COMPREHENSIVE TECHNICAL ANALYSIS AND DATASHEET OF INCONEL 660 / ALLOY 660 (UNS S66286) FASTENING SYSTEMS
Inconel 660 (widely known in the industry as Alloy 660 or A-286) is a precipitation-hardening, iron-nickel-chromium superalloy. Designed specifically for applications requiring high strength and robust oxidation resistance at elevated temperatures, this alloy performs exceptionally well in continuous service environments up to 1300°F (704°C).
While marketed under the "Inconel" or "Alloy" 660 banner, it is technically a highly alloyed austenitic stainless steel that leverages Titanium and Aluminum to undergo precipitation hardening. This thermal aging process locks the microstructural lattice, giving Alloy 660 immense yield strength and unparalleled stress-rupture capabilities. It is the premier fastening solution for jet engine components, industrial gas turbines, and extreme high-temperature exhaust manifolds.
■ Product Overview & Specifications
Alloy 660 fastening systems are typically supplied in various heat-treated classes (such as Class A, B, C, or D per ASTM A453) to balance ductility with high-temperature tensile strength.
| Material Classification | Precipitation-Hardenable Iron-Nickel-Chromium Superalloy |
|---|---|
| UNS Designation | S66286 (Alloy 660 / A286) |
| Microstructure | Austenitic Matrix with Precipitation Hardened Phases |
| Magnetic State | Non-Magnetic (Retains low permeability after cold working) |
| Density | ~7.92 g/cm³ (0.286 lb/in³) |
| Size Range | Metric: M6 to M100 | Imperial: 1/4" to 4" Custom 12-point aerospace bolts and heavy hex studs available. |
| Thread Types | UNC, UNF, 8UN, Metric Coarse, Metric Fine (Rolled threads strictly recommended) |
| Strengthening Method | Solution Annealing + Precipitation Hardening (Aging) |
■ Proprietary Datasheet Download (GATED)
Access professional-grade technical data for Inconel / Alloy 660, including detailed stress-rupture (100-hour min at 1200°F) compliance charts, elevated temperature yield data, and aerospace AMS specification cross-references.
Alloy 660 / Inconel 660 (S66286) — Complete Technical Datasheet
Contains comprehensive Class A through D mechanical comparisons, high-temperature thermal expansion metrics, and critical anti-galling installation torques.
⬇ DOWNLOAD DATASHEET■ MTC Integration Section
To guarantee the alloy's survival under extreme thermal stress, Ananka Group provides absolute metallurgical verification mapping back to the original melt.
- EN 10204 Type 3.1: Mandatory reporting of actual chemical analysis, mechanical property verification, and the required 100-hour stress-rupture test results as dictated by ASTM A453.
- EN 10204 Type 3.2: Third-party witness testing (e.g., ABS, DNV GL, TUV) facilitated for critical aerospace, offshore, and high-pressure turbine fastening packages.
■ Chemical Composition (UNS S66286)
The alloy features a high Nickel and Chromium base for excellent oxidation and corrosion resistance, while the careful balance of Titanium, Aluminum, and Vanadium forms the intermetallic compounds necessary for its high-temperature strength.
| Nickel (Ni) | Chromium (Cr) | Titanium (Ti) | Moly (Mo) | Manganese (Mn) | Vanadium (V) | Aluminum (Al) |
|---|---|---|---|---|---|---|
| 24.0 – 27.0 | 13.5 – 16.0 | 1.90 – 2.35 | 1.00 – 1.50 | 2.00 Max | 0.10 – 0.50 | 0.35 Max |
*Silicon (1.00 Max) and Carbon (0.08 Max) are controlled. Trace amounts of Boron (0.001–0.010) are added specifically to enhance high-temperature creep strength.
■ Mechanical Properties (By Class)
The final mechanical properties of Inconel 660 are dictated by the specific heat treatment applied. Class A and B are standard for heavy bolting, while Class D is utilized for maximum yield strength.
| Property | Class A, B & C (Typical) | Class D (High Strength) |
|---|---|---|
| Tensile Strength (Min) | 130 ksi (895 MPa) | 130 ksi (895 MPa) |
| Yield Strength (0.2% Offset, Min) | 85 ksi (585 MPa) | 105 ksi (725 MPa) |
| Elongation in 2" (Min) | 15% | 15% |
| Hardness (Brinell) | 248 to 341 HBW | 248 to 341 HBW |
| Stress Rupture (1200°F / 650°C) | 100 Hours Min (No Rupture) | 100 Hours Min (No Rupture) |
■ Equivalent Grades & Designations
| Standard / System | Designation |
|---|---|
| UNS Designation | S66286 |
| Common Trade Name | Inconel 660, Alloy 660, A-286 |
| ASTM Specifications | ASTM A453 Grade 660 (Classes A, B, C, D) |
| European Equivalent | EN 1.4980 / X6NiCrTiMoVB25-15-2 |
| Aerospace Specs | AMS 5731, AMS 5732, AMS 5737 |
■ Applications & Industries
Alloy 660 is the definitive fastening choice when standard 300-series stainless steels suffer rapid creep deformation or high-temperature oxidation failure.
- Aerospace & Defense: Jet engine turbine components, afterburner fasteners, and high-stress missile hardware.
- Power Generation: Heavy-duty fastening for industrial gas turbines, superchargers, and high-temperature steam lines.
- Oil & Gas (Offshore): High-Pressure High-Temperature (HPHT) subsea wellhead fastening and flare boom structures.
- Automotive / Motorsport: High-performance racing engine exhaust manifold bolting and turbocharger studs.
■ Compatible Fastener Assemblies
To avoid galvanic corrosion and ensure that the entire joint assembly undergoes identical thermal expansion during heating and cooling cycles, mating components must match metallurgically.
| External Threads (Alloy 660) | Recommended Mating Component (Nuts) |
|---|---|
| Alloy 660 (A286) Stud Bolts | Alloy 660 (A286) Heavy Hex Nuts |
| Alloy 660 (A286) 12-Point Aerospace Bolts | Alloy 660 (A286) 12-Point / Hex Nuts |
■ Torque & Installation Guidelines
Alloy 660 has an austenitic base and is exceptionally prone to severe thread galling (cold welding). High-performance, high-temperature anti-seize pastes (Nickel or MoS2 based) are strictly mandatory during assembly to prevent thread stripping.
| Nominal Diameter | Threads Per Inch (UNC) | Target Torque — Lubricated (ft-lbs) |
|---|---|---|
| 1/2" | 13 | 45 - 55 |
| 5/8" | 11 | 90 - 110 |
| 3/4" | 10 | 150 - 180 |
| 1" | 8 | 380 - 420 |
■ Why Choose Ananka Group?
Ananka Group operates at the pinnacle of high-temperature alloy manufacturing, ensuring that your extreme-environment infrastructure remains secure.
- Precision Thread Rolling: Threads are rolled rather than cut whenever possible, significantly increasing cyclic fatigue resistance for turbine applications.
- Mandatory Stress-Rupture Testing: Full internal compliance with ASTM A453 stress-rupture testing requirements to guarantee high-temperature stability.
- Custom Aerospace Machining: CNC capabilities for specialized profiles, 12-point flange bolts, and custom socket head cap screws.
- 100% Traceability: Every fastener is heat-lot tracked and mapped directly back to premium steel mill certificates.
■ Frequently Asked Questions
1. Is Inconel 660 a true "Inconel"?
Technically, no. "Inconel" is a trademark generally applied to nickel-based superalloys (like Inconel 718 or 625). Alloy 660 is an iron-based superalloy (roughly 25% Nickel). However, due to its exceptional high-temperature performance, it is frequently marketed and referred to as "Inconel 660" in the fastener and aerospace industries.
2. What is the difference between Class A and Class D in ASTM A453 Grade 660?
The classes represent different heat treatment cycles. Class A undergoes a standard solution and aging process, providing high ductility with a minimum yield of 85 ksi. Class D undergoes a more aggressive dual-aging process to achieve a higher minimum yield strength of 105 ksi for maximum load-bearing capacity.
3. Is Alloy 660 magnetic?
No. Because its base microstructure is fully austenitic, Alloy 660 remains completely non-magnetic, even after aggressive cold working, machining, or thermal aging.
4. Can Alloy 660 be used in sub-zero or cryogenic environments?
Yes. While it is famous for operating reliably up to 1300°F (704°C), its austenitic structure means it does not suffer from a ductile-to-brittle transition. It retains excellent toughness, strength, and ductility at extreme cryogenic temperatures.