E114. IGC testing per ASTM A262 Practice B or C is available upon request. Hardness is capped at 35 HRC / 331 HBW for NACE MR0175 compliance. Chemical composition and mechanical properties are verified by third-party inspection bodies (SGS, Bureau Veritas, TÜV, Lloyd’s) as required.
In oil and gas service, Incoloy 825 bar is specified wherever sour (H₂S) environments, high chloride concentrations, or acidic process fluids would rapidly attack austenitic stainless steels. The alloy is listed in NACE MR0175 / ISO 15156 for sour service and approved under ASME Section VIII pressure vessel codes up to 538 °C. SHUNFU METAL supplies N08825 bar from VIM-cast heats, stabilize-annealed at 940–980 °C, ultrasonically tested per ASTM E114, and accompanied by EN 10204 3.1 / 3.2 MTR on every shipment.
Equivalent Grades & Applicable Standards
| Standard Body | Designation | Applicable Specification / Form |
|---|---|---|
| ASTM / ASME | UNS N08825 | B425 / SB-425 (bar & shapes), B423 (pipe & tube), B424 (plate/sheet/strip), B163 (heat exchanger tube), B564 / SB-564 (forgings) |
| EN / DIN | 2.4858 / NiCr21Mo | EN 10028-7 (pressure vessels), DIN 17744 (bar), EN ISO 9723 (bar & wire) |
| BS | NA 16 | BS 3076 (bar & billet) |
| AFNOR (France) | NC 21 FeDU | NF A36-209 |
| JIS | NCF 825 | JIS G4901 (bar), JIS G4902 (plate), JIS G4903 (pipe & tube) |
| GB (China) | NS142 / GHM32 | GB/T 15007 (wrought nickel alloy designation) |
| ISO | NW 8825 | ISO 9723 (bar), ISO 9724 (wire) |
Oil & Gas Applications — N08825 Bar Components
Downhole & Wellbore
- Tubing hangers & completion strings
- Downhole valve bodies (sour gas wells)
- Packer mandrels & seal bores
- Downhole pump shafts
- Wire-line tool housings
Wellhead & Christmas Tree
- Wellhead valve stems & bodies
- Gate valve seats & trim components
- Choke body inlets (sour service)
- Casing head flanges
- Subsea connector studs & bolts
Offshore & Subsea
- Subsea manifold components
- Riser clamp bodies
- Seawater pump shafts & impellers
- Mooring chain guide rollers
- Flexible joint inner core bars
Refinery & Gas Processing
- HDS reactor internals & distributor bars
- Amine gas-treating vessel internals
- Sour-water stripper components
- H₂S scrubber shaft & agitator bars
- Phosphoric acid evaporator internals
Pipelines & Transport
- Sour gas pipeline pig-launcher bars
- Corrosion-resistant valve bodies
- Pipeline isolation joint components
- Expansion bellows tie rods
- Metering skid manifold bars
Flue Gas & Environmental
- FGD absorber agitator shafts
- Stack gas scrubber internals
- Electrostatic precipitator electrodes
- Offshore flare tip supports
- Acid dew-point corrosion-resistant parts
Supply — Bar Sizes & Forms (Incoloy 825 / N08825)
| Form | Size Range | Standard / Process | Length |
|---|---|---|---|
| Hot-Rolled Round Bar | Ø 8 – Ø 200 mm | ASTM B425 / EN ISO 9723 | 2,000 – 6,000 mm |
| Cold-Drawn Round Bar | Ø 6 – Ø 80 mm | ASTM B425 (cold-drawn) | 1,000 – 4,000 mm |
| Hot-Rolled Flat Bar | T 6–120 × W 20–400 mm | ASTM B425 / EN ISO 9724 | 2,000 – 6,000 mm |
| Forged Round Bar | Ø 80 – Ø 900 mm | ASTM B564 / EN 10243 | 500 – 3,500 mm |
| Forged Flat Bar / Slab | T 30–300 × W 50–800 mm | ASTM B564 / EN 10243 | 500 – 3,000 mm |
| Hexagonal / Square Bar | Across-flat 8 – 100 mm | ASTM B425 | 1,000 – 4,000 mm |
All stock is stabilize-annealed (940–980 °C / WQ). Surface: black (as-forged/rolled), turned, or centreless-ground. Tolerances per ASTM B425 or customer specification. NACE MR0175 hardness compliance (≤ 35 HRC / 331 HBW) certified on request. Non-standard dimensions available with 2–4-week lead time from SHUNFU METAL’s dedicated nickel-alloy forge and rolling lines.
Chemical Composition — Incoloy 825 / N08825 (ASTM B425)
| Element | Min (%) | Max (%) |
|---|---|---|
| Ni | 38.0 | 46.0 |
| Cr | 19.5 | 23.5 |
| Fe | 22.0 | bal. |
| Mo | 2.5 | 3.5 |
| Cu | 1.5 | 3.0 |
| Ti | 0.6 | 1.2 |
| Al | — | 0.20 |
| C | — | 0.05 |
| Mn | — | 1.0 |
| Si | — | 0.5 |
| S | — | 0.03 |
Source: ASTM B425-19. Titanium content (0.6–1.2 %) provides carbide stabilization, preventing sensitization during welding. Molybdenum + copper synergy ensures resistance to both reducing (H₂SO₄, HCl) and oxidizing (HNO₃) acids. SHUNFU METAL performs OES + IGF analysis on every heat, with full chemistry traceable to heat number.
Mechanical Properties — Incoloy 825 Bar (ASTM B425)
| Form / Condition | UTS (MPa) | 0.2% YS (MPa) | Elongation (%) | Hardness |
|---|---|---|---|---|
| Bar / Annealed (min. per ASTM B425) | 590 min. | 240 min. | 30 min. | ≤ 35 HRC |
| Bar / Annealed (typical) | 690 | 325 | 45 | ~138 HV |
| Plate / Annealed (typical) | 660 | 340 | 45 | ~135 HV |
| Tube / Annealed (typical) | 770 | 440 | 35 | ~160 HV |
| Tube / Cold-Drawn (typical) | 1,000 | 880 | 15 | ~280 HV |
| Sheet / Annealed (typical) | 760 | 420 | 39 | ~155 HV |
Heat treatment: stabilize anneal at 940–980 °C, water quench or rapid air cool. For NACE MR0175 / ISO 15156 sour-service compliance, hardness must not exceed 35 HRC (331 HBW / 355 HV). SHUNFU METAL performs tensile testing per ASTM E8, Brinell / Vickers hardness per ASTM E10 / E92, and IGC screening per ASTM A262 Practice B or C on all sour-service orders. Impact testing per ASTM E23 Charpy V-notch available for low-temperature and subsea applications.
Need Incoloy 825 / N08825 to the specification above?
Send the size, condition, quantity and any NACE or PMI requirements — we reply with mill availability, lead time and a priced offer, usually within one working day.