A286 (UNS S66286, also known as grade 660) is an iron-based superalloy that is precipitation-hardened to achieve high strength and oxidation resistance up to 700°C (1292°F). Unlike nickel-based superalloys such as Inconel 718, A286 offers a lower cost while still providing excellent creep resistance and tensile strength, making it the material of choice for turbine blades, discs, and fasteners in gas turbine engines. Its ability to maintain mechanical properties at elevated temperatures is due to the precipitation of gamma prime (Ni₃(Ti, Al)) phases.
1. Basic Information of 660 (A286)
A286 is an austenitic iron-nickel-chromium superalloy that is strengthened by a combination of solid-solution and precipitation hardening. It is typically solution-treated at 980°C (1800°F) and then aged at 720°C (1325°F) for 16 hours to precipitate the hardening phase. The alloy exhibits excellent notch-rupture strength and is resistant to oxidation and corrosion up to 700°C. It is non-magnetic in the annealed condition and slightly magnetic after cold work.
2. Chemical Composition
The composition of A286 is carefully balanced to provide high-temperature strength while maintaining fabricability. Titanium and aluminum are the key precipitation-hardening elements, while molybdenum enhances solid-solution strengthening.
| Element | Composition Range (wt%) |
|---|---|
| Carbon (C) | ≤ 0.08 |
| Manganese (Mn) | ≤ 2.00 |
| Silicon (Si) | ≤ 1.00 |
| Chromium (Cr) | 13.50 – 16.00 |
| Nickel (Ni) | 24.00 – 27.00 |
| Molybdenum (Mo) | 1.00 – 1.50 |
| Titanium (Ti) | 1.90 – 2.35 |
| Aluminum (Al) | ≤ 0.35 |
| Vanadium (V) | 0.10 – 0.50 |
| Boron (B) | 0.001 – 0.010 |
| Phosphorus (P) | ≤ 0.040 |
| Sulfur (S) | ≤ 0.030 |
| Iron (Fe) | Balance |
3. Mechanical Properties
The mechanical properties of A286 are specified at both room temperature and elevated temperatures. The data below represents the standard solution-treated and aged condition (per AMS 5731/5737).
| Temperature | Tensile Strength (MPa) | Yield Strength 0.2% (MPa) | Elongation (%) | Hardness (HRC) |
|---|---|---|---|---|
| Room Temperature (20°C) | ≥ 1000 | ≥ 690 | ≥ 15 | 32 – 38 |
| 540°C (1000°F) | ≥ 830 | ≥ 620 | ≥ 12 | N/A |
| 650°C (1200°F) | ≥ 690 | ≥ 550 | ≥ 10 | N/A |
4. Typical Applications in Turbine Engines
A286 is specifically designed for high-temperature applications in the hot section of gas turbine engines. Its key applications include:
- Turbine blades: Low-pressure turbine blades where temperatures do not exceed 700°C, requiring high creep strength and thermal fatigue resistance.
- Turbine discs: Forged discs in the intermediate-pressure section, where the alloy’s high yield strength prevents deformation under centrifugal loads.
- Fasteners: Bolts and nuts for casing and flange connections, where relaxation resistance at temperature is critical.
- Afterburner components: Flame holders and liners exposed to high thermal gradients.
- CNC machined parts: Precision-machined fuel nozzles, sensor housings, and actuator components for engine control systems.
5. CNC Machining Performance
A286 is classified as a difficult-to-machine material due to its high work-hardening rate, low thermal conductivity, and tendency to form built-up edge (BUE). Machining is typically performed in the solution-treated condition (annealed) before aging. After aging, only finish machining is recommended.
| Operation | Cutting Speed (m/min) | Feed (mm/rev) | Depth of Cut (mm) | Tool Material |
|---|---|---|---|---|
| Turning (Annealed) | 40 – 60 | 0.10 – 0.25 | 1.0 – 3.0 | Carbide (K20/K30, TiAlN coated) |
| Turning (Aged) | 20 – 35 | 0.05 – 0.12 | 0.2 – 1.0 | Ceramic (SiAlON) or CBN |
| Milling (Annealed) | 30 – 50 | 0.08 – 0.15 (per tooth) | 0.5 – 2.0 | Carbide (AlTiN coated, variable helix) |
| Drilling | 10 – 20 | 0.03 – 0.08 | N/A | HSS-Co (M42) or Carbide |
Key Machining Tips:
- Use high-pressure coolant (minimum 70 bar) directed at the cutting zone to reduce heat buildup.
- Maintain a constant feed rate; any interruption can cause work hardening and tool chipping.
- For tapping, use spiral-flute taps with TiCN coating; pre-drill at 65-70% thread depth to reduce torque.
- Surface finish in the annealed condition can achieve Ra ≤ 0.8 µm; in aged condition, Ra ≤ 0.4 µm with CBN tools.
6. Our Services
Dongguan Stirling Metal Products Co., Ltd. specializes in providing 660 material + CNC machining One-Stop Service:
- ✅ Material procurement: genuine product guarantee, complete material certificates (MTC per AMS 5731/5737)
- ✅ CNC machining: accuracy ±0.01mm, surface finish down to Ra 0.2 µm
- ✅ Heat treatment: In-house solution annealing and aging with vacuum furnace for minimal oxidation
- ✅ Sample production: fast delivery in 3-5 days for prototype validation
- ✅ Batch production: delivery time of 7-15 days with full traceability and NDT reports
Free Quote consultation, welcome to contact us!
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