2.4654 stands apart from the broader nickel superalloy family because of a dual-mechanism strengthening system that operates effectively well above 700°C — the threshold where most structural metals begin to fail. A solid-solution matrix of Ni-Cr-Co-Mo is reinforced by coherent γ′ (gamma prime) precipitates of Ni₃(Al,Ti), combining oxidation immunity with creep rupture strength that has made this alloy indispensable in rotating power machinery for more than four decades.
Naming & Cross-Reference: 2.4654, NC20K14, NiCr20Co13Mo4Ti3Al
The same alloy carries at least three distinct designations across national standard systems — a frequent source of procurement confusion for engineering teams working internationally. All three names refer to the same material governed by the same composition limits when specified under EN 10302.
Werkstoff-Nr. under EN 10302. Dominant designation in European industrial procurement, pressure equipment directives, and turbine OEM documentation.
"NC" = nickel-chromium base. "20" = nominal 20% Cr. "K" = cobalt (AFNOR code). "14" = ~14% Co. Widely cited in French nuclear and EDF power generation specifications.
Fully descriptive chemical name. Unambiguous across all national systems. Used on material test certificates and in international technical literature.
Closely related to Nimonic 105 / Udimet 630 in the Ni-Cr-Co-Mo-Ti-Al family. Always confirm exact composition against EN 10302 limits when substituting.
When reviewing material test certificates, confirm which normative document is invoked. A certificate citing NC20K14 under a French AFNOR reference and one citing 2.4654 under EN 10302 describe the same composition limits — but always cross-check the chemical analysis table directly rather than relying on the designation string alone.
Chemical Composition (EN 10302 Limits)
The alloy's performance is encoded in precise elemental balance. Each addition serves a specific metallurgical function; the combined Ti + Al content (4.3–5.3% total) is the primary driver of γ′ volume fraction and, therefore, high-temperature strength.
| Element | Symbol | Min (%) | Max (%) | Typical (%) | Metallurgical Role |
|---|---|---|---|---|---|
| Nickel | Ni | Bal. | Bal. | ~53–57 | FCC matrix host; corrosion-resistant base; γ′ host lattice |
| Chromium | Cr | 18.0 | 22.0 | ~20.0 | Oxidation & hot-corrosion resistance via stable Cr₂O₃ surface scale |
| Cobalt | Co | 11.0 | 15.0 | ~13.0 | Solid-solution hardening; raises γ′ solvus temperature, extending service range |
| Molybdenum | Mo | 3.5 | 5.0 | ~4.0 | Solid-solution strengthening; reduces stacking-fault energy, inhibits dislocation climb |
| Titanium | Ti | 2.5 | 3.5 | ~3.0 | Primary γ′ [Ni₃(Al,Ti)] former; largest single contributor to precipitate volume fraction |
| Aluminium | Al | 0.8 | 1.8 | ~1.3 | γ′ former; alumina scale formation; enhances oxidation resistance at peak temperatures |
| Carbon | C | — | 0.10 | ~0.06 | Grain boundary carbides (M₂₃C₆, MC); resists boundary sliding under creep load |
| Iron | Fe | — | 5.0 | ~1.5 | Residual; limited to prevent topologically close-packed (TCP) phase formation |
| Silicon | Si | — | 1.0 | — | Deoxidiser in melting; limited to avoid embrittlement in service |
| Manganese | Mn | — | 1.0 | — | Deoxidiser; minimal in production heats |
| Boron | B | — | 0.008 | — | Grain boundary cohesion; improves creep ductility and rupture elongation |
| Zirconium | Zr | — | 0.15 | — | Grain boundary strengthening; reduces oxide penetration |
The compositional name NiCr20Co13Mo4Ti3Al encodes the four primary additions beyond the nickel base: ~20% Cr, ~13% Co, ~4% Mo, ~3% Ti, with implied aluminium — a compact chemical fingerprint that identifies the alloy without reference to any national numbering system and is directly readable on a spectrometric test certificate.
Strengthening Mechanism: Dual-Phase γ / γ′ Architecture
The key differentiator of 2.4654 is a dual-mechanism strengthening system that operates simultaneously at the matrix level and at the precipitate level, remaining effective well above the temperature range where most precipitation-hardened steels overage and lose strength.
Microstructure Schematic: 2.4654 after full age treatment
Particle size: 50–200 nm in optimally forged and heat-treated product. Bimodal γ′ distribution is the target of the three-stage heat treatment sequence.
The γ (Gamma) Matrix — Solid-Solution Strengthening
The continuous phase is a face-centred cubic (FCC) solid solution of nickel, chromium, cobalt, and molybdenum. Chromium provides the primary oxidation and hot-corrosion barrier through formation of a stable, adherent Cr₂O₃ surface scale. Cobalt partitions into the matrix, raising the γ′ solvus temperature and extending the alloy's effective service range upward. Molybdenum reduces stacking-fault energy, which suppresses dislocation climb and cross-slip at elevated temperature — an independent strengthening contribution that operates regardless of γ′ content.
The γ′ (Gamma Prime) Phase — Precipitation Strengthening
Dispersed coherently within the matrix are ordered Ni₃(Al,Ti) intermetallic particles — the γ′ phase. Unlike most hardening precipitates in engineering alloys, γ′ in the Ni-base system exhibits an anomalous yield stress increase with rising temperature up to approximately 750–850°C. This means the alloy resists dislocation motion more effectively as it heats up — until γ′ particles begin dissolving near the solvus. This anomalous behaviour is unique to the L1₂ crystal structure of the γ′ phase and is the primary reason nickel superalloys outperform iron-based alloys at elevated temperatures.
Volume fraction (~35–45%) — controlled by Al + Ti content; higher fractions increase strength but reduce ductility and forgeability. Particle size (50–200 nm) — controlled by aging temperature and time; coarsening via Ostwald ripening at service temperature governs long-term creep life. Morphology — cuboidal γ′ particles aligned in the [100] direction provide optimal resistance to dislocation cutting (for small particles) and Orowan bypass (for larger particles).
Grain Boundary Carbides
Carbon (~0.06% typical) precipitates as M₂₃C₆ and MC-type carbides preferentially at grain boundaries during heat treatment. A discontinuous, blocky distribution pins boundaries against sliding under sustained creep load, improving rupture ductility. Continuous carbide films are detrimental — they create crack initiation sites. The carbon specification window in 2.4654 (max 0.10%) and the aging temperatures are calibrated to achieve the desired morphology without crossing into the embrittling regime.
Mechanical & Physical Properties
The following data is representative of solution-annealed and double age-hardened wrought / forged 2.4654. Properties of cast product differ substantially and must not be substituted in forging specification documents.
Room-Temperature Mechanical Properties (Forged, Aged per EN 10302)
Elevated-Temperature Tensile Strength (Forged Bar, Full Aged)
| Test Temperature | UTS (MPa) | Rp0.2 (MPa) | Elongation (%) |
|---|---|---|---|
| 20°C (RT) | ≥ 850 | ≥ 620 | ≥ 18 |
| 400°C | ~780 | ~600 | ≥ 16 |
| 600°C | ~740 | ~570 | ≥ 14 |
| 750°C | ~680 | ~520 | ≥ 12 |
| 850°C | ~480 | ~360 | ≥ 10 |
| 950°C | ~240 | ~180 | ≥ 20 (ductile) |
Creep Rupture Strength (Typical Forged Product)
| Temperature | 100 h Rupture Stress | 1,000 h Rupture Stress | Typical Application |
|---|---|---|---|
| 700°C | ~490 MPa | ~400 MPa | Steam turbine discs, fasteners |
| 800°C | ~280 MPa | ~200 MPa | Gas turbine rings, valve spindles |
| 850°C | ~180 MPa | ~120 MPa | High-temp casings, bolt blanks |
| 900°C | ~100 MPa | ~60 MPa | Labyrinth seal rings (static load) |
Physical Properties
| Property | Value | Condition / Notes |
|---|---|---|
| Melting range | 1310–1355°C | Solidus to liquidus |
| Thermal conductivity | ~10.5 W/(m·K) | At 20°C |
| Mean CTE (20–750°C) | ~12.9 × 10⁻⁶ K⁻¹ | Design value for thermal stress calculation |
| Specific heat capacity | ~450 J/(kg·K) | Room temperature |
| Electrical resistivity | ~1.20 µΩ·m | Room temperature |
These property values apply to wrought, fully heat-treated forged product. If you are sourcing components that must meet these minimums, our 2.4654 forged rings, discs, and bars are produced and tested to EN 10302 with full 3.1 MTC documentation.
Heat Treatment: Solution Anneal & Age-Hardening
The as-forged microstructure is not the final state. Alloy 2.4654 reaches its specified mechanical properties only after a three-stage heat treatment sequence. Deviations in temperature (±10°C or more), hold time, or cooling rate directly alter the γ′ size distribution and compromise creep life or tensile strength in the finished component.
Solution Annealing (Solutionising)
Heat the forging above the γ′ solvus to dissolve all precipitate phases and homogenise the alloy matrix. Establishes the starting grain size for subsequent aging and erases heterogeneous precipitation introduced during the forging thermal cycle. Rapid cooling is essential to suppress early γ′ precipitation on the way down.
Primary Aging (Stabilisation)
First aging step develops coarse γ′ particles (primary population) that contribute principally to creep rupture resistance and long-term thermal stability. Grain boundary M₂₃C₆ carbides also precipitate in the desired discontinuous, blocky morphology during this stage.
Secondary Aging (Precipitation Hardening)
Final step grows a fine secondary γ′ population filling the matrix between coarser primary precipitates. This bimodal γ′ distribution — coarse particles for creep resistance, fine particles for tensile and fatigue strength — is the intended final microstructural state and cannot be achieved by single-temperature aging.
Heat treatment must always be performed on the finished forging geometry, not on bar stock prior to forging. The forging thermal cycle and deformation history both influence precipitation kinetics and must be accounted for in the heat treatment sequence. At Jiangsu Liangyi, all 2.4654 forgings are heat-treated in calibrated furnaces with ±10°C uniformity; thermocouple records and furnace charts are supplied as part of the EN 10204 Type 3.1 material test certificate.
Applicable Standards and Certifications
Procurement of 2.4654 forgings for safety-critical applications requires explicit alignment on which normative documents govern the purchase order. The table below lists the most commonly invoked standards across power generation, nuclear, and oil & gas supply chains.
| Standard | Scope | Relevance to 2.4654 Forgings |
|---|---|---|
| EN 10302:2008 | Heat-resistant steels and nickel alloys — technical delivery conditions | Primary European specification; defines chemical limits, mechanical property minimums, and testing requirements for wrought product |
| DIN 17742 | Nickel wrought alloys — properties | Historical DIN predecessor; still cited in older German turbine and pressure vessel documentation alongside EN 10302 |
| EN 10204 | Metallic products — types of inspection documents | Type 3.1 MTC required for most turbine and pressure applications; Type 3.2 for nuclear and aerospace OEM-qualified supply chains |
| EN 10228-4 | Non-destructive testing of steel forgings — ultrasonic testing | UT acceptance class for open-die forgings and seamless rolled rings; class typically specified by OEM on drawing |
| ASTM E112 | Standard test methods for average grain size | ASTM No. 5 or finer typically required; confirmed by optical metallography on representative test piece |
| PED 2014/68/EU | Pressure Equipment Directive | Applicable standard for pressure-retaining equipment sold in the EU — customer responsibility to confirm their equipment assembly meets PED; Jiangsu Liangyi supplies forgings with full MTCs to support customer PED compliance |
| RCC-M / ASME III | Nuclear mechanical equipment codes (French / US) | Governing codes for nuclear pressure boundary components — Jiangsu Liangyi can supply forgings with chemistry and mechanical properties meeting RCC-M / ASME III material requirements; customer or their notified body holds code authority |
| ISO 9001:2015 | Quality management systems — requirements | Jiangsu Liangyi Co., Limited holds ISO 9001:2015 certification. Required by most OEM Tier-1 qualification programmes for turbine and industrial supply chains. |
Jiangsu Liangyi supplies 2.4654 / NC20K14 forged components with EN 10204 Type 3.1 inspection certificates as standard, covering spectrometric chemical analysis, mechanical testing, hardness, and ultrasonic examination results — all from a single traceable heat and forging lot.
Industrial Applications & Forged Product Forms
The combination of long-term creep resistance, oxidation immunity up to ~1050°C, and fatigue strength under cyclic thermal loading makes 2.4654 the material of choice across four primary industries where component failure carries significant safety and economic consequences.
Power Generation — Steam & Gas Turbines
Turbine disc forgings, blade root blanks, valve spindles, bolting bar stock, labyrinth seal rings, and bearing housing components where operating temperatures exceed 600°C for service lives measured in decades.
Nuclear Energy
Pressure-retaining components and structural forgings in primary circuit environments where long-term dimensional stability under sustained load and elevated temperature is mandatory. Forgings supplied with chemistry and properties meeting RCC-M / ASME III material clauses; end-equipment qualification by customer or notified body.
Oil & Gas — Upstream & Midstream
Wellhead valve components, compressor rings, and downhole equipment where H₂S corrosion resistance, NACE MR0175 compliance, and mechanical strength beyond standard austenitic grades are simultaneously required.
Industrial Processing
Petrochemical reformer components, heat-exchanger tube sheets, furnace fixtures, and high-temperature reactor internals operating in oxidising or mixed gas atmospheres above 700°C.
Available Forged Product Forms — Jiangsu Liangyi
| Product Form | Max Size | Process | Typical End Uses |
|---|---|---|---|
| Open-die forged bars / billets | Ø up to 1,200 mm | Open die forging | Shaft blanks, fastener bar, disc blanks |
| Seamless rolled rings | OD up to 6,000 mm | Ring rolling | Turbine casings, flanges, bearing housings, seal rings |
| Forged sleeves / cylinders | OD up to 3,000 mm | Open die / mandrel | Pressure vessels, heavy-wall housing shells |
| Forged discs / blanks | OD up to 2,500 mm | Open die | Turbine discs, compressor discs |
| Profiled rings | OD up to 4,000 mm | Profile ring rolling | Flanged rings, labyrinth rings, guide rings |
| Custom forged shapes | Up to 30 tonnes | Multi-step open die | Valve bodies, complex structural forgings |
For dimensions, weights, tolerance grades, and current lead times, view available product forms and sizes on the 2.4654 product page.
How 2.4654 Compares to Related Superalloys
Engineers frequently evaluate 2.4654 against related Ni-Cr-Co alloys during material selection. The table below summarises the key differentiators for the five most commonly compared alternatives.
| Alloy | Cr% | Co% | Mo% | γ′ vol% | Max Service T | Strength | Key Trade-off |
|---|---|---|---|---|---|---|---|
| 2.4654 / NC20K14 ★ | ~20 | ~13 | ~4 | ~40% | ~1050°C | High | Best creep + oxidation balance in class |
| 2.4632 / Nimonic 90 | ~20 | ~17 | — | ~30% | ~920°C | Med-High | Higher Co content; lower peak strength than 2.4654 |
| 2.4952 / Nimonic 80A | ~20 | — | — | ~25% | ~815°C | Medium | No Co or Mo; lower cost; limited service temperature |
| 2.4663 / Alloy 617 | ~22 | ~12 | ~9 | <5% | ~1050°C | Medium | Solid-solution based; superior weldability in thick sections |
| Inconel 718 / 2.4668 | ~19 | — | ~3 | ~20% (γ″) | ~650°C | Very High (RT) | γ″ overages above 650°C; not for high-temperature service |
Choose 2.4654 when the design requires sustained creep resistance at 700–950°C combined with good oxidation protection and cyclic fatigue strength. Choose Inconel 718 / 2.4668 when maximum ambient-temperature tensile strength is the primary requirement and service temperature remains below ~650°C. Choose 2.4663 / Alloy 617 when thick-section weldability is a primary fabrication constraint alongside thermal stability above 900°C.
Sourcing Forged 2.4654 / NC20K14 Components
Procuring a nickel superalloy forging involves substantially more specification work than ordering structural steel. The table below lists the minimum information that should be resolved before issuing a request for quotation (RFQ) — missing any of these items typically results in scope clarification delays that extend lead times.
| Specification Element | What to Define in Your RFQ |
|---|---|
| Material standard | EN 10302:2008 (or equivalent); specify which property class (condition) applies |
| Delivery condition | Solution-annealed only, or solution-annealed + double aged; specify aging temperatures if non-standard |
| Dimensions & tolerances | Forging drawing or rough dimensions; DIN 7527 tolerance grade or custom class |
| Grain size | ASTM No. 5 or finer is typical; state explicitly if finer size is required for fatigue-critical components |
| NDE requirements | UT class per EN 10228-4; surface inspection (MT or PT) acceptance level |
| Certification level | EN 10204 Type 3.1 as minimum; 3.2 for nuclear or aerospace-qualified applications |
| Quantity & unit weight | Both required; determines heat lot size, forging process, and production schedule |
| Delivery condition (machining) | As-forged rough, semi-machined to stock, or finish-machined; specify bore/OD allowance if required |
Jiangsu Liangyi has supplied 2.4654 / NC20K14 components to customers across power generation, nuclear, and oil & gas in more than 50 countries for over 25 years. Standard lead times for open-die forgings: 6–10 weeks from approved drawing. Seamless rolled rings: 8–14 weeks depending on OD and section weight. To request a quote for 2.4654 forgings, send your drawing or rough dimensions and we will respond within 24 hours.
Frequently Asked Questions About 2.4654 / NC20K14
The following questions are among the most commonly raised by procurement engineers, materials engineers, and quality teams when specifying this alloy for the first time.
What is the difference between 2.4654 and NC20K14?
What is the maximum service temperature of 2.4654?
Is 2.4654 the same as Inconel 718?
What inspection documents are required for 2.4654 forgings?
Can 2.4654 be welded?
What grain size is required for 2.4654 turbine forgings?
Need 2.4654 / NC20K14 Forged Components?
Send your forging drawing or rough dimensions and we respond with a technical review and quotation within 24 hours. EN 10204 3.1 MTCs and UT results included as standard on every order.