01 — Overview

A Superalloy Engineered for Fabricability Without Sacrificing Performance

Nimonic C263 — also designated UNS N07263 and W.Nr. 2.4650 — is a precipitation-hardenable nickel-cobalt-chromium-molybdenum superalloy developed in 1971 by Rolls-Royce Ltd. as a direct successor to Nimonic 80A. The engineering brief was specific: create an alloy capable of robust elevated-temperature performance while being far easier to form, weld, and fabricate than the dominant high-strength superalloys of the era.

Where Waspaloy and René 41 offered peak high-temperature strength, they were notoriously difficult to fabricate without cracking. Nimonic C263 broke this compromise through a carefully balanced chemistry: chromium for oxidation resistance, cobalt for solid-solution strengthening, molybdenum for creep resistance, and a controlled titanium-to-aluminum ratio that produces a moderate gamma-prime (γ′) precipitate volume fraction — enough for strength, but not so much as to cause strain-age cracking during welding and post-weld heat treatment.

Today Nimonic C263 is a globally recognised material in aerospace, power generation, and industrial processing. It operates reliably at temperatures up to 900°C (1,650°F) over thousands of service hours under significant mechanical stress, and is available in all wrought forms including precision forgings. Engineers and procurement teams sourcing custom Nimonic C263 open-die forgings and seamless rolled rings can find full product specifications, available shapes, certifications, and pricing on our dedicated product page.

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Key Advantage: Nimonic C263 is one of the very few gamma-prime-strengthened nickel superalloys that is not normally susceptible to strain-age cracking (SAC) — the catastrophic weld-zone failure that disqualifies most other high-strength superalloys from use in welded assemblies.

Alternative Designations

Nimonic® is a registered trademark of Special Metals Corporation. All alloy designations on this page are used for informational and technical reference purposes only. This page is published by Jiangsu Liangyi Co., Limited — an independent manufacturer — and is not affiliated with or endorsed by Special Metals Corporation or its successors.

All of the following names refer to the same alloy and can be used interchangeably on drawings and purchase orders:

  • Nimonic C263 / Nimonic® 263 / Nimonic Alloy C263
  • Alloy 263 / Alloy C263
  • UNS N07263
  • W.Nr. 2.4650 (German Werkstoff Number)
  • BS HR 1, HR 5 (British Standard)
02 — Metallurgy

Chemical Composition & Elemental Roles

The chemistry of Nimonic C263 is precisely engineered to balance four competing objectives: high-temperature strength, oxidation resistance, phase stability, and fabricability. Each element plays a specific metallurgical role.

Element Symbol Min wt% Max wt% Role in Alloy
NickelNiBalance—Austenitic FCC matrix (γ-phase); base corrosion resistance
ChromiumCr19.021.0Oxidation & hot-corrosion resistance; solid-solution strengthening
CobaltCo19.021.0Solid-solution strengthening; raises γ′ solvus temperature
MolybdenumMo5.66.1Solid-solution & creep strengthening; improves stress-rupture life
TitaniumTi1.92.4Primary γ′ precipitate former Ni₃(Al,Ti); strengthening
AluminumAl0.30.6Secondary γ′ former; oxidation resistance via Al₂O₃ scale
CarbonC0.040.08M₂₃C₆ carbide precipitation; grain-boundary pinning
IronFe—0.70Residual element; controlled for alloy purity
ManganeseMn—0.60Deoxidiser during melting; controls sulphur
SiliconSi—0.40Deoxidiser; controlled to prevent embrittlement
CopperCu—0.20Residual; kept low to preserve corrosion integrity
BoronB—0.005Grain-boundary cohesion; enhances creep rupture life

Major Alloying Additions (by approximate midpoint wt%)

Nickel (Bal.)
~52 %
Chromium
20 %
Cobalt
20 %
Molybdenum
5.85 %
Titanium
2.15 %
Aluminum
0.45 %
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Why is the Ti:Al ratio so important? Nimonic C263 deliberately maintains a high titanium-to-aluminium ratio (~5:1) while keeping absolute aluminium content low. This limits the gamma-prime (γ′) volume fraction to approximately 12–18%, compared to 25–40% in stronger alloys like Waspaloy or René 41. The lower precipitate density is precisely what makes C263 resistant to strain-age cracking — a defining advantage for welded turbine assemblies.

03 — Mechanical Data

Mechanical & Physical Properties

Properties listed are representative values for solution-treated and age-hardened material. Consult lot-specific MTC 3.2 certificates for certified values. Actual results vary by product form, section size, and heat treatment parameters.

Tensile Strength (RT)
≥ 940 MPa minimum · ~136 ksi
0.2% Proof Stress (RT)
≥ 590 MPa minimum · ~86 ksi
Elongation (RT)
≥ 20 % in 50 mm gauge length
Hardness
~200 BHN (Brinell)
Density
8.36 g/cm³ · 0.302 lb/in³
Elastic Modulus (RT)
~222 GPa · 32.2 × 10⁶ psi
Max Service Temperature
900 °C 1,650 °F oxidation limited
Thermal Expansion
~14.0 µm/m·°C from 20–800 °C

High-Temperature Tensile Properties (Typical, Solution Treated + Aged)

Test Temperature UTS (MPa) 0.2% PS (MPa) Elongation % Reduction of Area %
20 °C (Room Temp)980–1,050620–68024–3038–46
400 °C (752 °F)880–950590–64020–2734–44
600 °C (1,112 °F)860–930570–62019–2632–42
700 °C (1,292 °F)820–890550–61018–2530–40
800 °C (1,472 °F)680–760480–55016–2225–35
900 °C (1,652 °F)300–420230–31014–2022–32

All Nimonic C263 forgings manufactured to AMS 5886 and ASTM B637 at Jiangsu Liangyi undergo this two-stage heat treatment cycle in-house, with furnace records and time-temperature charts supplied as part of the MTC documentation.

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Creep & Stress Rupture: Nimonic C263 delivers a 1,000-hour stress-rupture life of approximately 185–205 MPa at 750 °C and 90–110 MPa at 815 °C. Creep resistance remains effective up to approximately 850 °C for structural applications under moderate load — suitable for combustor liners, transition pieces, and turbine rings in both aero and industrial gas turbines.

04 — Processing

Heat Treatment Procedures

Nimonic C263 is supplied in the annealed condition and must undergo a two-stage heat treatment to develop full mechanical properties. Parameters vary by product form and section thickness.

1

Solution Treatment (Annealing)

The material is heated to dissolve all gamma-prime precipitates and carbide phases into the nickel matrix, producing a homogeneous austenitic microstructure. Rapid quenching immediately follows to suppress re-precipitation during cooling.

1,150 °C / 2,102 °F 1.5–2.5 h (bar / billet) Water Quench
2

Age Hardening (Precipitation Treatment)

Fine coherent Ni₃(Al,Ti) gamma-prime particles precipitate throughout the matrix during the aging cycle. This dramatically increases tensile strength, proof stress, and creep resistance while preserving acceptable ductility for structural use.

800 °C / 1,472 °F 8 hours Air Cool
3

Post-Weld or Post-Form Anneal (When Required)

After welding or extensive cold working, a full solution anneal before re-aging relieves residual stresses and restores microstructural homogeneity. Unlike most gamma-prime alloys, Nimonic C263 typically completes this cycle without strain-age cracking.

1,150 °C → WQ → 800 °C / 8 h → AC
Product Form Solution Treatment Quench Age
Forged / Extruded Bar1,150 °C / 1.5–2.5 hWater800 °C / 8 h / AC
Hot-Rolled Sheet1,150 °C / 1.5 hWater800 °C / 8 h / AC
Cold-Rolled Sheet & Tube1,150 °C / 3–10 minFan / Water800 °C / 8 h / AC
Large Forgings1,150 °C / 2–4 hWater / Fan800 °C / 8 h / AC
05 — Manufacturing

Forging Nimonic C263: Process & Capabilities

Forging is the preferred manufacturing route for structural C263 components, producing a refined grain structure that maximises fatigue resistance, tensile strength, and stress-rupture life compared to castings.

Step 01 Melting & Refining
EAF + VIM / VAR
Step 02 Billet Conditioning
UT Inspection
Step 03 Hot Forging
950–1,100 °C
Step 04 Heat Treatment
Solution + Age
Step 05 NDE, Machining
& Certification

Available Forging Forms

Open Die Blocks, discs, flanges, sleeves, hollow bars, and custom billets up to very large sizes. Hydraulic forging presses up to 6,000 tons. Best for low-to-medium volume and large cross-sections.
Closed Die Near-net-shape components with complex geometries and tight dimensional tolerances. Reduces downstream machining stock significantly. Best for medium-to-high volume production.
Rolled Rings Seamless rolled rings from 300 mm to 5,000 mm OD. Ideal for turbine casings, combustor rings, flanges, and bearing races. Superior circumferential grain flow vs machined-from-billet approach.
Custom NNS Near-net-shape forgings designed collaboratively with OEM engineering teams. Minimises material yield loss and reduces total machining hours for high-value components.
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Machining Nimonic C263: C263 is classified as difficult to machine due to its high work-hardening rate and low thermal conductivity. Key practices: use rigid setups, sharp carbide tooling (replace frequently), positive rake angles, high cutting-fluid flow, consistent chip load, and never allow surface glazing. Typical stock removal rates: 20–30 SFM (HSS) or 80–100 SFM (carbide).

06 — Industries & End Uses

Where Nimonic C263 Is Used

The alloy's unique balance of fabricability, weldability, and high-temperature performance makes it the material of choice across multiple demanding industries.

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Aerospace Turbine Engines

Combustor assemblies, transition liners, turbine rings, hot-section structural frames, and flame tubes in military and commercial aero-engines. C263 is particularly valued where welded construction meets high-temperature service.

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Land-Based Power Gas Turbines

Transition ducts, combustor panels, turbine casings, sealing rings, and hot-gas-path hardware in industrial gas turbines for electricity generation. Resistance to thermal cycling is a key benefit here.

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Steam Turbine Components

Turbine discs, blading, and high-pressure fasteners for advanced steam cycles operating at elevated temperatures in coal and nuclear power plants where long-term creep resistance is mandatory.

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Rocket & Space Propulsion

Nozzle hardware, thrust chamber components, and turbopump parts where short-duration extreme thermal loads combine with oxidising environments. The alloy's weldability enables complex fabricated assemblies.

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Chemical & Petrochemical Processing

High-temperature reactor vessels, heat-exchanger tubing, and pressure-bearing components in process environments combining elevated temperature with corrosive chemical streams.

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Nuclear Energy Systems

Structural components in advanced high-temperature reactor concepts and heat-exchange hardware where both radiation resistance and elevated-temperature mechanical performance are required simultaneously.

For full details on available shapes, weights, certifications, and delivery lead times, visit Jiangsu Liangyi's certified UNS N07263 forged parts product page — covering everything from 30 kg prototype forgings to 30,000 kg production runs.

07 — Alloy Selection

Nimonic C263 vs. Competing Superalloys

Choosing the right nickel superalloy involves balancing performance, fabrication constraints, and cost. Nimonic C263 occupies a well-defined niche: moderate-to-high temperature performance with exceptional fabricability.

Property / Criterion Nimonic C263 Waspaloy René 41 Nimonic 80A Haynes 282
Max Service Temp. 900 °C980 °C980 °C815 °C1,000 °C
Weldability Excellent Moderate Difficult Good Very Good
Cold Formability Excellent Moderate Difficult Good Good
Strain-Age Cracking Risk Very Low Moderate High Low Low
Creep Resistance (≤900 °C) Good Very Good Excellent Moderate Excellent
Oxidation Resistance Good (to 900 °C) Very Good Good Good Excellent
Relative Material Cost Moderate High Very High Moderate-Low High
Forging Difficulty Moderate Moderate-High High Moderate Moderate
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When to choose C263: Select Nimonic C263 when your design requires welded assemblies, complex formed geometries, or when fabrication yield and downstream processing cost are as important as raw mechanical performance. If maximum high-temperature strength is the sole criterion, Waspaloy or René 41 may be appropriate despite their processing challenges and higher cost.

08 — Compliance & Certification

Standards, Specifications & Certifications

Nimonic C263 forgings and wrought products are manufactured to a range of international specifications. The applicable standard depends on the end use, regional regulatory framework, and customer-specific requirements.

AMS 5886 SAE aerospace material specification for Nimonic C263 bars, forgings, and rings. The primary aerospace procurement standard in North America.
AMS 5872 SAE aerospace material specification for Nimonic C263 sheet, strip, and plate forms.
ASTM B637 Standard specification for precipitation-hardening nickel alloy bars, forgings, and forging stock for high-temperature service.
BS HR 1 / HR 5 British Standard specifications for Nimonic alloy 263 in various wrought forms; widely referenced in UK and European aerospace supply chains.
EN 2991 European Aerospace Standard for Nimonic alloy C263 bar and sections for aerospace structural applications.
W.Nr. 2.4650 German Werkstoff-Nummer designation used in DIN-based European industrial specifications and component drawings.
UNS N07263 Unified Numbering System designation (SAE/ASTM) used as the authoritative alloy identifier across all US and international standards.
MTC 3.2 EN 10204 Type 3.2 Mill Test Certificate — third-party co-signed certification of chemical and mechanical test results. Widely required by aerospace OEMs; Jiangsu Liangyi provides MTC documentation in cooperation with accredited inspection bodies.
09 — Common Questions

Frequently Asked Questions

What is the difference between Nimonic C263 and Alloy 263?

There is no difference — they are the same material. "Nimonic C263," "Alloy 263," "Nimonic 263," "UNS N07263," and "W.Nr. 2.4650" are all interchangeable designations for the same nickel-cobalt-chromium-molybdenum superalloy. "Nimonic" was originally a trade name used by Special Metals / Inco, while "C263" is the internal alloy code. All major standards and procurement documents treat these as equivalent.

Can Nimonic C263 be used above 900 °C?

Sustained structural use above 900 °C is generally not recommended. Above this temperature, gamma-prime precipitates dissolve and coarsen rapidly, causing significant strength loss. Oxidation resistance is adequate up to approximately 925 °C in clean air. For higher service temperatures, consider alloys such as Haynes 282, Waspaloy, or single-crystal superalloys. Short-duration excursions above 900 °C may be tolerated depending on stress level and application context.

Why is Nimonic C263 preferred for welded turbine assemblies?

Most high-strength gamma-prime nickel superalloys are susceptible to strain-age cracking (SAC) during post-weld heat treatment. As the constrained weld region contracts on cooling through the age-hardening range, residual stresses exceed the material's ductility, causing intergranular cracking. Nimonic C263's lower gamma-prime volume fraction — achieved by keeping aluminium content deliberately low — means precipitation kinetics are less aggressive, giving the alloy enough ductility to accommodate weld residual stresses without cracking.

Which welding processes are compatible with Nimonic C263?

TIG (GTAW), GMAW (MIG), electron-beam welding (EBW), and resistance welding are all suitable. Oxyacetylene and submerged-arc welding are not recommended. Use matching C263 filler metal when filler is required. Preheat is generally not needed, but excessive heat input should be avoided. After welding, a full solution anneal followed by re-aging is recommended for structural joints.

What certifications should I require when purchasing Nimonic C263 forgings?

At minimum, require an EN 10204 Type 3.2 Mill Test Certificate (MTC 3.2) co-signed by an accredited third-party inspector (Bureau Veritas, SGS, TÜV, or equivalent). The MTC should confirm chemical composition, mechanical test results, heat treatment records, applicable specification compliance (e.g., AMS 5886, ASTM B637), and full heat/lot traceability. For critical aerospace applications, we recommend also requesting sample Mill Test Certificates and verification of the supplier's in-house testing capabilities before placing orders.

What is the minimum order for Nimonic C263 forgings?

Minimum order quantities vary by manufacturer and forging type. Most capable forging suppliers accept single-piece prototype orders for open-die forgings and rolled rings, with unit pricing reflecting setup costs. For production quantities, pricing improves at 5+ and 20+ pieces. Contact your supplier with your drawing, material specification (e.g., AMS 5886), required certifications, and delivery timeline for an accurate quotation.