X2CrNiMoCuN25-6-3 is a copper-bearing super duplex stainless steel, with a microstructure of roughly equal ferrite and austenite. This datasheet presents the material within the European standard system.
With about 25% chromium, 6% nickel, 3.5% molybdenum, a copper addition and nitrogen, X2CrNiMoCuN25-6-3 reaches a PREN of about 40-42, giving outstanding resistance to chloride pitting, crevice corrosion and stress-corrosion cracking. The copper addition gives improved resistance to reducing acids (sulphuric, hydrochloric). It offers very high mechanical strength with good ductility and toughness, including at sub-zero temperatures.
Typical applications include seawater systems, oil-and-gas subsea and downhole equipment, desalination plant, chemical-process equipment in acid service, and high-strength corrosion-resistant components.
| Property | Value | Unit |
|---|---|---|
| Density | 7.8 | g/cm³ |
| Melting range | 1350-1400 | °C |
| Young's modulus (20 °C) | 200 | GPa |
| Thermal conductivity (20 °C) | 15 | W/m·K |
| Coefficient of thermal expansion (20-100 °C) | 13 | µm/m·°C |
| Specific heat (20 °C) | 480 | J/kg·K |
| Magnetic response | Ferromagnetic (duplex) | — |
| Element | Symbol | Min % | Max % | Role in Alloy |
|---|---|---|---|---|
| Iron | Fe | Balance | — | Base element |
| Chromium | Cr | 24.0 | 26.0 | Ferrite former; corrosion resistance |
| Nickel | Ni | 5.5 | 7.5 | Austenite former; phase balance |
| Molybdenum | Mo | 3.0 | 4.0 | Pitting + crevice resistance |
| Copper | Cu | 1.0 | 2.5 | Reducing-acid resistance |
| Nitrogen | N | 0.20 | 0.30 | Austenite former; strength; pitting |
| Manganese | Mn | — | 1.5 | Deoxidiser |
| Silicon | Si | — | 0.70 | Deoxidiser |
| Carbon | C | — | 0.030 | Low (intergranular resistance) |
| Phosphorus | P | — | 0.035 | Residual impurity |
| Sulphur | S | — | 0.015 | Residual impurity |
Solution-annealed (+AT) condition, per EN 10088-3 for W.Nr. 1.4507.
| Property | Value | Unit |
|---|---|---|
| Tensile strength (Rm) | 730-930 | MPa |
| 0.2% proof strength (Rp0.2) | >=550 | MPa |
| Elongation at fracture | >=25 | % |
| Impact energy (KV, +20 °C) | >=100 | J |
| Brinell hardness | <=270 | HB |
Values per EN 10088-3 (resistant to intergranular corrosion in delivery and welded condition). Confirm against the inspection certificate (EN 10204).
| Environment | Performance | Notes |
|---|---|---|
| Chloride pitting | Outstanding | PREN ~40-42; high CPT |
| Crevice corrosion | Outstanding | High Cr + Mo + N |
| Chloride SCC | Excellent | Duplex structure |
| Reducing acids (H₂SO₄, HCl) | Excellent | Copper addition |
| Seawater | Excellent | Warm chlorinated seawater |
| Intergranular (welded) | Resistant | Low carbon |
The copper addition gives better reducing-acid resistance than copper-free super duplex grades.
Not hardenable by heat treatment; properties are set by solution annealing and phase balance.
Solution Anneal approximately 1080-1120 °C, followed by rapid water quench to retain the balanced ferrite-austenite structure. Rapid cooling is critical owing to the high alloy content. Avoid prolonged exposure in the 300-1000 °C range (sigma-phase / 475 °C embrittlement).
Good weldability by common fusion methods; use a matching or over-alloyed super-duplex filler and control heat input to maintain phase balance.
| Process | Applicability | Filler / Consumable |
|---|---|---|
| GTAW / TIG | Good | Matching super-duplex filler |
| GMAW / MIG | Good | Super-duplex filler |
| SMAW / stick | Good | Matching super-duplex electrode |
No preheat; control interpass temperature and heat input; resistant to intergranular corrosion in the as-welded condition owing to the low carbon.
Machining Guidelines
| Parameter | Recommendation |
|---|---|
| Machinability | Difficult; high strength + work-hardening; rigid setup, carbide tools, low speeds |
| Work hardening | High rate; positive feeds, avoid dwelling |
| Coolant | Ample flood coolant |
Forming Processes
| Process | Notes |
|---|---|
| Hot forming | ~1200-1000 °C; solution anneal + quench afterward |
| Cold forming | Higher forces than standard duplex (very high strength) |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| Marine / seawater | Pumps, valves, seawater systems | Warm chloride resistance |
| Oil & gas | Subsea, downhole equipment | Pitting + sour-service resistance |
| Chemical processing | Acid equipment (H₂SO₄, HCl) | Reducing-acid resistance (Cu) |
| Desalination | Heat exchangers, piping | Hot chloride resistance |
| Product Form | Standard | Notes |
|---|---|---|
| Plate, sheet and strip | EN 10088-2 · W.Nr. 1.4507 | X2CrNiMoCuN25-6-3 |
| Bar, rod, wire and sections | EN 10088-3 · W.Nr. 1.4507 | — |
| Seamless / welded tube | EN 10216-5 / EN 10217-7 · W.Nr. 1.4507 | — |
| Forgings | EN 10222-5 · W.Nr. 1.4507 | — |
| Sour service | ISO 15156-3 | Acid-gas applications |
Copper-bearing 25Cr super duplex stainless steel. W.Nr. 1.4507 (X2CrNiMoCuN25-6-3); EN 10088-3.
| EN Symbol | Cr % | Ni % | Mo % | Cu % | N % | Best Used For |
|---|---|---|---|---|---|---|
| X2CrNiMoCuN25-6-3 | 24-26 | 5.5-7.5 | 3.0-4.0 | 1.0-2.5 | 0.20-0.30 | Cu-bearing super duplex; acids + seawater |
| X2CrNiMoN25-7-4 | 24-26 | 6.0-8.0 | 3.0-4.5 | — | 0.24-0.35 | 2507 super duplex (no Cu) |
| X2CrNiMoCuWN25-7-4 | 24-26 | 6.0-8.0 | 3.0-4.0 | 0.5-1.0 | 0.20-0.30 | Super duplex with W + Cu |
| GX2CrNiMoCuN25-6-3-3 | 24.5-26.5 | 5.5-7.0 | 2.5-3.5 | 2.75-3.5 | 0.12-0.22 | Cast Cu-bearing super duplex |
| X2CrNiMoN22-5-3 | 21-23 | 4.5-6.5 | 2.5-3.5 | — | 0.10-0.22 | Standard duplex |




