Product Overview
The alloy is also known as AISI 660, Grade 660, ASTM A453 Grade 660, and is widely used for high-temperature bolting and fastener applications where both strength and oxidation resistance are required. Inconel 660 is a precipitation-hardening alloy that achieves exceptional strength through a controlled aging heat treatment. Compared to standard stainless steels, Grade 660 provides significantly higher creep-rupture strength and superior oxidation resistance at elevated temperatures, making it a standard material for jet engine components, turbine fasteners, and high-performance automotive applications.
What is Inconel 660?
Inconel 660 is an iron-based nickel-chromium superalloy strengthened by precipitation of γ' [Ni₃(Al,Ti)] phase during aging heat treatment. The alloy contains approximately 24-27% nickel, 13.5-16% chromium, and additions of titanium (1.9-2.35%), aluminum (0.10-0.35%), molybdenum (1.0-1.5%), and vanadium (0.10-0.50%). It is designed for applications requiring high strength up to 700°C with good resistance to oxidation and corrosion.
Grade 660 is known for:
- High temperature strength up to 704°C (1300°F)
- Excellent creep-rupture resistance at elevated temperatures
- Precipitation hardenable through standard aging heat treatment
- Good oxidation resistance up to 815°C
- Resistance to stress relaxation at high temperatures
- Non-magnetic properties
- Good fabricability and machinability
Chemical Composition
| Element | UNS S66286 (ASTM) | SUH660 (JIS) | GH2132 (GB) | Role |
| Nickel (Ni) | 24.0 – 27.0 | 24.0 – 27.0 | 24.0 – 27.0 | Austenite stabilizer, corrosion resistance |
| Chromium (Cr) | 13.5 – 16.0 | 13.5 – 16.0 | 13.5 – 16.0 | Oxidation resistance, carbide former |
| Molybdenum (Mo) | 1.0 – 1.5 | 1.0 – 1.5 | 1.0 – 1.5 | Solid solution strengthening |
| Titanium (Ti) | 1.90 – 2.35 | 1.90 – 2.35 | 1.90 – 2.35 | γ' precipitation, age hardening |
| Aluminum (Al) | 0.10 – 0.35 | ≤ 0.35 | ≤ 0.35 | γ' precipitation |
| Vanadium (V) | 0.10 – 0.50 | 0.10 – 0.50 | 0.10 – 0.50 | Grain refinement, carbide former |
| Boron (B) | 0.003 – 0.010 | 0.001 – 0.010 | 0.001 – 0.010 | Grain boundary strengthening |
| Cobalt (Co) | ≤ 1.00 | ≤ 1.00 | ≤ 1.00 | Residual element |
| Iron (Fe) | Balance | Balance | Balance | Base element |
| Carbon (C) | ≤ 0.08 | ≤ 0.08 | ≤ 0.08 | Carbide former |
| Silicon (Si) | ≤ 1.00 | ≤ 1.00 | ≤ 1.00 | Deoxidizer |
| Manganese (Mn) | ≤ 2.00 | ≤ 2.00 | ≤ 2.00 | Deoxidizer |
| Phosphorus (P) | ≤ 0.025 | ≤ 0.040 | ≤ 0.030 | Impurity |
| Sulfur (S) | ≤ 0.025 | ≤ 0.030 | ≤ 0.020 | Impurity |
Mechanical Properties
Annealed Condition (Solution Treated)
| Property | ASTM A453 Grade 660 |
| Tensile Strength | ≤ 724 MPa (105 ksi) |
| Elongation | ≥ 25% |
| Hardness | ≤ 91 HRB |
Aged Condition (Precipitation Hardened)
| Property | ASTM A453 Grade 660 | Typical Achieved |
| Tensile Strength | ≥ 965 MPa (140 ksi) | 1,000 – 1,100 MPa |
| Yield Strength (0.2% Offset) | ≥ 655 MPa (95 ksi) | 700 – 800 MPa |
| Elongation | ≥ 15% | 18 – 25% |
| Hardness | 24 – 35 HRC | 28 – 32 HRC |
| Creep Strength (650°C, 100h) | ≈ 240 MPa | |
| Creep Strength (700°C, 100h) | ≈ 210 MPa |
Physical Properties
| Property | Value |
| Density | 7.95 g/cm³ |
| Melting Range | 1371 – 1427°C |
| Thermal Conductivity | 15.0 W/m·K at 150°C |
| Coefficient of Thermal Expansion (20-100°C) | 16.8 × 10⁻⁶/°C |
| Elastic Modulus | 201 GPa |
| Magnetic Permeability | Non-magnetic |
Key Advantages of Inconel 660
High Temperature Strength – Inconel 660 maintains high tensile, fatigue, and creep-rupture strength up to 704°C. The γ' precipitation strengthening mechanism provides superior high-temperature strength compared to standard austenitic stainless steels. The alloy is commonly used for turbine bolts and fasteners where relaxation resistance is critical.
Excellent Creep-Rupture Resistance – The alloy exhibits outstanding creep resistance at elevated temperatures. The creep-rupture life at 650°C exceeds 1,000 hours under moderate stress, making it a reliable material for long-term high-temperature service applications.
Good Oxidation and Corrosion Resistance – With 13.5-16% chromium content, Inconel 660 provides good resistance to oxidation, scaling, and high-temperature corrosion. The alloy performs well in oxidizing environments up to 815°C and resists various corrosive media.
Precipitation Hardenable – Inconel 660 can be precipitation hardened through aging heat treatment. The standard aging cycle (675-705°C, 12-16 hours) develops optimal mechanical properties and provides excellent stress relaxation resistance, which is critical for bolting applications.
Good Fatigue Resistance – The alloy offers excellent resistance to fatigue and thermal fatigue, making it suitable for components subject to cyclic loading at elevated temperatures. This is particularly important for turbine applications and engine components.
Excellent Workability and Machinability – Inconel 660 has better machinability than many other superalloys. It can be readily forged, hot worked, and cold worked. The alloy is weldable using TIG, MIG, and resistance welding with appropriate filler metals.
Grade 660 vs. Inconel 718: Comparison
| Property | Inconel 660 (Grade 660) | Inconel 718 |
| Base Element | Iron (balance) with 24-27% Ni | Nickel (50-55%) with 18-20% Fe |
| Strengthening Phase | γ' (Ni₃(Al,Ti)) | γ' (Ni₃Al) + γ'' (Ni₃Nb) |
| Tensile Strength (aged) | ≥ 965 MPa | ≥ 1,240 MPa |
| Temperature Capability | Up to 704°C | Up to 700°C |
| Key Applications | Turbine bolts, fasteners, studs, jet engine components | Turbine disks, rocket motors, HPHT oil and gas |
| Cost | More economical | Higher |
When to choose Grade 660: Applications requiring high-temperature bolting and fastening, jet engine components, turbine bolts, and high-performance automotive where cost is a factor and high strength up to 700°C is required.
When to choose Inconel 718: Applications requiring maximum high-temperature strength, fracture toughness, and creep resistance at temperatures up to 700°C where cost is less of a concern.
Heat Treatment of Inconel 660
Inconel 660 is a precipitation-hardenable alloy that requires specific heat treatment to achieve optimal mechanical properties:
Solution Annealing (Condition A):
- Temperature: 980 – 1010°C (1800 – 1850°F)
- Soaking Time: 1 hour
- Cooling: Rapid cooling (oil or water quench)
- Purpose: Dissolve all precipitates, achieve single-phase austenite
- Result: Soft, workable condition, ready for forming and machining
Precipitation Hardening (Aging – Condition B):
- Temperature: 675 – 705°C (1250 – 1300°F)
- Soaking Time: 12 – 16 hours
- Cooling: Air cool
- Purpose: Form Ni₃(Al,Ti) γ' precipitates for strengthening
- Result: Maximum strength and creep resistance
Double Aging (Alternative):
- First Stage: 705°C for 16 hours, furnace cool to 620°C
- Second Stage: 620°C for 16 hours, air cool
- Purpose: Optimize stress relaxation resistance for bolting applications
Available Product Forms from Womic Steel
Seamless Pipe & Seamless Tube
- Outside Diameter: 6mm – 200mm
- Wall Thickness: 1mm – 25mm
- Length: Up to 12m
- Standards: ASTM B639, ASTM B983, AMS 5731, AMS 5732, AMS 5737, AMS 5895
- Applications: High-temperature process piping, heat exchanger tubes, instrumentation lines, aerospace tubing
- Keywords: Inconel 660 seamless pipe, Grade 660 tube, UNS S66286 pipe, SUH660 tube, 1.4980 seamless pipe
Steel Bar (Round, Square, Flat, Hex)
- Diameter: 6mm – 300mm
- Surface: Hot rolled, Bright (cold drawn), Ground, Turned
- Standards: ASTM A453, ASTM B639, AMS 5731, AMS 5732, AMS 5734, AMS 5737
- Applications: Turbine bolts, fasteners, studs, shafts, valve stems, machining stock
- Keywords: Inconel 660 round bar, Grade 660 bar, SUH660 rod, ASTM A453 Grade 660, high temperature fasteners
Steel Plate & Sheet
- Thickness: 1mm – 100mm
- Width: Up to 2000mm
- Standards: AMS 5525, AMS 5858
- Applications: Pressure vessel components, structural parts, flange blanks
- Keywords: Inconel 660 plate, Grade 660 sheet, alloy plate, high temperature plate
Steel Coil & Strip
- Thickness: 0.5mm – 4.0mm
- Width: 10mm – 1000mm
- Standards: AMS 5525
- Applications: Formed components, bellows, stampings
- Keywords: Inconel 660 coil, strip, high temperature strip
Flanges & Fittings
- Types: Weld Neck, Slip-On, Blind, Socket Weld, Threaded
- Sizes: 1/2" – 24"
- Pressure Rating: Class 150 – Class 2500
- Standards: ASTM A453, ASME B16.5
- Keywords: Inconel 660 flanges, Grade 660 fittings
Forgings
- Types: Rings, disks, shafts, valve bodies, custom geometries
- Weight: Up to 3,000kg per piece
- Standards: ASTM A453, AMS 5731
- Keywords: Inconel 660 forging, forged ring, turbine component forging
Fasteners (Bolts, Nuts, Studs)
- Types: Hex bolts, Socket head cap screws, Stud bolts, Threaded rods, Nuts, Washers
- Sizes: M2 – M100, 1/4" – 4"
- Standards: ASTM A453 Grade 660, ASTM B637
- Applications: Turbine bolts, high-temperature flange connections, structural fasteners
- Keywords: Inconel 660 bolts, Grade 660 stud bolts, high temperature fasteners, turbine bolts
Grade 660 Valves
- Types: Ball valves, Gate valves, Globe valves, Check valves
- Sizes: 1/2" – 12"
- Pressure Rating: Class 150 – Class 2500
- Temperature Range: -196°C to +704°C
- Design Standards: API 608, API 6D, ASME B16.34
- Actuation: Manual, Pneumatic, Electric
- Applications: High-temperature process isolation, turbine steam lines, gas turbine control
Applications of Inconel 660
Aerospace – Inconel 660 is extensively used in jet engine and gas turbine components including turbine bolts, compressor disks, turbine casings, afterburner parts, thrust reversers, and engine mounting hardware. Its combination of high-temperature strength, fatigue resistance, and oxidation resistance makes it ideal for critical aerospace applications. The alloy is standard material for jet engine bolts and fasteners operating at temperatures up to 700°C.
Gas Turbine Power Generation – The alloy is used for turbine bolts, studs, and fasteners in industrial gas turbines, steam turbines, and combined cycle power plants. Its resistance to stress relaxation at elevated temperatures ensures reliable bolted connections through extended service life.
Automotive – Inconel 660 is used in turbocharger housings, exhaust manifolds, diesel engine components, and high-performance automotive fasteners. Its ability to withstand exhaust gas temperatures and thermal cycling makes it suitable for modern high-performance and turbocharged engines.
Nuclear Power – The alloy is used in nuclear reactor components, core internals, control rod mechanisms, and high-temperature fasteners requiring long-term reliability and resistance to neutron irradiation.
Petrochemical Processing – Inconel 660 is used in high-temperature chemical reactors, reformer tubes, furnace components, and process piping requiring strength and oxidation resistance at elevated temperatures.
High-Temperature Bolting – Grade 660 is the standard material for high-temperature bolting applications. ASTM A453 Grade 660 bolts and studs are widely specified for pressure vessel flanges, turbine casings, and high-temperature piping connections requiring resistance to creep and stress relaxation.
Standards & Specifications
| Standard | Description |
| UNS Designation | S66286 |
| Werkstoff Number | 1.4980 |
| AISI/SAE | 660 |
| ASTM A453 | Standard specification for high-temperature bolting |
| ASTM B639 | High-temperature alloy bar/rod |
| AMS 5525 | Plate/sheet/strip |
| AMS 5731 | Bar, wire, forgings |
| AMS 5732 | Bar, wire, forgings |
| AMS 5734 | Bar, wire, forgings |
| AMS 5737 | Pipe and tube |
| AMS 5895 | Bar, wire, forgings |
| JIS | SUH660 |
| GB/T | GH2132 |
| European | 1.4980 / X6NiCrTiMoV25-15-2 |
| ISO | X6NiCrTiMoV25-15-2 |
Frequently Asked Questions
Q: What is Inconel 660?
A: Inconel 660 (UNS S66286 / SUH660 / GH2132) is an iron-based precipitation-hardening superalloy with excellent high-temperature strength up to 704°C. It is strengthened by γ' precipitation through aging heat treatment and is widely used for turbine bolts, fasteners, and jet engine components.
Q: What is the difference between Grade 660 and Inconel 718?
A: Inconel 660 is iron-based (with 24-27% Ni, balance Fe) with tensile strength ≥ 965 MPa, while Inconel 718 is nickel-based (50-55% Ni) with tensile strength ≥ 1,240 MPa. Grade 660 is more economical and widely used for bolting; Inconel 718 is used for maximum strength applications.
Q: What is the maximum service temperature for Inconel 660?
A: Inconel 660 is rated for continuous service up to 704°C (1300°F). For oxidation resistance, short-term excursions up to 815°C (1500°F) are possible. Creep strength decreases significantly above 700°C.
Q: Is Inconel 660 readily weldable?
A: Yes, Inconel 660 can be welded using TIG, MIG, and resistance welding processes. However, welding requires careful control of heat input and filler metal selection to avoid hot cracking. Post-weld solution annealing and aging may be required to restore mechanical properties.
Q: What are the Chinese equivalents of Inconel 660?
A: The Chinese equivalent of Inconel 660 is GH2132 (高温合金) for aerospace and high-temperature applications, and the Japanese equivalent is SUH660.
Q: What product forms are available for Inconel 660?
A: Womic Steel supplies Inconel 660 in seamless pipe, welded pipe, steel bar, steel plate, steel coil, strip, flanges, fittings, forgings, wire, fasteners, and valves. Complete product specifications and size ranges are listed in the product availability section.
Q: Does Inconel 660 require heat treatment?
A: Yes. Inconel 660 requires solution annealing (980-1010°C) followed by aging (675-705°C for 12-16 hours) to achieve optimal mechanical properties. The aging treatment precipitates γ' phase for strengthening.
Contact Womic Steel
Website: www.womicsteel.com
E-mail: sales@womicsteel.com
Tel / WhatsApp / WeChat:
Victor: +86 15575100681
Jack: +86 18390957568
Womic Steel – Your reliable partner for Inconel 660 / Grade 660 (UNS S66286, SUH660, GH2132) seamless pipe, steel bar, steel plate, steel coil, flanges, fittings, forgings, and fasteners for aerospace, gas turbine, power generation, and high-temperature bolting applications worldwide. Full traceability, classification society certification, and EN 10204 Type 3.1/3.2 documentation available.
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