⚡ Quick Specs: Incoloy 901
What Is Incoloy 901?
Incoloy 901 (UNS N09901 / W.Nr. 2.4662) is an age-hardenable iron-nickel-base superalloy strengthened by gamma-prime (γ′ – Ni₃(Ti,Al)) precipitation. Developed as a lower-cost alternative to nickel-base turbine disc alloys, it offers an excellent combination of high-temperature strength, creep resistance, and good fabricability at temperatures up to 650 °C (1200 °F).
What makes Incoloy 901 unique among Incoloy grades is its high titanium and aluminum content (~3.0% Ti + ~0.2% Al), which provides substantial precipitation hardening through gamma-prime formation in an iron-nickel matrix. This gives it mechanical properties approaching nickel-base superalloys at a fraction of the raw material cost. As an Incoloy 901 manufacturer and supplier, Hangbo Alloy Group delivers the grade in forged bar, ring, disc, and machined component forms for aerospace gas turbines, industrial gas turbines, and high-temperature fastening applications.
Chemical Composition
Nominal composition of Incoloy 901 per UNS N09901. All values in weight percent (wt%).
| Element | Min (wt%) | Max (wt%) |
|---|---|---|
| Nickel (Ni) | 40.0 | 45.0 |
| Chromium (Cr) | 11.0 | 14.0 |
| Iron (Fe) | Balance | Balance |
| Titanium (Ti) | 2.35 | 3.10 |
| Molybdenum (Mo) | 5.0 | 6.5 |
| Aluminum (Al) | — | 0.35 |
| Manganese (Mn) | — | 1.0 |
| Silicon (Si) | — | 0.60 |
| Carbon (C) | — | 0.10 |
| Boron (B) | 0.01 | 0.02 |
| Copper (Cu) | — | 0.50 |
| Sulfur (S) | — | 0.030 |
Physical Properties
| Property | Value | Unit |
|---|---|---|
| Density | 8.14 | g/cm³ |
| Melting Range | 1280 – 1345 | °C |
| Specific Heat (20 °C) | 450 | J/kg·K |
| Thermal Conductivity (20 °C) | 11.5 | W/m·K |
| Electrical Resistivity (20 °C) | 1.15 | μΩ·m |
| Young's Modulus (20 °C) | 200 | GPa |
| Mean CTE (20–100 °C) | 13.0 | μm/m·°C |
Mechanical Properties
| Property | Typical Value |
|---|---|
| Tensile Strength (Rm, fully heat treated) | ≥ 1035 MPa (≥ 150 ksi) |
| Yield Strength (Rp0.2, fully heat treated) | ≥ 760 MPa (≥ 110 ksi) |
| Elongation (A%, fully heat treated) | ≥ 15% |
| Reduction of Area (fully heat treated) | ≥ 18% |
| Hardness (fully heat treated) | 28 – 38 HRC |
| Creep Rupture (650 °C / 100 h) | ~380 MPa |
High-Temperature Performance
- Creep resistance: Incoloy 901 offers excellent creep-rupture properties up to 650 °C, with a 100-hour rupture stress of approximately 380 MPa at 650 °C — competitive with nickel-base disc alloys at significantly lower material cost.
- Stress relaxation: The alloy maintains high clamping force in bolted joints at elevated temperatures, making it especially suitable for turbine casing fasteners and flange bolting.
- Tensile strength retention: Retains approximately 75% of room-temperature yield strength at 540 °C and 55% at 650 °C, providing reliable mechanical performance across the gas turbine operating envelope.
- Thermal stability: The gamma-prime strengthening phase is stable up to 650 °C. Prolonged exposure above this temperature causes over-aging and gradual strength loss, defining the alloy's practical temperature ceiling.
Corrosion Resistance
- High-temperature oxidation: Offers good oxidation resistance in air and combustion gases up to 815 °C (1500 °F) for intermittent exposure, and 705 °C (1300 °F) for continuous service, thanks to its 11–14% chromium content.
- Hot corrosion (sulfidation): Moderate resistance to Type I (high-temperature) hot corrosion from sodium sulfate deposits at 850–950 °C. For Type II (low-temperature) hot corrosion below 750 °C, higher-chromium alloys may be preferred in severe marine/industrial environments.
- Aqueous corrosion: While designed for high-temperature service, Incoloy 901 offers moderate general corrosion resistance in non-aggressive environments. It is not recommended for strongly acidic or chloride-rich aqueous service.
Applications
| Application Area | Typical Components & Notes |
|---|---|
| Gas Turbine Discs | Compressor and turbine discs, shafts, and spacer rings in aero and industrial gas turbines where 650 °C creep strength is critical |
| Turbine Shafts & Rotors | High-speed rotating shafts requiring high strength-to-weight ratio and good fatigue resistance |
| High-Temperature Fasteners | Turbine casing bolts, studs, and nuts; flange bolting for steam turbines and high-temperature pressure vessels |
| Afterburner Components | Flame holders, spray rings, and liner components in military engine afterburners (reheat systems) |
| Turbocharger Rotors | Diesel engine turbocharger turbine wheels operating at 600–700 °C exhaust gas temperatures |
| Springs & Seals | High-temperature springs, Belleville washers, and metal seals in turbine and aerospace applications |
Available Product Forms
| Product Form | Typical Dimensions & Specifications |
|---|---|
| Forged Bar & Billet (AMS 5660) | φ 12 – φ 500 mm, hot-worked, solution treated, stabilized, and aged |
| Forgings & Rings (AMS 5661) | Turbine discs, shafts, rings, and custom forgings up to 1500 mm OD |
| Fasteners & Bolting | Studs, bolts, nuts, and washers per turbine OEM specifications, fully heat treated |
| Machined Components | Finish-machined discs, shafts, and high-temperature structural parts to customer drawing |
Heat Treatment
| Step | Temperature | Cooling | Purpose |
|---|---|---|---|
| Solution Treatment | 1095 ± 15 °C (2000 ± 25 °F) | Water quench | Dissolve all phases; prepare uniform grain structure |
| Stabilization | 790 ± 10 °C (1450 ± 20 °F) | Hold 2–4 h, air cool | Precipitate controlled gamma-prime at grain boundaries for notch ductility |
| Aging | 730 ± 10 °C (1350 ± 20 °F) | Hold 24 h, air cool | Achieve full gamma-prime strengthening throughout grain interiors |
Related Standards & Specifications
| Standard | Product Scope / Notes |
|---|---|
| UNS | N09901 |
| DIN / W.Nr. | 2.4662 |
| AMS 5660 | Bars, forgings, and rings (solution + precipitation heat treated) |
| AMS 5661 | Bars, forgings, and rings (alternative heat treatment) |
| BS HR 53 | Ni-Fe-Cr-Mo-Ti-Al heat-resisting alloy bars (UK) |
| AECMA prEN 2179 | European aerospace material standard |
Frequently Asked Questions (FAQ)
1. What is Incoloy 901?
Incoloy 901 (UNS N09901 / W.Nr. 2.4662) is an age-hardenable iron-nickel-base superalloy containing 40–45% nickel, 11–14% chromium, 5.0–6.5% molybdenum, and 2.35–3.10% titanium. It achieves high strength through gamma-prime (Ni₃(Ti,Al)) precipitation during a three-step heat treatment, making it suitable for gas turbine discs, shafts, fasteners, and afterburner components operating at up to 650 °C.
2. What is the chemical composition of Incoloy 901?
Nominal Incoloy 901 composition (wt%): Ni 40.0–45.0, Cr 11.0–14.0, Fe balance, Mo 5.0–6.5, Ti 2.35–3.10, Al ≤0.35, Mn ≤1.0, Si ≤0.60, C ≤0.10, B 0.01–0.02. The high titanium content provides gamma-prime strengthening, while boron improves grain boundary ductility and creep rupture life.
3. What is the density and melting range of Incoloy 901?
Incoloy 901 has a density of approximately 8.14 g/cm³ (0.294 lb/in³) and a melting range of about 1280–1345 °C (2335–2450 °F). This is slightly lighter than full nickel-base disc alloys such as Waspaloy (8.23 g/cm³), giving a small weight advantage in rotating components.
4. What are the mechanical properties of Incoloy 901?
In the fully heat-treated condition: minimum tensile strength 1035 MPa (150 ksi), minimum 0.2% yield strength 760 MPa (110 ksi), minimum elongation 15%, hardness 28–38 HRC. At 650 °C, tensile strength remains above 750 MPa, giving Incoloy 901 one of the best strength-to-cost ratios among high-temperature disc materials.
5. What is the heat treatment for Incoloy 901?
Standard three-step heat treatment: (1) Solution treat at 1095 ± 15 °C (2000 ± 25 °F), water quench; (2) Stabilize at 790 ± 10 °C (1450 ± 20 °F) for 2–4 hours, air cool — this precipitates grain-boundary gamma-prime for improved notch ductility and creep resistance; (3) Age at 730 ± 10 °C (1350 ± 20 °F) for 24 hours, air cool — this completes gamma-prime precipitation for maximum strength.
6. What is the maximum service temperature of Incoloy 901?
Incoloy 901 maintains useful mechanical properties up to about 650 °C (1200 °F) in rotating disc applications. Above 650 °C, gamma-prime coarsening accelerates and strength drops significantly. For 650–750 °C service, nickel-base alloys such as Waspaloy or Udimet 720 are typically specified.
7. How does Incoloy 901 compare to Waspaloy?
Both are age-hardenable turbine disc alloys, but Incoloy 901 contains significantly less nickel (40–45% vs ~58%) and is iron-based rather than nickel-based. This gives Incoloy 901 a ~30% raw material cost advantage but limits its maximum service temperature to ~650 °C versus Waspaloy's ~870 °C. For moderate-temperature discs and fasteners, Incoloy 901 offers an excellent cost-performance balance.
8. Can Incoloy 901 be welded?
Incoloy 901 has limited weldability due to its high titanium content and gamma-prime hardening. It can be welded using GTAW and GMAW with matching filler, but requires careful preheat, controlled interpass temperature, and full post-weld solution treatment + aging to restore properties. Welding is generally avoided on finished, heat-treated components.
9. What are the typical applications of Incoloy 901?
Primary applications: gas turbine compressor and turbine discs and shafts; aerospace and land-based turbine casing fasteners and flange bolting; military engine afterburner flame holders and spray rings; diesel turbocharger turbine rotors; and high-temperature springs and metal seals in aerospace systems.
10. What standards apply to Incoloy 901?
Key standards: AMS 5660 (bars, forgings, rings — solution + precipitation heat treated), AMS 5661 (alternative heat treatment), BS HR 53 (bars, UK aerospace), and AECMA prEN 2179 (European). Material is supplied with EN 10204 3.1 or 3.2 certification as required.
11. What product forms are available for Incoloy 901?
Hangbo Alloy supplies Incoloy 901 in forged bar and billet (φ 12–500 mm), forged discs and rings, turbine shafts, high-temperature fasteners (studs, bolts, nuts), and custom machined components. Typical specifications include AMS 5660 and AMS 5661.
12. How much does Incoloy 901 cost?
Incoloy 901 is one of the most economical turbine disc superalloys, typically priced 25–35% below nickel-base alternatives such as Waspaloy or Udimet 720 due to its lower nickel content and iron-base matrix. Lead times for standard mill products are 4–8 weeks; forged-to-shape discs and machined components require engineering review. Contact Hangbo Alloy at hangbo@nickel-alloy.com for a current quotation.
Need Incoloy 901 for Turbine Discs, Shafts, or High-Temperature Fasteners?
Hangbo Alloy Group is a trusted global manufacturer and supplier of Incoloy 901 (UNS N09901 / 2.4662) in forged bar, ring, disc, and fastener forms. Aerospace-grade AMS 5660/5661 certified, full traceability, and competitive pricing.