UNS N08825 Alloy Incoloy 825 Tubing Seamless For Oil And Gas
UNS N08825 is a nickel-iron-chromium alloy with significant additions of molybdenum, copper, and titanium. This austenitic nickel-iron-chromium alloy is specifically designed to provide exceptional resistance to both reducing and oxidizing acids, as well as stress-corrosion cracking and pitting in chloride-containing environments.
What sets UNS N08825 apart is its stabilized structure – the addition of titanium prevents intergranular corrosion after welding, making it suitable for fabricated equipment without post-weld heat treatment. The alloy also contains copper, which provides outstanding resistance to sulfuric and phosphoric acids. UNS N08825 maintains excellent mechanical properties from cryogenic temperatures up to 540°C (1000°F).
| Parameter | Details |
|---|---|
| Standard | ASTM B423 (Seamless Tube), ASTM B163 (Heat Exchanger Tube), ASTM B424 (Plate/Sheet), ASME SB423 |
| Grade / UNS | Incoloy 825 / UNS N08825 / W.Nr. 2.4858 |
| Type | Seamless tube / Welded tube (ERW / EFW) |
| Outer Diameter | 6.0 mm – 610 mm (1/8″ – 24″) |
| Wall Thickness | 0.5 mm – 50 mm (SCH 5S – XXS) |
| Length | 6 m / 9 m / 12 m, or random lengths |
| Process | Cold drawn / Cold rolled (seamless); Plate rolled (welded) |
| Finish | Annealed & pickled / Bright annealed |
| Ends | Plain end / Beveled end / Threaded |
| Packaging | Hexagonal bundles + plastic end caps + seaworthy wooden crates or pallets |
The chemical composition of UNS N08825 complies with ASTM B425, B424, and B423 standards.
| Element | Content (%) | Role |
|---|---|---|
| Nickel (Ni) | 38.0 – 46.0 | Provides SCC resistance and austenitic stability |
| Iron (Fe) | ≥ 22.0 (balance) | Base element |
| Chromium (Cr) | 19.5 – 23.5 | Enhances oxidation and corrosion resistance |
| Molybdenum (Mo) | 2.5 – 3.5 | Improves pitting and crevice corrosion resistance |
| Copper (Cu) | 1.5 – 3.0 | Provides resistance to reducing acids (sulfuric/phosphoric) |
| Titanium (Ti) | 0.6 – 1.2 | Stabilizes against intergranular attack |
| Carbon (C) | ≤ 0.05 | Minimized to prevent sensitization |
| Manganese (Mn) | ≤ 1.00 | Aids in hot workability |
| Silicon (Si) | ≤ 0.50 | Improves oxidation resistance |
| Aluminum (Al) | ≤ 0.20 | Deoxidizer |
| Sulfur (S) | ≤ 0.03 | Controlled for hot workability |
| Phosphorus (P) | ≤ 0.03 | Minimized to maintain ductility |
Room Temperature Properties (Annealed Condition)
| Property | Metric (MPa) | Imperial (ksi) |
|---|---|---|
| Tensile Strength (Rm) | ≥ 586 | ≥ 85 |
| Yield Strength 0.2% Proof (Rp0.2) | ≥ 241 | ≥ 35 |
| Elongation (A) | ≥ 30% | ≥ 30% |
| Density | 8.14 g/cm³ | 0.294 lb/in³ |
| Melting Point | 1370 – 1400°C | 2500 – 2550°F |
| Modulus of Elasticity | 196 GPa | 28.4 x 10³ ksi |
| Environment | Performance |
|---|---|
| Sulfuric acid (H₂SO₄) | Excellent – up to 40% concentration at boiling |
| Phosphoric acid (H₃PO₄) | Excellent – industry standard for fertilizer production |
| Nitric acid (HNO₃) | Good to excellent |
| Hydrochloric acid (HCl) | Good in dilute concentrations (<10%) |
| Organic acids | Excellent (acetic, formic, citric) |
| Chlorides (NaCl) | Good pitting resistance; excellent SCC resistance |
| Seawater | Moderate – good for many applications |
| Caustic solutions | Good |
UNS N08825 offers good weldability with important advantages:
| Property | Detail |
|---|---|
| Post-weld heat treatment | Not required for corrosion resistance (titanium stabilized) |
| Sensitization risk | Very low – titanium prevents carbide precipitation |
| Recommended methods | TIG, MIG, SMAW, SAW |
| Filler metal | Matching UNS N08825 filler (ERNiCrMo-3 or ENiCrMo-3) |
| Preheating | Generally not required |
| Interpass temperature | Maintain below 150°C (300°F) |
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