All designations for 2.4668 — and why there are so many
The same precipitation-hardening nickel superalloy appears under at least ten different designations depending on which standards body, geography, or original trademark applies. Every name in the grid below refers to chemically and mechanically equivalent material.
Engineers sourcing 2.4668 across Europe, North America, Asia, and the Middle East regularly encounter purchase-order mismatches because procurement uses one naming system while the mill certificate uses another. The table below resolves this permanently.
On European mill certificates (EN 10302 / EN 10204), you will see 2.4668 or NiCr19Fe19Nb5Mo3. North American documents use UNS N07718. Aerospace supply chains reference AMS 5663 (double-aged) or AMS 5662 (solution-annealed). All are the same alloy — always request cross-designation confirmation on the Material Test Certificate (EN 10204 3.1 or 3.2) before finalising a purchase order.
Chemical composition of 2.4668 / NiCr19Fe19Nb5Mo3
The composition limits below compare EN 10302 (European standard) and ASTM B637 (North American forging specification). Both specifications are chemically aligned; EN 10302 governs European-certified deliverables.
| Element | EN 10302 Min % | EN 10302 Max % | ASTM B637 Min % | ASTM B637 Max % | Function |
|---|---|---|---|---|---|
| Ni | 50.00 | 55.00 | 50.00 | 55.00 | Matrix / base element |
| Cr | 17.00 | 21.00 | 17.00 | 21.00 | Oxidation & corrosion resistance |
| Nb + Ta | 4.75 | 5.50 | 4.75 | 5.50 | γ'' precipitation hardening |
| Mo | 2.80 | 3.30 | 2.80 | 3.30 | Solid-solution strengthening |
| Fe | — | Balance | — | Balance | Cost dilution (~19 %) |
| Ti | 0.65 | 1.15 | 0.65 | 1.15 | γ' (Ni₃Ti) strengthening |
| Al | 0.20 | 0.80 | 0.20 | 0.80 | γ' (Ni₃Al) & oxidation resistance |
| Co | — | 1.00 | — | 1.00 | Residual / supplemental strength |
| C | — | 0.08 | — | 0.08 | Carbide formers |
| Mn | — | 0.35 | — | 0.35 | Deoxidation |
| Si | — | 0.35 | — | 0.35 | Deoxidation |
| P | — | 0.015 | — | 0.015 | Impurity limit |
| S | — | 0.015 | — | 0.015 | Impurity limit |
| B | — | 0.006 | — | 0.006 | Grain boundary strengthening |
| Cu | — | 0.30 | — | 0.30 | Impurity limit |
| Source: EN 10302:2008 Table 1 and ASTM B637-18. Values in mass percent. Fe is balance; Ni minimum ensured by difference. | |||||
Why 2.4668 is exceptionally strong: the γ'' precipitation mechanism
Most nickel alloys rely on solid-solution strengthening alone. 2.4668 achieves tensile strengths above 1,276 MPa by forming a metastable body-centred tetragonal precipitate called gamma-double-prime (γ''), which is unique to Niobium-bearing nickel alloys.
During the double-aging heat treatment, Niobium atoms (at 4.75–5.50 wt%) diffuse through the face-centred cubic nickel matrix and nucleate as Ni₃Nb particles in the ordered D0₂₂ crystal structure. These coherent precipitates are elastically strained against the matrix, creating a stress field that impedes dislocation movement — the source of the alloy's extraordinary room-temperature strength. The result is the highest yield strength of any commercially produced nickel forging alloy below 650 °C.
A secondary strengthening phase, gamma-prime (γ', Ni₃[Al,Ti]), forms simultaneously. Although γ' contributes less strength than γ'' in 2.4668, it improves grain boundary oxidation resistance and enhances creep life at elevated temperature.
Above approximately 900–1,010 °C, the metastable γ'' transforms irreversibly into the equilibrium orthorhombic phase delta (δ, Ni₃Nb). Delta-phase precipitation at grain boundaries causes severe embrittlement and permanently eliminates the alloy's precipitation hardening response. During forging, any section that cools into this temperature window before reduction is complete risks localised heterogeneous microstructure and cracking. Jiangsu Liangyi controls this risk through continuous infrared temperature monitoring and reheating schedules that keep every billet within the γ'' stability window throughout forging.
The slow aging kinetics of γ'' is what gives 2.4668 its famous post-weld crack resistance. Unlike Waspaloy or Udimet 720, the γ'' phase forms slowly enough that welded assemblies can be air-cooled after welding without triggering strain-age cracking in the heat-affected zone — a critical manufacturing advantage for complex fabrications.
Mechanical and physical properties of 2.4668 forgings
All mechanical values below apply to open die forgings in the double-aged (precipitation-hardened) condition per AMS 5663 / EN 10302 at room temperature unless stated otherwise. Properties vary with section size, forging reduction ratio, and heat treatment variant — verify against your MTC.
| Property | Value | Temperature | Standard reference |
|---|---|---|---|
| Rp0.2 proof strength | ≥ 1,034 MPa | 20 °C (RT) | ASTM B637 |
| Rm tensile strength | ≥ 1,276 MPa | 20 °C (RT) | ASTM B637 |
| Rm tensile strength | ≥ 1,000 MPa | 538 °C (1000 °F) | AMS 5663 |
| Rm tensile strength | ≥ 862 MPa | 649 °C (1200 °F) | AMS 5663 |
| Stress rupture life | ≥ 23 h | 649 °C / 689 MPa | ASTM B637 |
| Young's modulus (E) | 200 GPa | 20 °C (RT) | Typical |
| Young's modulus (E) | 162 GPa | 649 °C | Typical |
| Thermal conductivity | 11.4 W/m·K | 20 °C (RT) | Typical |
| Thermal conductivity | 18.4 W/m·K | 649 °C | Typical |
| CTE (coeff. of thermal expansion) | 13.0 μm/m·°C | 20–300 °C range | EN 10302 |
| CTE (coeff. of thermal expansion) | 14.4 μm/m·°C | 20–650 °C range | EN 10302 |
| Specific heat capacity | 435 J/kg·K | 20 °C (RT) | Typical |
| Electrical resistivity | 1.22 μΩ·m | 20 °C (RT) | Typical |
| Melting range | 1,260–1,336 °C | — | Typical |
| Magnetic permeability | ≤ 1.001 (non-magnetic) | 20 °C (RT) | Typical |
| RT = room temperature (20 °C). "Typical" = published alloy data. "ASTM/AMS" = specification minimum per stated standard. | |||
2.4668 maintains full ductility and impact toughness at temperatures as low as −253 °C (liquid hydrogen temperature). It does not undergo the ductile-to-brittle transition that disqualifies carbon and low-alloy steels from cryogenic service. This makes it the preferred choice for LNG storage vessel flanges, liquid hydrogen pump components, cryogenic valve bodies, and spacecraft propulsion hardware in contact with LH₂ and LOX.
Heat treatment routes for 2.4668 / NiCr19Fe19Nb5Mo3 forgings
The delivered condition determines final properties. Two solution annealing temperatures are used commercially, each producing a different microstructure. Both routes use identical double-aging cycles — only the solution temperature differs, but the downstream property profile changes significantly between the two routes.
Route A — Standard aerospace double-age (AMS 5663 / EN 10302)
Recommended for gas turbines, aerospace engine components, and high-temperature service parts where long-term creep and stress rupture resistance at 600–650 °C are the primary design criteria.
Route B — High-solution double-age (maximum room-temperature strength)
Preferred for downhole drilling tools, cryogenic equipment, and applications where maximum room-temperature tensile strength and toughness are the design-limiting criteria. The higher solution temperature fully dissolves all δ-phase, resulting in a cleaner γ matrix and higher RT tensile properties.
Route A (954–982 °C solution) retains some δ-phase at grain boundaries, which limits grain growth during service and improves long-term creep strength at 600–650 °C. Route B (1,066 °C solution) dissolves all δ-phase, giving slightly higher room-temperature tensile strength but marginally lower creep resistance at elevated service temperature. If you are unsure, send your operating conditions to our technical team — we will recommend the appropriate route at no cost as part of your quotation.
2.4668 forging process and manufacturing capability
2.4668 is one of the most technically demanding nickel alloys to forge, precisely because of the narrow working temperature window between the δ-phase solvus (~1,010 °C) and the forging ceiling (~1,120 °C). Below this window, δ-phase precipitation causes cracking; above it, grain growth destroys mechanical properties.
Jiangsu Liangyi operates a complete in-house production chain for 2.4668 forgings: VIM + ESR melting → ingot homogenisation → open die forging or seamless ring rolling → in-house solution annealing and double-aging → CNC turning / milling → full NDT. Customer-arranged third-party witness inspection by BV, SGS, TÜV, or Intertek is available and can be coordinated upon request. For full product shapes, dimensional ranges, and delivery conditions, see our custom 2.4668 (NiCr19Fe19Nb5Mo3) forged bars, rings, and shafts product page.
| Parameter | Specification / Range | Notes |
|---|---|---|
| Forging temperature | 980–1,120 °C | Billet surface must remain above 980 °C throughout all reduction passes |
| δ-phase danger zone | 900–1,010 °C | Time in this range risks irreversible embrittlement — avoid during all stages |
| Minimum forging ratio | 4:1 (area reduction) | Required to break up as-cast VIM/ESR dendritic structure for ASTM B637 compliance |
| Preheat rate | ≤ 200 °C/h | Prevents thermal gradient cracking in sections ≥ 300 mm |
| Part weight range | 30 kg – 30,000 kg | 6,300-ton hydraulic press for heavy sections |
| Max bar / disc diameter | Up to 2,000 mm | Open die forging capability |
| Max ring OD | Up to 4,000 mm | Seamless rolled ring (SRRM) |
| Melting process | VIM + ESR (standard) | VIM + ESR + VAR triple-melt available upon request for applications requiring maximum material cleanliness |
| Inspection (standard) | UT per ASTM A388, PT per ASTM E165, dimensional | EN 10204 3.1 MTC standard; 3.2 with TPA witness on request |
| Capability data current as of 2025. Specific geometry capability confirmed on request alongside technical quotation. | ||
Applicable standards for 2.4668 / UNS N07718 forgings
Jiangsu Liangyi can supply dual-certified material — for example, EN 10302 + ASTM B637 on the same Material Test Certificate — upon request. State your required standards at the time of inquiry.
| Standard | Issuing body | Scope | Primary market |
|---|---|---|---|
| EN 10302:2008 | CEN (Europe) | Chemical composition and mechanical requirements for Ni and Co alloys for high-temperature service; lists 2.4668 / NiCr19Fe19Nb5Mo3 | European |
| ASTM B637 | ASTM International | Precipitation-hardening Ni alloy bars, forgings, and forging stock — principal North American specification for N07718 forgings | North America / global |
| ASTM B670 | ASTM International | N07718 plate, sheet, and strip | North America |
| AMS 5662 | SAE International | N07718 bars, forgings, rings in solution-annealed condition | Aerospace |
| AMS 5663 | SAE International | N07718 bars, forgings, rings in precipitation-hardened (double-aged) condition — dominant aerospace forging specification | Aerospace |
| AMS 5664 | SAE International | N07718 sheet, strip, plate in solution-annealed + aged condition | Aerospace |
| API 6A / API 17D | API | Chemical composition and mechanical property requirements for wellhead and subsea Christmas tree valve components | Oil & gas |
| NACE MR0175 / ISO 15156 | NACE / ISO | Materials requirements for H₂S sour service oil and gas production equipment — 2.4668 fully qualifies in aged condition | Oil & gas sour service |
| EN 10204 3.1 / 3.2 | CEN (Europe) | Material test certificate types — 3.1 is mill-certified, 3.2 requires independent third-party witness inspection | All industries |
| JIS G 4902 / NCF 718 | JSA (Japan) | Japanese equivalent for bars and forgings in 718-type alloy | Japanese market |
Industrial applications of 2.4668 / NiCr19Fe19Nb5Mo3 forgings
2.4668 accounts for approximately 35–45% of all nickel superalloy tonnage produced globally — by far the most widely deployed high-performance nickel alloy. Its unique combination of very high strength, excellent weldability, and broad corrosion resistance makes it the default first choice across multiple demanding industries.
2.4668 vs related nickel alloys — selection guide for engineers
The choice between 2.4668 and its nearest alternatives comes down to three axes: maximum service temperature, primary failure mode (strength vs. corrosion), and fabrication complexity. Use this table as a first-pass selection tool.
| Property / Criterion | 2.4668 (N07718) | 2.4856 / In.625 (N06625) | 2.4819 / C-276 (N10276) | 2.4669 / X-750 (N07750) |
|---|---|---|---|---|
| Max continuous service °C | 700 °C | 980 °C | 1,038 °C | 980 °C |
| Min tensile strength (RT) | ≥ 1,276 MPa | ≥ 827 MPa | ≥ 760 MPa | ≥ 1,000 MPa |
| Min yield strength (RT) | ≥ 1,034 MPa | ≥ 414 MPa | ≥ 352 MPa | ≥ 690 MPa |
| NACE MR0175 sour service | ✔ Qualifies | ✔ Qualifies | ✔ Qualifies | ✘ Does not qualify |
| Chloride pitting (PREN) | ~35 | ~51 | ~68 | ~28 |
| Post-weld cracking risk | Low (slow γ'' kinetics) | Very low | Very low | Moderate–high |
| Forging difficulty | High (δ-phase risk) | Moderate | Moderate | High |
| Relative material cost | 1.0× (reference) | ~1.1–1.3× | ~1.5–2.0× | ~0.9–1.0× |
| Best primary application | High-strength structural, HPHT O&G, aerospace discs | Corrosion-critical, weld overlay, large forgings | Severe acid / chemical process | High-temp springs, fasteners |
| Cost ratios are indicative and vary with market conditions and order volume. Contact Jiangsu Liangyi for current pricing on your part geometry. | ||||
For a deeper head-to-head between 2.4668 and Inconel 625, see our dedicated page on Inconel 625 / 2.4856 forgings, which includes a forger's-eye view of the practical fabrication differences between the two alloys at heavy section sizes.
Engineer FAQ — 2.4668 / NiCr19Fe19Nb5Mo3
The most common technical questions our engineering team receives from customers worldwide, answered directly and without marketing language.
Need 2.4668 / NiCr19Fe19Nb5Mo3 forgings?
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