Nimonic 263
Introduction to Nimonic 263
Nimonic 263 is a precipitation-hardenable nickel-cobalt-chromium-molybdenum alloy engineered for outstanding strength, ductility, and corrosion resistance in high-temperature environments. Developed for applications requiring superior weldability and fabricability, it is used extensively in aerospace and gas turbine components operating up to 900°C. The alloy's stable microstructure and resistance to thermal fatigue make it ideal for combustor parts, turbine casings, and afterburner components.
Precision manufacturing of this alloy is often performed through CNC machining services to meet strict dimensional and geometric tolerances. CNC machining offers the repeatability and process control required for complex parts that endure cyclic thermal and mechanical loads.
Chemical, Physical, and Mechanical Properties of Nimonic 263
Nimonic 263 (UNS N07263 / W.Nr. 2.4650) is a high-strength wrought superalloy with a balanced composition that maintains mechanical integrity at elevated temperatures while allowing good formability and weldability.
Chemical Composition (Typical)
Element | Composition Range (wt.%) | Key Role |
|---|---|---|
Nickel (Ni) | Balance (~50.0) | Base matrix, provides oxidation resistance |
Cobalt (Co) | 19.0–21.0 | Improves creep and thermal fatigue strength |
Chromium (Cr) | 19.0–21.0 | Forms Cr₂O₃ oxide layer, improves oxidation resistance |
Molybdenum (Mo) | 5.6–6.1 | Strengthens via solid solution hardening |
Iron (Fe) | ≤0.7 | Residual element |
Titanium (Ti) | 1.9–2.4 | Promotes γ′ phase strengthening |
Aluminum (Al) | 0.6–0.8 | Contributes to precipitation hardening |
Carbon (C) | ≤0.06 | Forms carbides to improve creep resistance |
Manganese (Mn) | ≤0.6 | Enhances hot workability |
Silicon (Si) | ≤0.4 | Supports oxidation resistance |
Boron (B) | ≤0.005 | Grain boundary strengthening |
Zirconium (Zr) | ≤0.06 | Enhances creep rupture strength |
Physical Properties
Property | Value (Typical) | Test Standard/Condition |
|---|---|---|
Density | 8.36 g/cm³ | ASTM B311 |
Melting Range | 1325–1375°C | ASTM E1268 |
Thermal Conductivity | 11.3 W/m·K at 100°C | ASTM E1225 |
Electrical Resistivity | 1.10 µΩ·m at 20°C | ASTM B193 |
Thermal Expansion | 13.4 µm/m·°C (20–1000°C) | ASTM E228 |
Specific Heat Capacity | 435 J/kg·K at 20°C | ASTM E1269 |
Elastic Modulus | 212 GPa at 20°C | ASTM E111 |
Mechanical Properties (Solution Treated + Aged)
Property | Value (Typical) | Test Standard |
|---|---|---|
Tensile Strength | 1000–1100 MPa | ASTM E8/E8M |
Yield Strength (0.2%) | 700–800 MPa | ASTM E8/E8M |
Elongation | ≥20% | ASTM E8/E8M |
Hardness | 220–250 HB | ASTM E10 |
Creep Rupture Strength | 180 MPa at 815°C (1000h) | ASTM E139 |
Fatigue Resistance | Excellent | ASTM E466 |
Key Characteristics of Nimonic 263
Excellent High-Temperature Ductility Unlike many precipitation-hardened alloys, Nimonic 263 maintains elongation >20% at elevated temperatures, providing reliable formability and reduced risk of cracking under thermal stress.
Good Weldability Designed for weld repair and fabrication, it resists hot cracking and maintains strength in the heat-affected zone (HAZ).
Oxidation Resistance Chromium and aluminum allow the formation of a stable protective oxide layer, effective up to 980°C in oxidizing atmospheres.
Creep and Fatigue Strength Long-term creep rupture strength of 180 MPa at 815°C ensures performance in cyclic thermal loads, ideal for combustor liners and turbine support structures.
Gamma Prime Strengthening with Stability A controlled γ′ phase distribution ensures a balance between high strength and formability, especially after welding or secondary machining.
CNC Machining Challenges and Solutions for Nimonic 263
Machining Challenges
Tool Wear and Edge Chipping
High-temperature strength and solid solution-strengthening agents accelerate flank and crater wear on standard tools.
Heat Generation
Poor heat conduction concentrates thermal load in the cutting zone, requiring cooling strategies to avoid distortion.
Strain Hardening
The alloy exhibits moderate work hardening, increasing surface hardness by up to 25% during machining.
Optimized Machining Strategies
Tool Selection
Parameter | Recommendation | Rationale |
|---|---|---|
Tool Material | Carbide (K20–K30), PCD or ceramic for finishing | High resistance to thermal softening |
Coating | AlTiN or TiSiN (3–5 µm) | Reduces friction and thermal impact |
Geometry | Positive rake angle (6–10°), honed edge (~0.05 mm) | Controls built-up edge and vibration |
Cutting Parameters (ISO 3685 Compliant)
Operation | Speed (m/min) | Feed (mm/rev) | Depth of Cut (mm) | Coolant Pressure (bar) |
|---|---|---|---|---|
Roughing | 12–20 | 0.15–0.25 | 2.0–3.0 | 100–120 |
Finishing | 25–35 | 0.05–0.10 | 0.3–1.0 | 120–150 |
Surface Treatment for Machined Nimonic 263 Parts
Hot Isostatic Pressing (HIP)
HIP ensures the elimination of internal voids and enhances fatigue life by >25%, which is crucial for rotating components.
Heat Treatment
Heat Treatment includes solution annealing at ~1145°C and aging at ~800°C to refine γ′ distribution and improve creep strength.
Superalloy Welding
Superalloy Welding provides crack-free joints with minimal reduction in strength across weld zones, using matching composition filler wire.
Thermal Barrier Coating (TBC)
TBC Coating reduces component surface temperature by up to 200°C, prolonging the service life of combustor and turbine structures.
Electrical Discharge Machining (EDM)
EDM enables microfeature creation and precision hole drilling without inducing residual stresses in heat-sensitive areas.
Deep Hole Drilling
Deep Hole Drilling achieves Ra <1.6 µm and L/D >30:1 in cooling channels with minimal runout (<0.3 mm/m).
Material Testing and Analysis
Material Testing covers mechanical testing (tensile, creep), XRD phase analysis, microstructural verification, and ultrasonic flaw detection per ASME.
Industry Applications of Nimonic 263 Components
Aerospace Combustor Systems: Liners, seals, transition ducts, and burner cans operating in cyclic thermal environments.
Power Generation: Gas turbine components such as seals, fuel nozzles, and combustor tiles.
Nuclear Reactors: High-temperature-resistant bolting and pressure vessel hardware in radiation zones.
Automotive Turbo Systems: Turbocharger housings, manifolds, and heat shields exposed to exhaust gases.
Industrial Heating Systems: High-strength flanges, fittings, and expansion bellows in furnace assemblies.
FAQs
What are the best CNC cutting strategies for minimizing wear while machining Nimonic 263?
How does Nimonic 263’s weldability impact the post-machining process for complex assemblies?
What thermal treatments are necessary after CNC machining to optimize the mechanical properties of Nimonic 263 parts?
How does Nimonic 263 compare with other nickel alloys regarding fatigue and oxidation resistance under cyclic loading?
What material testing and inspection standards are applied to validate CNC-machined Nimonic 263 components?
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