NiCr22Mo9Nb is a nickel–chromium–molybdenum alloy with niobium additions, used for its high strength, excellent fabricability (including joining), and outstanding corrosion resistance. Service temperatures range from cryogenic to 982 °C (1800 °F). This datasheet presents the material within the European (DIN / EN / Werkstoff-Nummer / VdTÜV) standard system.
Its strength derives from the stiffening effect of molybdenum and niobium on the nickel–chromium matrix, so precipitation-hardening treatments are not required. This same combination of elements gives superior resistance to a wide range of severe corrosive environments, as well as to high-temperature oxidation and carburisation. The high molybdenum content makes the alloy very resistant to pitting and crevice corrosion, while niobium stabilises it against sensitisation during welding; the high nickel content provides freedom from chloride-ion stress-corrosion cracking.
These properties make the alloy an excellent choice for sea-water and chemical-processing applications, aerospace ducting and engine-exhaust systems, and nuclear reactor-core and control-rod components. It offers freedom from local attack, high corrosion-fatigue strength, high tensile strength, and excellent weldability and brazeability across its full service range.
Typical values per Special Metals official datasheet, annealed condition.
| Property | Value | Unit |
|---|---|---|
| Density | 8.44 | g/cm³ |
| Melting range | 1290–1350 | °C |
| Elastic modulus (21 °C, annealed) | 207.5 | GPa |
| Shear modulus (21 °C, annealed) | 81.4 | GPa |
| Poisson's ratio (21 °C) | 0.278 | — |
| Specific heat capacity (21 °C) | 410 | J/kg·K |
| Electrical resistivity (21 °C) | 1.29 | µΩ·m |
| Thermal conductivity (21 °C) | 9.8 | W/m·K |
| Coefficient of thermal expansion (21–93 °C) | 12.8 | µm/m·°C |
| Magnetic permeability (200 Oe) | 1.0006 | Essentially non-magnetic |
| Curie temperature | <–196 | °C |
| Maximum service temperature | ~982 | °C |
Composition per EN 10095 (W.Nr. 2.4856, NiCr22Mo9Nb).
| Element | Symbol | Min % | Max % | Role in Alloy |
|---|---|---|---|---|
| Nickel | Ni | 58.0 | balance | Austenitic FCC matrix; chloride SCC resistance |
| Chromium | Cr | 20.0 | 23.0 | Oxidation / corrosion resistance |
| Molybdenum | Mo | 8.0 | 10.0 | Solid-solution strengthening; pitting resistance |
| Niobium (+ Ta) | Nb | 3.15 | 4.15 | Stabiliser; matrix strengthening |
| Iron | Fe | — | 5.0 | Residual |
| Cobalt | Co | — | 1.0 | Residual |
| Carbon | C | 0.03 | 0.10 | Carbide formation |
| Manganese | Mn | — | 0.5 | Deoxidiser |
| Silicon | Si | — | 0.5 | Deoxidiser |
| Titanium | Ti | — | 0.4 | Residual |
| Aluminium | Al | — | 0.4 | Residual |
| Copper | Cu | — | 0.5 | Residual |
| Phosphorus | P | — | 0.02 | Residual impurity |
| Sulphur | S | — | 0.015 | Residual impurity |
Nominal: Ni-22Cr-9Mo-3.6(Nb+Ta). Per EN 10095, Nb+Ta = 3.15-4.15%. Molybdenum and niobium give solid-solution strengthening and corrosion resistance. Maximum application temperature in air ~1000 °C.
Annealed (+A) condition, per EN 10095 for W.Nr. 2.4856.
| Property | Value | Unit |
|---|---|---|
| Tensile strength (Rm) | 760–1050 | MPa |
| 0.2% proof strength (Rp0.2) | 380–415 | MPa |
| Elongation at fracture (A) | 25–30 | % |
| Brinell hardness | ≤240 | HB |
Values per EN 10095. Confirm against the inspection certificate (EN 10204).
| Environment | Performance | Notes |
|---|---|---|
| Sea water | Outstanding | Freedom from pitting and crevice attack; high corrosion-fatigue strength |
| Chloride stress-corrosion cracking | Outstanding | High Ni content gives immunity |
| Pitting and crevice corrosion | Outstanding | High Mo content |
| Oxidising acids | Excellent | Ni + Cr resist oxidising chemicals |
| Non-oxidising / reducing acids | Excellent | High Ni + Mo content |
| Mixed acids (e.g. HCl + HNO₃) | Excellent | Resists directly opposite corrosion types |
| High-temperature oxidation | Good | Protective oxide retained; scaling significant above ~982 °C |
| Carburisation | Good | Resists high-temperature carburisation |
| Weld sensitisation | Excellent | Nb stabilises against intergranular attack |
The alloy is matrix-stiffened, not precipitation-hardened; heat treatment is for annealing, stress relief, and solution treatment only.
Anneal Temperature: 927–1038 °C (1700–1900 °F), time commensurate with thickness Purpose: Softening and recrystallisation; recommended for service at 650 °C and below, and for fatigue/tensile-critical applications.
Solution Treatment Temperature: 1093–1204 °C (2000–2200 °F) Purpose: Optimum creep-rupture resistance for service above 650 °C.
Stress Relief Heating cold-drawn material at 595–760 °C reduces residual stress; virtually complete at 871 °C. Cooling rate has no significant effect on properties.
Readily joined by conventional welding processes. Matching filler metals are highly resistant to corrosion and oxidation and require no post-weld heat treatment to maintain strength and ductility from cryogenic to 982 °C. Niobium stabilisation prevents weld-zone sensitisation.
| Welding Process | Applicability | Filler / Consumable |
|---|---|---|
| GTAW / TIG | Excellent | DIN EN ISO 18274 S Ni 6625 (NiCr22Mo9Nb) |
| GMAW / MIG | Excellent | DIN EN ISO 18274 S Ni 6625 (NiCr22Mo9Nb) |
| SMAW / stick | Excellent | DIN EN ISO 14172 E Ni 6625 |
The filler metals are also used as "overmatching" products for joining 316/317 stainless, 6 % Mo super-austenitic stainless, and other Ni-Cr-Mo alloys.
Machining Guidelines
| Tooling | Surface Speed | Feed |
|---|---|---|
| High-speed steel | 4.0–10.7 m/min | 0.13–0.51 mm/rev |
| Coated carbide | 14–34 m/min | 0.13–0.51 mm/rev |
Forming Processes
| Process | Notes |
|---|---|
| Hot forming | Heat to (not above) 1175 °C; heavy forging 1175→1010 °C; light reductions down to 925 °C; 15–20 % minimum reductions |
| Cold forming | Standard processes; high work-hardening rate; tensile >2000 MPa achievable in fine wire after 75–90 % reduction |
| Annealing between operations | 927–1038 °C |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| Marine | Mooring cables, propeller blades, exhaust ducts, undersea cable sheathing, submarine fittings | Sea-water pitting/crevice resistance; chloride SCC immunity |
| Aerospace | Ducting, engine-exhaust and thrust-reverser systems, honeycomb structures, bellows, turbine shroud rings | High strength + oxidation + thermal-fatigue resistance |
| Chemical processing | Reaction vessels, distillation columns, heat exchangers, transfer piping, valves, bubble caps | Broad-spectrum corrosion resistance |
| Nuclear | Reactor-core and control-rod components | Strength + pitting/SCC resistance in 260–316 °C water |
| Power generation | High-temperature tubing, bellows, seals | Allowable design strength at 649–760 °C |
| Product Form | EN / DIN Standard | VdTÜV | ISO |
|---|---|---|---|
| Rod and bar | EN 10095 · DIN 17752 | VdTÜV 499 | ISO 9723 |
| Forgings | DIN 17754 | — | ISO 9725 |
| Wire | DIN 17753 | — | ISO 9724 |
| Plate, sheet and strip | EN 10095 · DIN 17750 | VdTÜV 499 | ISO 6208 |
| Seamless tube | DIN 17751 | VdTÜV 499 | ISO 6207 |
| Composition (all forms) | DIN 17744 | — | ISO 4955A |
| Welding consumables | DIN EN ISO 18274 S Ni 6625 · EN ISO 14172 E Ni 6625 | — | — |
VdTÜV material data sheet 499 covers rod, bar, plate, sheet, strip and tube; BS 3072–3076 NA21; listed in ISO 15156-3.
| EN Symbol | Ni % | Cr % | Mo % | UTS (annealed) | Max Temp. | Best Used For |
|---|---|---|---|---|---|---|
| NiCr22Mo9Nb | ≥58 | 20–23 | 8–10 | 827–1034 MPa | ~982 °C | Sea-water; chemical processing; universal corrosion |
| NiCr15Fe | ≥72 | 14–17 | — | ~655 MPa | ~1095 °C | General high-temp; carburisation/nitriding |
| NiCr23Fe | 58–63 | 21–25 | — | ~550 MPa | ~1250 °C(ox) | Cyclic oxidation; radiant tubes |
| NiCr23Co12Mo | 44.5 | 20–24 | 8–10 | ~734 MPa | ~1100 °C | Gas-turbine hot section; creep strength |
| NiCr19Fe19Nb5Mo3 | 50–55 | 17–21 | 2.8–3.3 | ~1240 MPa(aged) | ~650 °C | High-strength age-hardenable structures |
| NiCr21Mo | 38–46 | 19.5–23.5 | 2.5–3.5 | ~690 MPa | ~540 °C | Acid resistance; Fe-Ni-Cr-Mo economy grade |




