Incoloy 909 Alloy
Low Thermal Expansion, High-Strength Nickel-Iron-Cobalt Superalloy
Supplied by Huaxiao-Alloy – Your Trusted Global Alloy Partner
Incoloy® 909 Alloy is a precipitation-hardenable nickel-iron-cobalt alloy specifically engineered to deliver an exceptionally low coefficient of thermal expansion (CTE) combined with high strength, excellent stress-relaxation resistance, and outstanding dimensional stability.
It is widely used in aerospace engines, gas turbines, precision mechanical systems, and high-performance structural components, where thermal mismatch, preload loss, and fatigue failure must be strictly controlled.
Huaxiao-Alloy supplies Incoloy 909 Alloy in all product forms, fully compliant with ASTM, AMS, ASME, and UNS standards, with complete traceability and export-grade quality control.
1. Incoloy 909 Alloy Overview
Incoloy 909 belongs to the family of controlled-expansion nickel alloys, positioned between Incoloy 907 and Incoloy 939-type high-strength superalloys. Its chemistry is optimized to achieve:
Very low thermal expansion
High yield and tensile strength after aging
Excellent stress relaxation resistance
Good fatigue and creep performance
Stable microstructure under thermal cycling
Compared with Incoloy 903 and 907, Incoloy 909 offers higher elevated-temperature strength while maintaining low expansion, making it ideal for engine hardware and preload-critical assemblies.
2. Chemical Composition (%)
| Element | Content (%) |
|---|---|
| Nickel (Ni) | 36.0 – 38.0 |
| Iron (Fe) | Balance |
| Cobalt (Co) | 12.0 – 15.0 |
| Chromium (Cr) | ≤ 0.50 |
| Niobium (Nb) | 4.5 – 5.2 |
| Titanium (Ti) | 1.2 – 1.7 |
| Aluminum (Al) | 0.3 – 0.6 |
| Carbon (C) | ≤ 0.03 |
| Manganese (Mn) | ≤ 0.50 |
| Silicon (Si) | ≤ 0.50 |
| Sulfur (S) | ≤ 0.015 |
📌 Metallurgical Principle
A Ni-Fe-Co low-expansion matrix combined with Nb-Ti-Al γ′ precipitation strengthening provides a rare combination of low CTE and high mechanical strength.
3. Mechanical Properties
Solution Annealed + Aged (Typical)
| Property | Value |
|---|---|
| Tensile Strength | ≥ 1350 MPa |
| Yield Strength (0.2%) | ≥ 950 MPa |
| Elongation | ≥ 10% |
| Hardness | 38 – 45 HRC |
| Fatigue Strength | Excellent |
| Stress Relaxation Resistance | Outstanding |
Mechanical properties vary with section size, product form, and heat-treatment condition.
4. Physical Properties
| Property | Value |
|---|---|
| Density | ~8.25 g/cm³ |
| Melting Range | 1340 – 1420°C |
| Coefficient of Thermal Expansion (20–300°C) | ~6.8 μm/m·K |
| Elastic Modulus | ~205 GPa |
| Electrical Resistivity | ~1.10 μΩ·m |
Key Advantage:
Incoloy 909 maintains dimensional accuracy under thermal cycling, outperforming most nickel-based superalloys in low-expansion performance.
5. Key Features & Advantages
📐 Ultra-Low Thermal Expansion
Minimizes thermal mismatch in multi-material assemblies.
💪 High Strength After Aging
Excellent load-bearing capability for engine and structural components.
🔩 Superior Stress Relaxation Resistance
Ideal for bolts, fasteners, flanges, and preload-critical joints.
🔁 Excellent Fatigue Performance
Reliable under cyclic loading and vibration.
6. Available Product Forms (Huaxiao-Alloy Supply)
Huaxiao-Alloy supplies Incoloy 909 Alloy in full range of standard and custom forms:
Long Products
Round bars
Square & flat bars
Forged bars
Shafts
Flat Products
Plates
Sheets
Strips
Tubular Products
Seamless mechanical tubes
Precision tubing
Precision & Custom Components
Aerospace fasteners
Structural rings
Engine hardware
CNC-machined precision parts
7. Standards & Equivalent Grades
| Standard | Designation |
|---|---|
| UNS | N19909 |
| ASTM | B637 |
| AMS | AMS 5709 / AMS 5711 |
| ASME | SB-637 |
| EN / DIN | Available upon request |
📄 Certifications: EN 10204 3.1 / 3.2, PMI, full heat traceability
8. Corrosion & Oxidation Behavior
Incoloy 909 is not designed for aggressive corrosion service like Inconel 625 or Incoloy 925. However, it provides:
Good resistance to atmospheric corrosion
Stable oxidation resistance at moderate temperatures
Excellent environmental stability in controlled aerospace and industrial environments
Material selection support is recommended for chemically aggressive conditions.
9. Typical Applications
Aerospace & Aviation
Jet engine structural components
Engine casings and rings
High-strength fasteners
Preload-critical joints
Gas Turbine & Energy
Turbine support structures
Generator components
High-precision rotating parts
Precision Engineering
Low-expansion shafts
Thermal cycling assemblies
Dimension-critical mechanical systems
Defense & Advanced Manufacturing
Fatigue-critical structural assemblies
High-performance mechanical hardware
10. Heat Treatment & Fabrication Guide
Heat Treatment
Solution annealing: ~980°C, air cool
Aging: 720–760°C for precipitation strengthening
Machining
Best performed in solution-annealed condition
Carbide tooling recommended
Welding
GTAW / GMAW suitable
Weld in annealed condition
Post-weld aging required to restore full strength
11. Quality Control & Inspection
Huaxiao-Alloy ensures:
Chemical composition verification
Mechanical & hardness testing
Ultrasonic & surface inspection
Heat-treatment validation
PMI testing
Dimensional inspection
Full mill test certificates & traceability
12. Why Choose Huaxiao-Alloy for Incoloy 909?
✔ Aerospace-grade certified mills
✔ Stable long-term supply
✔ Custom forging & machining
✔ Precision heat treatment control
✔ Export-ready packaging
✔ Technical alloy selection support
📍 Production & Stock: Wuxi · Foshan · Shanghai Baoshan
🌍 Global Export: North America · Europe · Middle East · Asia-Pacific
Incoloy 909 offers higher strength and better elevated-temperature performance while maintaining low thermal expansion.
Yes. It is widely used in engine hardware and preload-critical aerospace components.
Yes, aging is essential to achieve full mechanical properties.
It offers moderate corrosion resistance but is not intended for aggressive chemical environments.
Yes, AMS-certified material is available on request.
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