N06025 is a high-carbon nickel–chromium–iron alloy with deliberate additions of aluminium (1.8–2.4%) and the reactive elements yttrium and zirconium. The "CA" denotes its defining metallurgy: a self-healing alumina (Al₂O₃) surface layer combined with grain-boundary reinforcement by stable chromium carbides (M₂₃C₆ / M₇C₃). This datasheet presents the material within the American (ASTM / ASME / UNS) standard system.
It is among the most oxidation-resistant and creep-resistant wrought nickel alloys commercially available, with excellent service capability up to 1200 °C (2192 °F) even under cyclic heating and cooling. The tightly adhering alumina scale resists spalling, giving the alloy the lowest mass loss under cyclic oxidation of common high-temperature materials. The high carbon content and carbide precipitation give outstanding high-temperature creep strength.
The alloy is not age-hardened in the conventional sense; it is supplied solution-annealed (typically at 1220 °C to develop a coarse grain size ≥70 µm for maximum creep strength). It offers very good resistance in carburising and oxidising/chlorinating media and good resistance in sulphur-containing oxidising atmospheres. Note: solution-annealed material is sensitive to stress-relaxation cracking between 600–750 °C and should be stabilisation-annealed for long-term service in that range.
Typical values for the solution-annealed condition.
| Property | Value | Unit |
|---|---|---|
| Density (25 °C) | 7.93 | g/cm³ |
| Melting range | 1340–1400 | °C |
| Elastic modulus (20 °C) | 215 | GPa |
| Thermal conductivity (20 °C) | 10.4 | W/m·K |
| Coefficient of thermal expansion (20–100 °C) | 14.15 | µm/m·°C |
| Specific heat capacity (20 °C) | 447 | J/kg·K |
| Electrical resistivity (20 °C) | 1.23 | µΩ·m |
| Magnetic permeability (20 °C) | 1.01 max | Essentially non-magnetic |
| Maximum service temperature (oxidation) | ~1200 | °C |
| Crystal structure | Face-centred cubic (FCC) | — |
Specified per ASTM B166 / B168 (UNS N06025).
| Element | Symbol | Min % | Max % | Role in Alloy |
|---|---|---|---|---|
| Nickel | Ni | Balance | — | Austenitic FCC matrix; high-temperature stability |
| Chromium | Cr | 24.0 | 26.0 | Forms Cr₂O₃ scale; oxidation and corrosion resistance |
| Iron | Fe | 8.0 | 11.0 | Matrix constituent |
| Carbon | C | 0.15 | 0.25 | High carbon; forms M₂₃C₆ / M₇C₃ carbides for creep strength |
| Aluminium | Al | 1.8 | 2.4 | Forms self-healing adherent alumina (Al₂O₃) layer; key oxidation resistance |
| Yttrium | Y | 0.05 | 0.12 | Reactive element; improves oxide scale adhesion |
| Titanium | Ti | — | 0.20 | Microalloying; carbide/nitride former |
| Zirconium | Zr | — | 0.10 | Microalloying; grain-boundary strengthening |
| Manganese | Mn | — | 0.50 | Deoxidiser |
| Silicon | Si | — | 0.50 | Deoxidiser |
| Copper | Cu | — | 0.10 | Residual |
| Phosphorus | P | — | 0.020 | Residual impurity |
| Sulphur | S | — | 0.010 | Residual impurity |
Solution-annealed at 1220 °C (grain size ≥70 µm). Minimum short-term properties per ASTM B166 / manufacturer data.
| Temperature | Yield strength Rp0.2 (min) | Tensile strength Rm (min) | Elongation A (min) |
|---|---|---|---|
| 20 °C | 270 MPa | 675 MPa | 30 % |
| 200 °C | 220 MPa | 625 MPa | 30 % |
| 400 °C | 190 MPa | 580 MPa | 30 % |
| 600 °C | 175 MPa | 520 MPa | 30 % |
| 700 °C | 170 MPa | 420 MPa | 30 % |
ISO V-notch impact toughness (20 °C, solution-annealed, grain size ≥70 µm): transverse >56 J/cm², longitudinal >69 J/cm². Values are minimum specification figures; confirm against the mill test certificate for each delivery.
Typical long-term creep values, solution-annealed (1220 °C).
| Temperature | Creep strength Rm/10⁴ h | Creep strength Rm/10⁵ h |
|---|---|---|
| 650 °C | 215 MPa | 140 MPa |
| 700 °C | 155 MPa | 100 MPa |
| 800 °C | 42 MPa | 20 MPa |
| 900 °C | 18 MPa | 9.7 MPa |
| 1000 °C | 9.0 MPa | 4.5 MPa |
| 1100 °C | 4.4 MPa | 2.1 MPa |
| 1200 °C | 2.2 MPa | 0.8 MPa |
The outstanding creep strength derives from primary M₂₃C₆ / M₇C₃ carbide precipitation, which is the primary reason for selecting this alloy over Alloy 600 / 601 in load-bearing furnace components above 1000 °C.
| Environment | Performance | Notes |
|---|---|---|
| High-temperature oxidation (air) | Outstanding | Adherent Al₂O₃ scale; service to 1200 °C; better than Alloy 601 across the whole range |
| Cyclic oxidation | Outstanding | Lowest mass loss of common high-temperature alloys under cyclic stress |
| Carburisation | Excellent | High Cr + Al; better than Alloy 601 |
| Metal dusting | Very Good | Improved resistance vs Alloy 601 |
| Oxidising sulphur-containing atmospheres | Very Good | Cr + Al provide resistance at elevated temperature |
| Oxidising / chlorinating media | Very Good | Good resistance reported by manufacturer |
| Reducing, low-oxygen atmospheres | Limited | Alumina scale requires oxidising conditions to self-heal |
Supplied in the solution-annealed state. Not a conventional age-hardening alloy; strength derives from carbide precipitation and solution-annealed grain size.
Solution Anneal Temperature: 1220 °C Purpose: Develops coarse grain size (≥70 µm) for maximum creep strength. Retention time scales with section thickness; accelerated cooling (water or compressed air) if further processing follows.
Stabilisation Anneal Temperature: 950 °C, minimum 3 hours Purpose: Required before or after welding, and before long-term (>100 h) service in the 600–750 °C range, to prevent stress-relaxation cracking.
Hot working: 900–1200 °C, followed by rapid cooling; reheat if temperature falls below the lower limit. Post-forming heat treatment recommended.
Weldable by conventional processes (TIG, plasma, GMAW). Owing to lower thermal conductivity and higher thermal expansion than carbon steel, use root gaps of 1–3 mm and included angles of 60–70°. Interpass temperature should not exceed 120 °C; stringer-bead technique recommended.
| Welding Process | Applicability | Filler / Consumable |
|---|---|---|
| GTAW / TIG | Excellent | AWS A5.14 ERNiCrFe-12 |
| Plasma | Excellent | AWS A5.14 ERNiCrFe-12 |
| GMAW / MAG | Good | AWS A5.14 ERNiCrFe-12; multicomponent shielding gas |
Stabilisation anneal at 950 °C may be required before/after welding for service in the 600–750 °C range. Preheating is generally not required.
Machining Guidelines
| Parameter | Recommendation |
|---|---|
| Preferred condition | Solution-annealed |
| Work hardening | Higher than austenitic stainless; keep tool engaged at all times |
| Cutting speed | Low cutting speed, moderate feed; cut below the strain-hardened zone |
| Coolant | Ample water-based emulsion (as for stainless steels) |
Forming Processes
| Process | Notes |
|---|---|
| Hot forming | 900–1200 °C; rapid cool; reheat if below lower limit |
| Cold forming | Higher work hardening than stainless; intermediate/solution anneal if deformation >7% |
| Bending | Inner radius > 3× sheet thickness to avoid damage |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| Thermal processing / heat treatment | Radiant tubes, furnace muffles, rotary and shaft furnaces, kiln rollers, furnace installations | Creep strength + cyclic oxidation resistance to 1200 °C |
| Chemical / petrochemical | Reformers, methanol and ammonia synthesis, hydrogen production | High-temperature strength + carburisation resistance |
| Power / energy | Components for E-fuel syngas cooling, high-temperature ducting | Creep and oxidation resistance |
| Automotive | Exhaust system components, diesel glow plugs | Cyclic oxidation resistance |
| Nuclear / waste | Glass pots for melting radioactive waste | Extreme-temperature stability |
| Product Form | ASTM Standard | ASME Code |
|---|---|---|
| Rod, bar and wire | ASTM B166 | ASME SB-166 |
| Plate, sheet and strip | ASTM B168 | ASME SB-168 |
| Forging stock | ASTM B166 | ASME SB-166 |
| Welding consumable | AWS A5.14 ERNiCrFe-12 | — |
ASME approvals: Section I up to 899 °C (1650 °F); Section VIII Div. 1 up to 982 °C (1800 °F).
| UNS | Ni % | Cr % | Fe % | UTS (annealed) | Max Temp. | Best Used For |
|---|---|---|---|---|---|---|
| N06025 | bal | 24–26 | 8–11 | ≥675 MPa | ~1200 °C | Extreme oxidation + creep; furnace rolls, radiant tubes |
| N06601 | 58–63 | 21–25 | balance | ≥550 MPa | ~1250 °C(ox) | Cyclic oxidation; radiant tubes |
| N06600 | ≥72 | 14–17 | 6–10 | ~655 MPa | ~1095 °C | General high-temp; carburisation/nitriding |
| N06625 | ≥58 | 20–23 | ≤5 | ~830 MPa | ~980 °C | Universal corrosion resistance; seawater |




